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Internet Book of Critical Care (IBCC)

Online Medical Education on Emergency Department (ED) Critical Care, Trauma, and Resuscitation

Posterior Reversible Encephalopathy Syndrome (PRES)

June 24, 2022 by Josh Farkas

• Pathogenesis
• Clinical presentation
• PRES-RCVS (Reversible Cerebral Vasoconstriction Syndrome) overlap
• Lumbar puncture
• EEG & seizure semiology
• Differential diagnosis
• Questions & discussion

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• Brain injury is not always reversible.
• Involvement is not always localized to the posterior regions of the brain, nor to the white matter.
• PRES is a clinicoradiologic diagnosis that was not discovered until the widespread application of brain imaging modalities such as CT and MRI.
• PRES often occurs in the context of a hypertensive emergency, in which case PRES is equivalent to “hypertensive encephalopathy.”
• The exact incidence of PRES is unclear, but this is commonly encountered within the ICU.

three dimensions of pathogenesis

• Note: High-quality evidence on the pathogenesis of PRES is lacking. Consequently, the following is largely hypothetical in nature.
• Normally, the cerebral arterioles will vasoconstrict in the context of hypertension, thereby shielding the brain tissue from experiencing hypertension.
• At extremely high blood pressures, autoregulation may fail, causing the brain tissue to experience very high blood pressures. Hypertension may lead to fluid exudation and tissue edema.
• Both the absolute blood pressure and the rate of blood pressure rise are important. Patients with chronic hypertension can tolerate extremely high blood pressures without developing PRES. Alternatively, patients with baseline hypotension or highly labile blood pressures may be more likely to develop PRES.
• Posterior regions of the brain may be more susceptible to failed autoregulation, because the vasculature has less sympathetic innervation. ( 33630183 )
• Dysfunction of the vascular endothelium may promote exudation of fluid from the vasculature and tissue edema.
• Endothelial dysfunction may be especially relevant in the context of cytotoxic chemotherapies or preeclampsia.
• In occasional patients, dysfunctional attempts at autoregulation may result in reactive focal vasoconstriction. This may lead to focal hypoperfusion and infarction.
• When focal vasoconstriction occurs, this may represent a combined syndrome involving both PRES and reversible cerebral vasoconstriction syndrome (RCVS) – more on this below .

varying pathogenesis in different patients

• In some patients, the primary mechanism of PRES may be failure of autoregulation (#1 above). For example, this may be the case in patients with hypertensive emergency.
• In other patients, endothelial dysfunction alone could be the cause of PRES. This may explain how PRES can occur in patients who are not hypertensive.

hypertension is the most common contributing factor

• The key contributing factor is a rapid increase in blood pressure above the patient's baseline that overwhelms cerebral autoregulation.
• ⚠️ ~25% of patients lack any documented hypertension. Thus, a normal or low blood pressure does not exclude PRES. ( 35046115 )
• (1) Hypertensive emergency due to uncontrolled chronic hypertension. “Hypertensive encephalopathy” is one subgroup of PRES patients.
• (2) Preeclampsia/eclampsia . 98% of patients with eclampsia in one series had PRES on MRI scan. ( 33630183 ) Eclampsia thus represents a subgroup of patients with PRES.
• (3) Renal failure (e.g., glomerulonephritis). Renal failure may cause both hypertension and endothelial dysfunction.
• (4) Guillain-Barre syndrome with autonomic instability. 📖
• (5) Paroxysmal sympathetic hyperactivity (PSH). 📖

medications that cause hypertension and/or endothelial dysfunction

• Anthracyclines: adriamycin, daunorubicin.
• Antimetabolites : azathioprine, capecitabine, cytarabine, gemcitabine, nelarabine.
• Alkylating agent: ifosfamide, cyclophosphamide.
• Folate antagonists : 5-fluorouracil, methotrexate.
• Platinum analogues : cisplatin, carboplatin, oxaliplatin.
• Proteasome inhibitor: bortezomib.
• Taxenes (paclitaxel).
• Vinca alkaloids: vincristine, vinblastine, vinorelbine.
• Multidrug regimens for acute leukemia: L-asparaginase and intrathecal methotrexate.
• Intravenous immunoglobulin (IVIG).
• Calcineurin inhibitors ( tacrolimus , sirolimus, cyclosporine ).
• Mycophenolate mofetil.
• Rituximab .
• Steroids, especially high-dose.
• Checkpoint inhibitor ipilimumab and CAR T-cell therapy. ( 32487905 )
• Granulocyte colony stimulating factor (G-CSF).
• Interferon therapy. ( 35046115 )
• VEGF inhibitors (e.g., bevacizumab ).
• Tyrosine kinase inhibitors : sorafenib, sunitinib, erlotinib, vandetanib, pazopanib, lenvatinib.
• mTOR kinase inhibitor: temsirolimus.
• Sympathomimetics (therapeutic or illicit).
• Carbamazepine.
• LSD intoxication. ( 35046115 )

systemic inflammation & endothelial dysfunction

• Sepsis (septic patients with encephalopathy may have a prevalence of 9%). ( 35133605 )
• Autoimmune diseases , (e.g., lupus, scleroderma, Sjogren's disease, rheumatoid arthritis, ANCA vasculitides, neuromyelitis optica spectrum disorder). ( 35046115 )
• Thrombotic microangiopathies 📖 (e.g., hemolytic uremic syndrome, thrombotic thrombocytopenic purpura).

other risk factors

• Renal failure , both acute and chronic (promotes endothelial dysfunction & volume overload).
• Hypomagnesemia , hypercalcemia. ( 24476076 )
• Fluid overload .
• Sickle cell disease.
• Nephrotic syndrome. ( 35419136 )

Course: clinical deterioration is acute or subacute (may evolve over 1-2 days).

clinical features

• ⚠️ Absence of hypertension does not exclude PRES. ( 34618761 )
• Seizure (~70%) is very common (especially among ICU PRES cohorts). ( 35046115 ) More on seizure semiology below 📖 .
• Encephalopathy (~70%): Ranges from somnolence to coma.
• Usually described as constant, dull, diffuse, gradual onset, and difficult to treat.
• If a thunderclap headache occurs, this should suggest reversible cerebral vasoconstriction syndrome (RCVS) as either an alternative or superimposed diagnosis. 📖
• Auras, blurred vision, color vision abnormality, diplopia.
• Visual field deficits.
• Cortical blindness, visual hallucinations (Anton syndrome).
• Vary depending on the site of involvement.
• May include hemiparesis, aphasia, or ataxia. ( 33630183 )

basics of PRES-RCVS (Reversible Cerebral Vasoconstriction Syndrome) overlap

• PRES involves failure of autoregulation, with excess blood flow through the arterioles.
• RCVS involves excessive vasospasm, causing inadequate blood flow through the arterioles.
• (1) The most common form of PRES-RCVS overlap appears to occur in patients who initially present with PRES. Over time, cerebral vasculature responds to hypertension and endothelial damage with vasospasm , thereby causing RCVS to be superimposed on top of PRES . RCVS might complicate the majority of patients with PRES. ( 29274685 )
• (2) Less commonly, ~20% of RCVS may be complicated by the subsequent occurrence of PRES. ( 29274685 ) In these patients, the primary insult is RCVS – which leads to subsequent hypertension and sympathetic activation. This hypertension may overwhelm autoregulation in posterior areas of the brain which aren't experiencing vasoconstriction – leading to PRES. Essentially, the body is trying to overcome the cerebral vasoconstriction of RCVS, but this leads to an excessive blood pressure.

clinical features of PRES-RCVS overlap

• Papers on “RCVS” often note that some patients have cerebral edema.
• Papers on “PRES” often note that some patients have convexity subarachnoid hemorrhage.
• The table above shows more classic features of PRES and RCVS. Patients with substantial symptomatology and imaging features of both syndromes may have PRES-RCVS overlap.

treatment implications

• Patients with PRES-RCVS overlap may theoretically benefit from consideration of treating both disease processes.

the hallmark finding is vasogenic edema

• CT scan may be normal, but in more severe cases the edema will also be visible on CT scanning as hypodense areas within the white matter.
• Vasogenic should be seen in 100% of cases on MRI, as this is part of the definition of PRES.
• Contrast enhancement (~40%) may occur in a leptomeningeal pattern, a cortical pattern within regions of altered FLAIR signal, or a combination. ( 35046115 )

various patterns of edema distribution

• Neither the pattern nor severity of vasogenic edema are related to the severity of clinical symptoms. (Busl 2022)
• Parieto-occipital pattern (~50%) – Edema is predominantly along the MCA-PCA watershed, located within the parietal and occipital lobes. This edema usually spares the paramedian parts of the occipital lobe (which may help differentiate it from ischemic stroke)( figure a, below). Even when edema is present in unusual areas such as the brainstem, a parieto-occipital pattern is generally present as well.
• Superior frontal sulcus pattern (~25%) – Edema is predominantly along the ACA-MCA watershed, located in the depth of the superior frontal sulcus ( figure b, below).
• Holohemispheric watershed pattern (~25%) – Edema is located along anterior, posterior, medial, and lateral watershed zones ( figure c , below).
• Central pattern (~10%) – Edema is in the deep white matter, basal ganglia, thalami, brainstem, pons, and cerebellum ( figure d , below).

MRI findings of superimposed infarction

• PRES typically causes vasogenic edema, with a characteristic appearance on different MRI sequences as shown in the top row below.
• In ~20% of patients with PRES, small areas of brain tissue may become ischemic. This causes cytotoxic edema, which is marked on MRI by hyperintensity on DWI and hypointensity on ADC (the red circle in the figure below). ( 31582040 ) Areas of hypointensity on ADC have greater specificity for ischemia that will progress to tissue infarction. This is a poor prognostic sign. ( 33630183 )

intracranial hemorrhage

• Intracranial hemorrhage is found in ~10-25% of patients. ( 35046115 )
• Parenchymal hemorrhage may occur (either lobar hematoma or punctate microhemorrhages). GRE/SWI sequences may reveal microhemorrhages in up to 65% of patients. ( 35046115 )
• Convexity subarachnoid hemorrhage may occur. This may suggest the coexistence of RCVS.

CT angiography (CTA) or MR angiography (MRA)

• These may be performed if there is concern for superimposed RCVS (e.g., based on MRI findings suggesting large areas of infarction, convexity subarachnoid hemorrhage, or focal neurologic deficits).
• Lumbar puncture is generally not required for the diagnosis of PRES. However, this may be necessary in some scenarios to exclude alternative diagnoses.
• Protein elevation may correlate with edema, as a marker of blood-brain barrier dysfunction.
• Opening pressure may be elevated.

clinical findings

• Seizures occur in ~70% of patients (and perhaps higher rates among patients sick enough to be in the ICU).
• Complex partial seizure may be the presenting symptom of PRES. ( 33630183 )
• Status epilepticus occurs in ~10%. This may be the presenting symptom. ( 35046115 )
• ⚠️ There should be a very low threshold to obtain continuous EEG monitoring for any patients with PRES who have altered mental status (especially if mental status abnormality is fluctuating, or seems disproportionate to the MRI abnormalities).(More on the indications for EEG here: 📖 )
• Focal sharp-wave discharges.
• Lateralized Periodic Discharges (LPDs 📖 ), often with a posterior distribution.
• Bilateral Independent Posterior Discharges (BIPDs 📖 ).
• Diffuse theta slowing is the most common finding. (Busl 2022)

management – see below 📖

• No single diagnostic test proves PRES (although MRI may be strongly suggestive).
• The above figure shows how this diagnosis is often approached, using a combination of clinical features, supportive evidence, and exclusion of other possibilities (section below). ( 28190431 )

The differential diagnosis will vary depending on any specific patient's imaging and clinical findings. However, the following list may include some reasonable considerations: ( 35046115 ; 34618761 )

• Reversible cerebral vasoconstriction syndrome (RCVS) – PRES and RCVS may coexist, so this differentiation may be impossible. 📖
• Demyelination (e.g., acute disseminated encephalomyelitis) – gadolinium enhancement in a ring-configuration may favor demyelination; microhemorrhages don't occur with demyelination; CSF with oligoclonal bands may favor demyelination. ( 35046115 )
• Progressive multifocal leukoencephalopathy (PML) 📖 – may be favored by immunosuppression, lesion asymmetry.
• Autoimmune or paraneoplastic encephalitis – may be favored by CSF pleocytosis, detection of autoantibodies.
• Viral encephalitis .
• SMART syndrome 📖 – favored by unilateral involvement, prominent gyral enhancement, history of radiation exposure.
• Toxic leukoencephalopathy (e.g., heroin).
• Acute hepatic encephalopathy – may cause FLAIR hyperintensity with reduced diffusion in the thalami, posterior limb of the internal capsule, and periventricular white matter. ( 35046115 )
• Osmotic demyelination syndrome 📖 – may be suggested by epidemiological risk factors, changes in osmolarity, prominent hyperintensity on diffusion weighted imaging (DWI).
• Cerebral venous thrombosis 📖 – may be suggested by edema, epidemiological factors, abnormal vascular imaging.

Treatment obviously focuses on management of blood pressure and seizures. However, the full treatment package may include five items:

(#1/5) Bp control

• MAP should be lowered by ~20-25% within 1-2 hours. ( 35046115 )
• A MAP target of 105-125 mm is often reasonable, although this may need to be personalized. ( 35046115 )
• Intravenous agents are initially preferred: Nicardipine infusion 💉 or clevidipine infusion 💉 .
• Oral calcium channel blockers may subsequently be utilized: Isradipine or nifedipine ER 💉 .
• ⚠️ Nitroglycerine should be avoided, as this may aggravate PRES. ( 30531559 )

(#2/5) seizure management

• Consider EEG monitoring in patients with altered consciousness (discussed above: 📖 )
• For most patients with PRES, a general antiseizure medication may be utilized (e.g., levetiracetam).
• Antiseizure medication may be tapered off as patients improve, often within a 1-2 week timeframe. (Busl 2022) However, 1-4% of patients may develop epilepsy and require longer term antiseizure medication. ( 35046115 )
• In some cases, these patterns combined with clinical features might reflect an electroclinical diagnosis of nonconvulsive status epilepticus (NCSE), which would warrant therapy. 📖

(#3/5) medication review & treatment of underlying cause(s)

• 💡PRES may result from a combination of several synergistic causes.
• This predominantly involves a medication review, to ensure that the patient isn't on any medications which may be causing PRES (listed above: 📖 ).

(#4/5) treat hypomagnesemia if present

• (a) Hypomagnesemia may contribute to PRES. ( 28054130 )
• (b) Magnesium is the only medication supported by RCT-level data for patients with PRES (noting that eclampsia is a subset of PRES).
• (c) Many patients may have an overlap of both PRES and RCVS; these patients may benefit from magnesium for treatment of RCVS.
• It's unknown whether intravenous magnesium could benefit most patients with PRES, but aggressive management of any hypomagnesemia seems sensible. More on the management of hypomagnesemia here: 📖 .

(#5/5) treat volume overload if present

• Among patients with hypertension and volume overload, the most effective “antihypertensive” agent is often furosemide. Blood pressure can be extremely difficult to manage in the face of uncontrolled volume overload.
• PRES involves tissue edema formation in the brain. Theoretically, edema resolution might be hastened if volume overload is managed.
• More on the management of volume overload & diuresis here: 📖 .

malignant PRES

• Malignant PRES is defined based on the presence of coma, deterioration despite standard management for elevated intracranial pressure, and radiological evidence of edema. ( 35046115 ) This isn't the usual trajectory for PRES, so alternative diagnoses should be considered (e.g., cerebral venous thrombosis, acute disseminated encephalomyelitis). 📖
• Management of intracranial pressure elevation. 📖 Rarely, severe swelling in the posterior fossa may cause obstructive hydrocephalus requiring temporary placement of an external ventricular drain.
• Aggressive treatment of any underlying condition (e.g., steroid for patients with underlying autoimmune disease).
• As a general rule, patients with PRES can look awful initially (e.g., due to brainstem involvement), yet subsequently make excellent recoveries. Recovery can take several days, so patience is required. Unfortunately, PRES can occasionally cause irreversible brain injury.
• Secondary intracranial hemorrhage in addition to PRES.
• Restricted diffusion on MRI, suggestive of cerebral infarction.
• Extensive cerebral edema. ( 35046115 )
• Patients may have recurrent episodes of PRES, especially if they have a persistent risk factor (e.g., sickle cell anemia, renal failure, or hypertension). ( 35046115 )

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To keep this page small and fast, questions & discussion about this post can be found on another page here .

• 20% of patients with PRES do not have hypertension – so don't assume that simply because a patient is normotensive that they do not have PRES.
• The management of PRES is more than simply reduction in blood pressure. For example, it is important to carefully consider why the patient has PRES and whether any contributory factors can be reversed.

Acknowledgement: Thanks to Dr. Richard Choi (@rkchoi) for thoughtful comments on this chapter.

Guide to emoji hyperlinks

• 24476076 Camara-Lemarroy CR, Gonzalez-Moreno EI, Ortiz-Corona Jde J, Yeverino-Castro SG, Sanchez-Cardenas M, Nuñez-Aguirre S, Villarreal-Alarcon MA, Galarza-Delgado DA. Posterior reversible encephalopathy syndrome due to malignant hypercalcemia: physiopathological considerations. J Clin Endocrinol Metab. 2014 Apr;99(4):1112-6. doi: 10.1210/jc.2013-3487 [ PubMed ]
• 28054130 Fischer M, Schmutzhard E. Posterior reversible encephalopathy syndrome. J Neurol. 2017 Aug;264(8):1608-1616. doi: 10.1007/s00415-016-8377-8 [ PubMed ]
• 28190431 Toledano M, Fugate JE. Posterior reversible encephalopathy in the intensive care unit. Handb Clin Neurol. 2017;141:467-483. doi: 10.1016/B978-0-444-63599-0.00026-0 [ PubMed ]
• 29274685 Arrigan MT, Heran MKS, Shewchuk JR. Reversible cerebral vasoconstriction syndrome: an important and common cause of thunderclap and recurrent headaches. Clin Radiol. 2018 May;73(5):417-427. doi: 10.1016/j.crad.2017.11.017 [ PubMed ]
• 31582040 Levitt A, Zampolin R, Burns J, Bello JA, Slasky SE. Posterior Reversible Encephalopathy Syndrome and Reversible Cerebral Vasoconstriction Syndrome: Distinct Clinical Entities with Overlapping Pathophysiology. Radiol Clin North Am. 2019 Nov;57(6):1133-1146. doi: 10.1016/j.rcl.2019.07.001 [ PubMed ]
• 32487905 Santomasso BD. Anticancer Drugs and the Nervous System. Continuum (Minneap Minn). 2020 Jun;26(3):732-764. doi: 10.1212/CON.0000000000000873 [ PubMed ]
• 32596758 Thakkar JP, Prabhu VC, Rouse S, Lukas RV. Acute Neurological Complications of Brain Tumors and Immune Therapies, a Guideline for the Neuro-hospitalist. Curr Neurol Neurosci Rep. 2020 Jun 29;20(8):32. doi: 10.1007/s11910-020-01056-0 [ PubMed ]
• 33273175 Lee EQ. Neurologic Complications in Patients With Cancer. Continuum (Minneap Minn). 2020 Dec;26(6):1629-1645. doi: 10.1212/CON.0000000000000937 [ PubMed ]
• 33630183 Gewirtz AN, Gao V, Parauda SC, Robbins MS. Posterior Reversible Encephalopathy Syndrome. Curr Pain Headache Rep. 2021 Feb 25;25(3):19. doi: 10.1007/s11916-020-00932-1 [ PubMed ]
• 34618761 Singhal AB. Posterior Reversible Encephalopathy Syndrome and Reversible Cerebral Vasoconstriction Syndrome as Syndromes of Cerebrovascular Dysregulation. Continuum (Minneap Minn). 2021 Oct 1;27(5):1301-1320. doi: 10.1212/CON.0000000000001037 [ PubMed ]
• 35046115 Triplett JD, Kutlubaev MA, Kermode AG, Hardy T. Posterior reversible encephalopathy syndrome (PRES): diagnosis and management. Pract Neurol. 2022 Jun;22(3):183-189. doi: 10.1136/practneurol-2021-003194 [ PubMed ]
• Busl KM, Dangayach N, Maciel CB (2022) : Neurointensive Care: The essentials . Presentation at the American Academy of Neurology Conference, Seattle 2022.
• 35419136 Niznick N, Lun R, Lelli DA, Fantaneanu TA. Clinical Problem Solving: Decreased Level of Consciousness and Unexplained Hydrocephalus. Neurohospitalist. 2022 Apr;12(2):312-317. doi: 10.1177/19418744211056781 [ PubMed ]

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Citation, DOI, disclosures and article data

At the time the article was created Frank Gaillard had no recorded disclosures.

At the time the article was last revised Frank Gaillard had no financial relationships to ineligible companies to disclose.

• Reversible posterior leukoencephalopathy syndrome
• Reversible posterior cerebral edema syndrome
• Hyperperfusion encephalopathy
• Occipito-parietal encephalopathy
• Reversible leukoencephalopathy
• Reversible posterior cerebral oedema syndrome
• PRES with spinal cord involvement
• Posterior eversible encephalopathy syndrome with spinal cord involvement
• Central PRES
• Central posterior reversible encephalopathy syndrome
• Posterior reversible encephalopathy syndrome (PRES)

Posterior reversible encephalopathy syndrome (PRES) , also known as reversible posterior leukoencephalopathy syndrome (RPLS) , is a neurotoxic state   that occurs secondary to the inability of the posterior circulation to autoregulate in response to acute changes in blood pressure . Hyperperfusion with resultant disruption of the blood-brain barrier  results in vasogenic edema , usually without infarction, most commonly in the parieto-occipital regions.

On this page:

Terminology, clinical presentation, radiographic features, treatment and prognosis, history and etymology, differential diagnosis.

• Cases and figures
• Imaging differential diagnosis

The term posterior reversible encephalopathy syndrome may be a misnomer as the syndrome:

can involve or extend beyond the posterior cerebrum

can progress to develop permanent cerebral injury and residual neurological defects, although most cases involve a resolution of changes and a clinical recovery with the treatment of the precipitating cause

may not present with encephalopathy in all patients

It should not be confused with chronic hypertensive encephalopathy , also known as hypertensive microangiopathy, which results in microhemorrhages in the basal ganglia, pons, and cerebellum.

Common presenting clinical features include 16,19 :

encephalopathy ( acute confusion  or altered mental state or decreased level of consciousness)

visual disturbance, including reversible cortical blindness 20

However, the presentation can be quite varied, and may include other neurological symptoms such as ataxia, focal neurological deficits, vertigo, or tinnitus 19 .

Although posterior reversible encephalopathy syndrome is most commonly thought of occurring as secondary to marked hypertension , this does not appear to be a necessary or sufficient explanation, given the very large and heterogeneous clinical scenarios that precipitate the development of posterior reversible encephalopathy syndrome and the fact that hypertension  is not present or does not reach the upper limits of self-regulation (140-160 mmHg) in 25% of patients.

The underlying mechanisms involved are not well understood but is thought to culminate in altered integrity of the blood-brain barrier . Three main precipitant theories have been proposed, that are not mutually exclusive 19 :

high blood pressure (breakthrough theory) leads to loss of self-regulation, hyperperfusion with endothelial damage and vasogenic edema

vasospasm theory results in local ischemia and hypoperfusion

endothelial dysfunction secondary to circulating endogenous or exogenous toxins

severe hypertension

eclampsia / pre-eclampsia

acute glomerulonephritis

hemolytic-uremic syndrome (HUS)

thrombocytopenic thrombotic purpura (TTP)

systemic lupus erythematosus (SLE)

drug toxicity

cyclophosphamide 10

erythropoietin

cyclosporine

azathioprine

L-asparaginase

filgrastim 15

ustekinumab 17,18

bone marrow or stem cell transplantation

solid organ transplantation

hyperammonemia

sickle cell disease   11

ventriculoperitoneal shunt insertion/overshunting   12

alcohol hepatitis 22

Microscopic appearance

during the acute course of PRES: vasogenic edema, without inflammation, ischemia, or neuronal damage 3

during the late course of PRES: demyelination and myelin pallor along with evidence of ischemia, anoxic neuronal damage, laminar necrosis, or older hemorrhage in the white matter and cortex 3

Typical posterior reversible encephalopathy syndrome manifests as bilateral vasogenic edema within the occipital and parietal regions (70-90% of cases), perhaps relating to the posterior cerebral artery supply. Despite its name, however, posterior reversible encephalopathy syndrome can be found in a non-posterior distribution, mainly in watershed areas, including within the frontal, inferior temporal, cerebellar, and brainstem regions 2,19 . Both cortical and subcortical locations are affected.

Uncommon patterns of posterior reversible encephalopathy syndrome in <5% include:

purely unilateral

central ("central PRES"): brainstem or basal ganglia involvement without cortical or subcortical white matter involvement

spinal cord involvement ("PRES-SCI")

Ischemic stroke , intracerebral hemorrhage , and subarachnoid hemorrhage are associated with posterior reversible encephalopathy syndrome in ~11%, ~10% and 7% of cases respectively 23 . The presence of contrast enhancement, no matter the pattern or how avid, does not portend the clinical outcome.

The affected regions, as outlined above, are hypoattenuating.

Angiography (DSA)

There may be signs of vasospasm or arteritis 3 :

diffuse vasoconstriction

focal vasoconstriction

vasodilatation

string-of-beads appearance

Signal characteristics of affected areas usually reflect vasogenic edema, with some exceptions.

T1: hypointense in affected regions

T1 C+ (Gd): patchy variable enhancement can be seen in ~35% of patients, in either a leptomeningeal or cortical pattern

T2:  hyperintense in affected regions

DWI: usually normal, sometimes hyperintense due to edema ( T2 shine-through ) or true restricted diffusion

ADC:  usually increased signal due to increased diffusion, but restricted diffusion is present in a quarter of cases 5

GRE/SWI: may show hemorrhages (including microhemorrhages ) in 9-50%  5

MRA: may show patterns of vasculopathy with vessel irregularity consistent with focal vasoconstrictions/vasodilatation and diffuse vasoconstriction 3

MRV: tends to be normal 3

Management is supportive, with discontinuation of any offending medication, gradual lowering of blood pressure, and antiseizure medications if appropriate 20 .

Posterior reversible encephalopathy syndrome was described for the first time as a distinct entity in 1996 by an American neurologist Judy Hinchey et al.  13 . Although others had previously described similar reversible CT and MRI findings in hypertension back to the 1980s 14 .

General imaging differential considerations include:

inflammatory cerebral amyloid angiopathy

edema usually centered on microhemorrhages

progressive multifocal leukoencephalopathy (PML)

periventricular and subcortical involvement, sparing the cortex

little or no mass effect or enhancement

severe hypoglycemia

posterior circulation infarct

occipital and cerebellar involvement

acute infarct demonstrates restricted diffusion; PRES with vasogenic edema alone does not restrict

hypertensive brainstem encephalopathy

absence of parieto-occipital involvement

gliomatosis cerebri

more asymmetric

sagittal sinus thrombosis

hypoxic-ischemic encephalopathy

SMART syndrome

Quiz questions

• 1. Foocharoen C, Tiamkao S, Srinakarin J et-al. Reversible posterior leukoencephalopathy caused by azathioprine in systemic lupus erythematosus. J Med Assoc Thai. 2006;89 (7): 1029-32. Pubmed citation
• 2. Bartynski WS, Boardman JF. Distinct imaging patterns and lesion distribution in posterior reversible encephalopathy syndrome. AJNR Am J Neuroradiol. 2007;28 (7): 1320-7. doi:10.3174/ajnr.A0549 - Pubmed citation
• 3. Bartynski WS. Posterior reversible encephalopathy syndrome, part 1: fundamental imaging and clinical features. AJNR Am J Neuroradiol. 2008;29 (6): 1036-42. doi:10.3174/ajnr.A0928 - Pubmed citation
• 4. Bartynski WS. Posterior reversible encephalopathy syndrome, part 2: controversies surrounding pathophysiology of vasogenic edema. AJNR Am J Neuroradiol. 2008;29 (6): 1043-9. doi:10.3174/ajnr.A0929 - Pubmed citation
• 5. Bartynski WS, Tan HP, Boardman JF et-al. Posterior reversible encephalopathy syndrome after solid organ transplantation. AJNR Am J Neuroradiol. 2008;29 (5): 924-30. doi:10.3174/ajnr.A0960 - Pubmed citation
• 6. Fugate JE, Claassen DO, Cloft HJ et-al. Posterior reversible encephalopathy syndrome: associated clinical and radiologic findings. Mayo Clin. Proc. 2010;85 (5): 427-32. doi:10.4065/mcp.2009.0590 - Free text at pubmed - Pubmed citation
• 7. McKinney AM, Short J, Truwit CL, McKinney ZJ, Kozak OS, SantaCruz KS, Teksam M. Posterior reversible encephalopathy syndrome: incidence of atypical regions of involvement and imaging findings. (2007) AJR. American journal of roentgenology. 189 (4): 904-12. doi:10.2214/AJR.07.2024 - Pubmed
• 8. McKinney AM, Sarikaya B, Gustafson C, Truwit CL. Detection of microhemorrhage in posterior reversible encephalopathy syndrome using susceptibility-weighted imaging. (2012) AJNR. American journal of neuroradiology. 33 (5): 896-903. doi:10.3174/ajnr.A2886 - Pubmed
• 9. Karia SJ, Rykken JB, McKinney ZJ, Zhang L, McKinney AM. Utility and Significance of Gadolinium-Based Contrast Enhancement in Posterior Reversible Encephalopathy Syndrome. (2016) AJNR. American journal of neuroradiology. 37 (3): 415-22. doi:10.3174/ajnr.A4563 - Pubmed
• 10. Jayaweera JL, Withana MR, Dalpatadu CK, Beligaswatta CD, Rajapakse T, Jayasinghe S, Chang T. Cyclophosphamide-induced posterior reversible encephalopathy syndrome (PRES): a case report. (2014) Journal of medical case reports. 8: 442. doi:10.1186/1752-1947-8-442 - Pubmed
• 11. Thust SC, Burke C, Siddiqui A. Neuroimaging findings in sickle cell disease. (2014) The British journal of radiology. 87 (1040): 20130699. doi:10.1259/bjr.20130699 - Pubmed
• 12. Merola J, Magdum S. An Unusual Complication following Ventriculoperitoneal Shunting. (2017) Journal of pediatric neurosciences. 12 (1): 61-63. doi:10.4103/1817-1745.205653 - Pubmed
• 13. Hinchey J, Chaves C, Appignani B, Breen J, Pao L, Wang A, Pessin MS, Lamy C, Mas JL, Caplan LR. A reversible posterior leukoencephalopathy syndrome. (1996) The New England journal of medicine. 334 (8): 494-500. doi:10.1056/NEJM199602223340803 - Pubmed
• 14. Hauser RA, Lacey DM, Knight MR. Hypertensive encephalopathy. Magnetic resonance imaging demonstration of reversible cortical and white matter lesions. (1988) Archives of neurology. 45 (10): 1078-83. doi:10.1001/archneur.1988.00520340032007 - Pubmed
• 15. Stübgen J. Posterior Reversible Encephalopathy Syndrome (PRES) After Granulocyte-Colony Stimulating Factor (G-CSF) Therapy: A Report of 2 Cases. J Neurol Sci. 2012;321(1-2):35-8. doi:10.1016/j.jns.2012.07.028 - Pubmed
• 16. Sudulagunta SR, Sodalagunta MB, Kumbhat M, Settikere Nataraju A. Posterior reversible encephalopathy syndrome(PRES). (2017) Oxford medical case reports. 2017 (4): omx011. doi:10.1093/omcr/omx011 - Pubmed
• 17. Gratton D, Szapary P, Goyal K, Fakharzadeh S, éronique Germain V, Saltiel P. Reversible Posterior Leukoencephalopathy Syndrome in a Patient Treated With Ustekinumab: Case Report and Review of the Literature. Arch Dermatol. 2011 Oct 1;147(10):1197–202. Available at https://jamanetwork.com/journals/jamadermatology/fullarticle/1105163
• 18. Mishra A & Seril D. Posterior Reversible Encephalopathy Syndrome Following Ustekinumab Induction for Crohn's Disease. Case Rep Gastroenterol. 2018;12(2):521-7. doi:10.1159/000492462 - Pubmed
• 19. Tetsuka S, Ogawa T. Posterior reversible encephalopathy syndrome: A review with emphasis on neuroimaging characteristics. (2019) Journal of the neurological sciences. 404: 72-79. doi:10.1016/j.jns.2019.07.018 - Pubmed
• 20. Bandyopadhyay S, Mondal K, Das S et al. Reversible Cortical Blindness: Posterior Reversible Encephalopathy Syndrome. J Indian Med Assoc. 2010;108(11):778-80. - Pubmed
• 21. Anderson R, Patel V, Sheikh-Bahaei N et al. Posterior Reversible Encephalopathy Syndrome (PRES): Pathophysiology and Neuro-Imaging. Front Neurol. 2020;11. doi:10.3389/fneur.2020.00463
• 22. John E, Sedhom R, Dalal I, Sharma R. Posterior Reversible Encephalopathy Syndrome in Alcoholic Hepatitis: Hepatic Encephalopathy a Common Theme. World J Gastroenterol. 2017;23(2):373-6. doi:10.3748/wjg.v23.i2.373 - Pubmed
• 23. Kaufmann J, Buecke P, Meinel T et al. Frequency of Ischaemic Stroke and Intracranial Haemorrhage in Patients with Reversible Cerebral Vasoconstriction Syndrome (RCVS) and Posterior Reversible Encephalopathy Syndrome (PRES) – A Systematic Review. Euro J of Neurology. 2024;:e16246. doi:10.1111/ene.16246 - Pubmed

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Article Contents

Introduction.

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Posterior reversible encephalopathy syndrome (PRES): presentation, diagnosis and treatment

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Anant Parasher, Rajat Jhamb, Posterior reversible encephalopathy syndrome (PRES): presentation, diagnosis and treatment, Postgraduate Medical Journal , Volume 96, Issue 1140, October 2020, Pages 623–628, https://doi.org/10.1136/postgradmedj-2020-137706

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Posterior reversible encephalopathy syndrome (PRES) is a neurological disorder which is characterised by variable symptoms, which include visual disturbances, headache, vomiting, seizures and altered consciousness. The exact pathophysiology of PRES has not been completely explained, but hypertension and endothelial injury seem to be almost always present. Vasoconstriction resulting in vasogenic and cytotoxic edema is suspected to be responsible for the clinical symptoms as well as the neuro-radiological presentation. On imaging studies, Symmetrical white matter abnormalities suggestive of edema are seen in the computer tomography (CT) and magnetic resonance imaging (MRI) scans, commonly but not exclusively in the posterior parieto-occipital regions of the cerebral hemispheres. The management is chiefly concerned with stabilization of the patient, adequate and prompt control of blood pressure, prevention of seizures and timely caesarean section in obstetric cases with pre-eclampsia/eclampsia. In conclusion, persistently elevated blood pressures remain the chief culprit for the clinical symptoms as well as the neurological deficits. Early diagnosis by diffusion weighted MRI scans, and differentiation from other causes of altered sensorium i.e. seizures, meningitis and psychosis, is extremely important to initiate treatment and prevent further complications. Although most cases resolve successfully and carry a favorable prognosis, patients with inadequate therapeutic support or delay in treatment may not project a positive outcome.

Posterior reversible encephalopathy syndrome (PRES) is a neurological disorder which is characterised by variable symptoms, which include visual disturbances, headache, vomiting, seizures and altered consciousness. 1 Its association is seen with a number of conditions including hypertension, pre-eclampsia and eclampsia, renal failure, systemic lupus erythematosus (SLE) and the use of some immunosuppressive agents. 2   3 PRES was first described in 1996 by Hinchey et al and shortly after the description, two other case series were published. 2   4 This condition has been known by various names previously (reversible posterior leukoencephalopathy syndrome, reversible posterior cerebral oedema syndrome and reversible occipital parietal encephalopathy), but PRES is now the widely accepted term. 5   6 It is commonly, but not always associated with acute hypertension and is now increasingly being diagnosed, because of increased availability and improvement of brain imaging techniques. 7

PRES can be considered to be the basis of the neurological manifestations of preeclampsia/eclampsia. 8 Cases can present in very early pregnancy (before the 20th week of gestation), as well as rarely in the late stages of pregnancy with intrauterine death. 9 Severe pre-eclampsia (defined as arterial blood pressure >170/110 mm Hg) is common in most women, but rare cases of PRES in pregnant women with normal blood pressure and without pre-eclampsia have also been described. 10 The major clinical conditions associated with PRES are represented in box 1 .

Immunosuppressive/cytotoxic drugs.

Hypertensive encephalopathy.

Pre-eclampsia/eclampsia/HELLP syndrome.

Autoimmune disorders, for example, SLE.

Acute or chronic renal diseases.

High dose steroids.

Liver failure/transplantation.

Endocrine dysfunction.

Hypercalcemia/hyperparathyroidism.

Bone marrow transplant.

Massive blood transfusion.

Porphyrias.

PRES, posterior reversible encephalopathy syndrome; SLE, systemic lupus erythematosus; HELLP, Hemolysis, Elevated Liver Enzymes and Low Platelet count; HUS/TTP, Hemolytic Uraemic Syndrome/ Thrombotic Thrombocytopenic Purpura.

Pathophysiology

The exact pathophysiology of PRES has not been completely explained, but hypertension and endothelial injury seem to be almost always present. Vasoconstriction resulting in vasogenic and cytotoxic oedema is suspected to be responsible for the clinical symptoms and the neuroradiological presentation. 11 Barring cerebral ischaemia or haemorrhage which can result in permanent damage, PRES is usually reversible. 1 Hypertension is the most common precipitating factor, with endothelial dysfunction playing an important role. 12 The various mechanisms explaining the pathophysiology of PRES include (i) failure of cerebral autoregulation causing vasogenic oedema, (ii) cerebral vasoconstriction and (iii) disruption of the blood brain barrier due to endothelial disruption. 5 Among the various theories that have been proposed for PRES, failure of brain autoregulation causing vasogenic oedema is presently the most accepted one.

Once the cerebral autoregulation, which maintains a constant blood flow to the brain despite alterations in the systemic pressures gets disrupted, increased, perfusion pressure causes extravasation of fluid by overcoming the blood brain barrier. 13–15 This can be briefly explained as follows. Cerebral blood flow is usually regulated by dilatation and constriction of vessels to maintain adequate tissue perfusion 15 which also avoids excessive increase in the intracerebral pressure. Sustained mean arterial pressure more than 150–160 mm Hg results in the breakdown of autoregulation mechanisms leading to hyperperfusion and cerebral vessel damage, resulting in interstitial extravasation of proteins and fluid, causing vasogenic oedema. Above 200 mm Hg mean arterial pressure (MAP), the changes start to become irreversible. 15 Chronic hypertension and atherosclerosis, which usually accompany PRES, are known to reduce the effectiveness of autoregulation. 16

Although this theory explains why control of hypertension benefits these patients, it does not explain few things such as the occurrence of PRES in the absence of hypertension and the correlation of extent of the oedema and the severity of hypertension. Also, some positron-emission tomography based studies have actually demonstrated cerebral hypoperfusion instead of hyperperfusion. 7   14–17

Another theory has implicated a systemic inflammatory state causing endothelial dysfunction as the cause of PRES. 15 Systemic inflammatory process such as sepsis, eclampsia, transplantation and autoimmune disease are usually associated with PRES, which can lead to reversible focal and diffuse abnormalities seen on angiographic studies. Vasoconstriction that occurs during cerebral autoregulation has a propensity to worsen pre-existing inflammatory endothelial dysfunction. This leads to further hypoxia and subsequent vasogenic oedema. 15 Although this theory explains well the role of endothelial dysfunction due to inflammation, it still does not explain the occurrence of PRES in the absence of inflammation. 16   17

A simplified flowchart describing the pathogenesis of PRES has been shown in figure 1 .

The pathogenesis of PRES. 6   18   19 PRES, posterior reversible encephalopathy syndrome.

Breakdown of the blood brain barrier and endothelial dysfunction occurs in PRES with fluid and macromolecule extravasation into the interstitium. Increased concentrations of circulating cytokines (eg, tumour necrosis factor α, interleukin 1 and endothelin 1) activate endothelial cells and allow interaction and adhesion of circulating leucocytes( figure 2 ). The tight junctions are disrupted and vascular endothelial growth factor expression is increased, leading to increased vascular permeability and vasogenic oedema.

A representational diagram showing the pathophysiology of PRES. PRES, posterior reversible encephalopathy syndrome.

To complicate the matter further, not all the patients with PRES have hypertension, and cytotoxicity is thought to be the mechanism underlying cerebral oedema in these patients. The associated conditions include cytotoxic therapies (eg, ciclosporin, tacrolimus), infection/sepsis/shock, autoimmune disease and exposure to toxic agents. 6   18   19 The mechanism might be direct toxicity to vascular endothelium leading to capillary leakage and breakdown of the blood brain barrier, which triggers vasogenic oedema. 2 The damage may also be seen with non-toxic levels of these drugs.

Severe anaemia can be a predisposing factor for PRES due to the endothelial dysfunction caused by insufficient oxygen supply. This can further damage and disrupt the blood brain barrier. 20 Rapid blood transfusion in these patients may cause a rapid increase in total blood volume, with resultant cerebral blood flow overload. This acute cerebral hyperperfusion disrupts cerebral autoregulation and might result in the vasogenic oedema found in PRES. 5

Clinical presentation

The symptoms of PRES are variable, ranging from visual disturbances which may present as blurred vision, homonymous hemianopsia and cortical blindness, to altered consciousness presenting as mild confusion, agitation or coma. Other symptoms may include nausea, vomiting and seizures. Status epilepticus is common, which may be generalised. Non-convulsive status can be prolonged and last for days in PRES and should be carefully observed. Drug intoxication and psychosis should be ruled out in these cases, so that treatment can initiated as early as possible. 5

The most common symptoms seen in obstetric patients are seizures (45%), visual disturbances (34%), alteration of consciousness (19%) 1 and focal deficits (4%). 21 The degree of hypertension is not associated with the extent of cerebral lesions and oedema can also occur at lower levels of arterial blood pressure. This is chiefly due to ongoing endothelium damage, as indicated by the high lactic acid dehydrogenase (LDH) levels in laboratory tests. 22   23

Imaging studies

The most common location of the lesions in PRES is the parietal-occipital lobe or ‘posterior’ area of the brain. Lesions may also be observed in the anterior regions, basal ganglia, brainstem and the cerebellum. 1   24   25 The characteristic imaging patterns in PRES are represented in box 2 . 26 Symmetrical white matter abnormalities suggestive of oedema may be seen in the CT and MRI scans, but not exclusively in the posterior parieto-occipital regions of the cerebral hemispheres. 1   27   28

Holo-hemispheric watershed.

Superior frontal sulcus.

Dominant parietal/occipital.

Partial and/or asymmetric PRES.

PRES, posterior reversible encephalopathy syndrome.

Diffusion-weighted imaging is essential to distinguish between vasogenic and cytotoxic oedema. 1   29 Diffusion-weighted MRI is the modality of choice for confirming the diagnosis of PRES( figure 3 ) and to differentiate between reversible vasogenic and irreversible cytotoxic oedema, as compared with a CT scan, which can be normal in some cases of PRES. Radiologically detectable cerebral lesions may persist in some cases in spite of intensive monitoring and prompt aggressive therapy. 1

MRI with T2-flair-weighted images showing the typically hyperintense bilateral lesions indicating vasogenic oedema in the parieto-occipital regions as well as less common lesions in the frontal regions and brain stem (arrows). 27   28

The key thing to remember in the management of PRES is early diagnosis and initiation of therapy. Many patients may require intensive care unit (ICU) care for aggressive management of their symptoms such as seizures, encephalopathy and status epilepticus. 30 The important points of therapy include: 31

Prompt induction of labour in cases of pre-eclampsia/eclampsia and HELLP.

Immediate removal of the offending cytotoxic drugs/immunosuppressants.

Stabilisation of the patient with adequate hydration, along with correction of acidosis and electrolyte abnormalities, if any.

Gradual reduction of blood pressure in patients with hypertension to avoid sudden hypoperfusion of vital organs.

Prevention and management of seizures in pregnant women by magnesium sulfate. For seizures in non-pregnant patients presenting with PRES, first-line drugs used are diazepam, phenobarbital and fosphenytoin. Refractory cases can be started on propofol or midazolam.

Dialysis for patients presenting with renal failure.

Airway management and intubation in altered patients with a poor Glasgow Coma Score, as per the standard protocol.

PRES in non-obstetric cases

In cases of PRES caused by factors other than pre-eclampsia and eclampsia, the most effective therapy includes withdrawal of the offending agent, immediate control of blood pressure, anticonvulsive therapy and temporary renal replacement therapy (haemodialysis/peritoneal dialysis) if required. Aggressive treatment with corticosteroids and cyclophosphamide is effective in cases of SLE-related PRES. 5

PRES in pre-eclampsia/eclampsia

The majority of obstetric cases with pre-eclampsia and eclampsia are treated with a similar protocol. Initially, the mother needs to be stabilised by means of antihypertensive and antiepileptic drugs, especially labetalol, nifedipine and magnesium sulfate. 32 The underlying cause has to be removed without delay, and a caesarean section has to be performed to reduce feto-maternal stress. General anaesthesia is preferred if there are complications such as coagulopathy, seizures or thrombocytopenia. Neuroaxial anaesthesia should always be given for the majority of patients without any complications as due to the antihypertensive effect of sympathetic blockade, it is the least risky for the mother and fetus. Rapid reduction of blood pressure by more than 15%–25% should be avoided as it can worsen the cytotoxic oedema and compromise uteroplacental perfusion. 1 Magnesium sulfate can prevent convulsions and reduce cerebral oedema. 33 The use of thiopental, valproate or phenytoin has been reported only for status epilepticus in these patients. 34 Specific cerebral antioedema therapy with steroids or mannitol has not been found to be superior to magnesium sulfate in achieving neurological recovery. 35

A concise overview of the management of PRES has been described in figure 4 .

Management of PRES. PRES, posterior reversible encephalopathy syndrome.

Prognosis and outcomes

PRES usually has a favourable prognosis among pregnant women, with resolution being rapid and complete after adequate therapy. 36 Permanent damage can persist in a few cases (6%) and death due to haemorrhage has been described in a couple of patients. 37–39 ICU care is advisable for postcaesarean patients to allow monitoring and sufficient recovery. 1 Recurrence of PRES is not uncommon in patients presenting with repeated episodes/flares of hypertensive crisis, renal failure, autoimmune conditions and multiorgan failure. 31

Although prognosis is good for most patients, delayed diagnosis and treatment may lead to mortality or irreversible neurological deficits. Poor prognosis is associated with factors such as severe encephalopathy, chronic hypertension, neoplastic aetiology, delayed diagnosis of causative factor, multiple comorbidities, elevated C-reactive protein (CRP) and coagulopathy. 40   41 Involvement of the corpus callosum, extensive cerebral oedema or haemorrhage, restrictive diffusion and subarachnoid haemorrhage are the MRI features which predict a worse prognosis. 42–44

PRES has been increasingly recognised in recent years and has been the cause of recurrent physician consultations for obstetric pre-eclamptic and eclamptic cases. In majority of patients, persistently elevated blood pressures remain the chief culprit for the clinical symptoms as well as the neurological deficits. Early diagnosis by diffusion weighted MRI scans, and differentiation from other causes of altered sensorium, that is, seizures, meningitis and psychosis, is extremely important to initiate treatment and prevent further complications. Reduction of blood pressure and seizure control remain the mainstays of therapy after prompt stabilisation of the patient and removal of any known toxic insult. Although most cases resolve successfully and carry a favourable prognosis, patients with inadequate therapeutic support or delay in treatment may not project a positive outcome.

Posterior reversible encephalopathy syndrome is increasingly being recognised now due to better imaging techniques.

Pathophysiology not completely elucidated, but hypertension, vasoconstriction and endothelial dysfunction seen to be important inciting factors.

Management protocols need to be specific and well defined, especially in obstetric cases.

Can posterior reversible encephalopathy syndrome (PRES) be predicted from early signs and symptoms in high-risk cases?

What is the pathophysiology of PRES?

Do early intervention, treatment and intensive care unit care have any effect on the prognosis of patients with PRES?

Poma S, Delmonte MP, Gigliuto C et al . Management of posterior reversible syndrome in preeclamptic women. Case Rep Obstet Gynecol 2014;2014:928079. https://doi.org/10.1155/2014/928079 . (Ref. 1)

Sudulagunta SR, Sodalagunta MB, Kumbhat M, Nataraju AS. Posterior reversible encephalopathy syndrome (PRES). Oxf Med Case Rep 2017;2017(4):omx011. doi: 10.1093/omcr/omx011 . (Ref. 5)

Bartynski W. Posterior reversible encephalopathy syndrome, part 2: controversies surrounding pathophysiology of vasogenic oedema. Am J Neuroradiol 2008;29:1043–9. (Ref. 16)

Fugate JE, Rabinstein AA. Posterior reversible encephalopathy syndrome: clinical and radiological manifestations, pathophysiology, and outstanding questions. Lancet Neurol 2015;14:914–25. (Ref. 19)

Hinduja A, Habetz K, Raina SK, Fitzgerald RT. Predictors of intensive care unit utilisation in patients with posterior reversible encephalopathy syndrome. Acta Neurol Belg 2017;117:201–6. doi: 10.1007/s13760-016-0703-5. (Ref. 31)

Hinduja A. Posterior reversible encephalopathy syndrome: clinical features and outcome. Front Neurol 2020;11:71. doi: 10.3389/fneur.2020.00071. (Ref. 32)

AP did the research and final submission. RJ reviewed and edited the manuscript.

The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

None declared.

Not required.

Not commissioned; externally peer reviewed.

Poma   S , Delmonte   MP , Gigliuto   C , et al.    Management of posterior reversible syndrome in preeclamptic women . Case Rep Obstet Gynecol   2014 ; 2014 : 1 – 6 . doi:10.1155/2014/928079

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OTHER VASCULAR DISORDERS

Posterior Reversible Encephalopathy Syndrome (PRES)

• clinical-radiologic syndrome
• sometimes called reversible posterior leukoencephalopathy syndrome ( RPLS) or acute hypertensive encephalopathy
• pathologic changes may extend beyond the posterior regions
• some patients may develop permanent brain damage with neurological deficits
• diagnosis is based on imaging methods (mainly typical MRI findings on T2 and FLAIR)

Pathophysiology of PRES

• decompensated hypertension (~ BP > 170-190 mm Hg) impairs cerebral autoregulation , leading to vasodilatation, endothelial dysfunction, and subsequent vasogenic edema
• reactive vasoconstriction is followed by hypoperfusion  [Bartynski, 2008]
• a systemic inflammatory response with endothelial dysfunction (a theory supported by the association with sepsis, pre-eclampsia, and autoimmune diseases), where released vasoactive substances increase vascular permeability (⇒ edema). In these patients, PRES may occur even with normal BP ! [Kurukumbi, 2013]
• changes are generally reversible with early therapy; prolonged duration may lead to ischemia or hemorrhage
• lesions are typically localized in the parietal and occipital lobes (but may also occur in the frontal and temporal lobes, cerebellum, and basal ganglia) [Legriel, 2011]

Clinical presentation

• moderate-to-severe intensity
• often showing poor response to analgesics
• nausea, vomiting
• encephalopathy with delirium/quantitative disturbances of consciousness (ranging from somnolence to coma) – exclude NCSE!
• epileptic seizures (in up to 90% of cases, status epilepticus occurring in ~ 3% of cases)
• hallucinations
• cortical blindness, which may be associated with its denial ( Anton-Babinski syndrome )
• hemianopsia

• vertigo, ataxia, etc.
• no correlation has been observed between mean BP and severity of radiologic changes
• hypertensive crisis may precede neurologic signs by ≥ 24 h

Diagnostic evaluation

Computed tomography (ct).

Magnetic resonance imaging (MRI)

• DDx of acute ischemia (with a hypointense lesion in ADC map)
• DWI may exhibit T2 shine-through
• T1 – hypointense
• lesions can also be found in watershed areas of the frontal and temporal lobes, in the cerebellum, basal ganglia, and thalamus [Raman, 2017]
• changes are observed in both cortical and subcortical regions.
• T1C+ –   variable enhancement is seen in ~30% of patients
• GRE can effectively detect microbleeds
• a combination of PRES and acute ischemia is reported in ~ 10-25% of cases

• MRA may reveal a vasculopathic pattern with focal vasoconstrictions/vasodilatation (which may cause difficulty in DDx of vasculitis)

Other diagnostic methods

• lumbar puncture
• blood tests (e.g., autoantibodies, Ca 2+ /S, Mg 2 +/S, etc.)
• brain biopsy if an infiltrative process is suspected

Differential diagnosis

• compared to ischemia, the foci in PRES appear hyperintense on the ADC map
• ischemia or hemorrhage may develop as complications of PRES
• severe hypoglycemia
• acute posterior circulation stroke
• progressive multifocal leukoencephalopathy (PML)
• sinus thrombosis
• gliomatosis cerebri
• hypoxic-ischemic encephalopathy
• SMART syndrome (stroke-like migraine attacks after radiotherapy)
• inflammatory cerebral amyloid angiopathy

→ DDx of leukoencephalopathies see here

• with early treatment, the prognosis is good
• prolonged duration may lead to irreversible neurological deficits

Elimination of the cause of PRES

• stabilize and maintain blood pressure within a target range; prevent significant fluctuations
• identify and discontinue toxic drugs
• induce delivery in case of eclampsia
• correct underlying metabolic disorders

Symptomatic therapy

• the goal is to reduce mean arterial pressure (MAP) by 20-25% in the first 1-2 hour(s)
• preferably use IV  urapidil or labetalol
• long-term antiseizure medication is usually unnecessary
• correct potential hypomagnesemia
• corticosteroids may theoretically improve edema, but there is no hard evidence of their efficacy
• most patients improve within 12-24 hours (up to several days) with prompt treatment
• MRI findings may persist for weeks
• delayed treatment can lead to serious complications (ischemic stroke/bleeding) with permanent disability
• death is usually caused by hemorrhage or massive edema in the posterior cranial fossa

What is Posterior Reversible Encephalopathy Syndrome (PRES)?

• PRES is a neurological disorder characterized by variable symptoms such as headaches, seizures, altered mental status, and visual disturbances, caused by vasogenic edema predominantly in the posterior regions of the brain

What causes PRES?

• PRES is often associated with acute hypertension, renal disease, autoimmune disorders, and the use of certain immunosuppressive or chemotherapeutic agents

How is PRES diagnosed?

• diagnosis is primarily based on clinical presentation and characteristic findings on neuroimaging , particularly magnetic resonance imaging (MRI) showing edema in the posterior regions of the cerebral cortex

Is PRES truly reversible?

• in most cases, PRES is reversible with appropriate management of the underlying cause and supportive care
• however, delays in diagnosis or treatment, severe or prolonged episodes, and certain underlying conditions can lead to irreversible brain damage or other complications

What is the treatment for PRES?

• treatment focuses on managing the underlying cause, such as controlling blood pressure, discontinuing offending drugs, and treating autoimmune diseases or renal dysfunction
• supportive care for symptoms like seizures is also important

How common is PRES?

• PRES is a rare condition, but its exact prevalence is unknown. It is more commonly reported in patients with acute medical conditions and those receiving specific treatments that affect blood pressure or immune functions

Can PRES be prevented?

• prevention focuses on managing risk factors, such as controlling blood pressure, monitoring renal function, and carefully using medications associated with PRES.

More results...

GENERAL MANAGEMENT OF STROKE

Early management of patients with suspected stroke

General management of acute stroke patients

Prevention of venous thromboembolism (VTE) in stroke patients

Arterial hypertension

Blood pressure management in an acute stroke

Hypertensive crisis

Intracranial hypertension

Rostrocaudal deterioration

Management of intracranial hypertension

Acute symptomatic seizures (ASS)

2HELPS2B score

Consequences of stroke

Overview of clinical consequences of stroke

Poststroke spasticity

Poststroke depression

Vascular cognitive impairment (VCI)

Stroke-related epilepsy

ISCHEMIC STROKE

Evaluation of an acute ischemic stroke

Transient ischemic attack (TIA)

ABCD 2 score

Stroke mimics

Transient global amnesia (TGA)

Stroke and migraine

Benign paroxysmal positional vertigo (BPPV)

Vestibular neuritis

Acute stroke therapy

Ischemic penumbra

Recanalization therapy in acute stroke

Intravenous thrombolysis in acute stroke

Contraindications to intravenous thrombolysis

Protocols for thrombolytic therapy

Fibrinolytic drugs

Mechanical recanalization in acute stroke

Angiographic grading of cerebral revascularization

Unfavorable vascular anatomy during endovascular treatment

Complications of endovascular procedures

Intra-arterial thrombolysis

Sonothrombolysis

Recanalization therapy in anticoagulated patients

Recanalization therapy in pediatric stroke

Surgical treatment of an acute ischemic stroke

Antiplatelet and anticoagulant therapy in acute stroke

Acute stroke in an anticoagulated patient

Complications

Overview of acute stroke complications

Malignant cerebral infarction

Topical diagnosis of stroke

Vertebrobasilar stroke

Vertebrobasilar steno-occlusive disease

Stroke etiology

Etiologic classification of ischemic stroke

TOAST classification of stroke

Chinese Ischemic Stroke Subclassification (CISS)

SSS-TOAST classification

Bamford/Oxford classification

Large artery atherosclerosis

Aortic arch atherosclerosis

Assessment and classification of atherosclerotic plaques

Cholesterol Embolization Syndrome

Cardioembolic stroke

Small vessel disease

Lacunar stroke

Capsular warning syndrome (CWS)

Binswanger’s disease

Overview of Genetic Small Vessel Diseases

Vasculopathies

Arterial dissection

Aortic dissection

Fibromuscular dysplasia (FMD)

Moyamoya disease

Carotid artery web

Radiation-induced vasculopathy

Reversible Cerebral Vasoconstriction Syndrome (RCVS)

Focal cerebral arteriopathy (FCA)

Smooth Muscle Alpha-Actin (ACTA2) angiopathy

Grange syndrome

Heritable connective tissue disorders (HCTDs)

Marfan syndrome

Ehlers-Danlos syndrome

Noninflammatory microangiopathies

MELAS (mitochondrial encephalopathy)

Fabry disease

Vasculitis – overview

Primary angiitis of CNS (PACNS)

Takayasu arteritis

Temporal (giant cell) arteritis

Granulomatosis with polyangiitis (GPA) ( Wegener)

Polyarteritis nodosa (PAN)

Systemic lupus erythematosus (SLE)

Thromboangiitis obliterans (Buerger´s disease)

Susac syndrome

Behçet disease

Neurosarcoidosis

Varicella zoster virus vasculopathy

Neuroborreliosis and stroke

Hematologic disorders associated with ischemic stroke

Inherited thrombophilia and ischemic stroke

Antiphospholipid syndrome (APS)

Sickle cell disease (SCD)

Hyperviscosity syndrome

Heparin-induced thrombocytopenia (HIT)

Thrombotic thrombocytopenic purpura (TTP)

Cancer-related stroke

Dolichoectasia

Idiopathic inflammatory bowel diseases

Stroke and celiac disease

Pulmonary AV malformation (PAVM)

Neurological complications during extracorporeal circulation

Stroke and HIV infection

Cryptogenic stroke

Stroke in young adults

Prevention and treatment of ischemic stroke in pregnancy

Stroke prevention

Prevention of ischemic stroke

Vascular risk factors – overview

ASCVD risk estimator

Diabetes mellitus

Dyslipidemia

Familial hypercholesterolemia (FH)

Lipid-lowering therapy

Statins and their interactions

Antiinflammatory drugs

Other vascular risk factors

Preventive procedures

Carotid endarterectomy (CEA)

Carotid angioplasty and stenting (CAS)

Management of asymptomatic carotid stenosis

Patent foramen ovale (PFO)

Left Atrial Appendage Occlusion (LAAO)

Management of intracranial stenosis

Extracranial-intracranial bypass

INTRACEREBRAL HEMORRHAGE

Etiology and clinical presentation of intracerebral hemorrhage

Cerebral Microbleeds (CMB)

Intraventricular hemorrhage in adults

Cerebral amyloid angiopathy (CAA)

Cerebral amyloid angiopathy-related inflammation (CAA-RI)

Hemorrhagic Complications in Acute Ischemic Stroke

Malformations

Cerebral arteriovenous malformation (AVM

Carotid-cavernous fistula (CCF)

Dural arteriovenous fistula (DAVF)

Venous angioma (DVA)

Cerebral cavernous malformation

Capillary telangiectasia

Diagnosis of intracerebral hemorrhage

Black Hole Sign

Max-ICH score

Intracerebral hemorrhage scales and scores

Management of intracerebral hemorrhage

Risk and prevention of bleeding in anticoagulant therapy

CEREBRAL VENOUS SINUS THROMBOSIS

Clinical presentation and etiology of cerebral venous thrombosis

Diagnosis of cerebral venous thrombosis

Management of cerebral venous sinus thrombosis – overview

General therapy and acute anticoagulation in cerebral venous thrombosis

Endovascular and surgical treatment of cerebral venous thrombosis

Management in the subacute phase of cerebral venous thrombosis

Cerebral venous thrombosis and pregnancy

Anatomy of cerebral veins and dural sinuses

SUBARACHNOID HEMORRHAGE

Definition and etiology of subarachnoid hemorrhage

Clinical presentation and complications of subarachnoid hemorrhage

Subarachnoid hemorrhage scales

Diagnosis of subarachnoid hemorrhage

Brain aneurysm diagnosis

Management of subarachnoid hemorrhage

Endovascular treatment of cerebral aneurysm

Vasospasms in subarachnoid hemorrhage

TCD/TCCD vasospasm monitoring

Superficial siderosis

Nontraumatic convexal subarachnoid hemorrhage

Management of asymptomatic intracranial aneurysm

Specifics of SAH treatment during pregnancy

NEUROIMAGING

Overview of imaging modalities for an acute stroke

Computed tomography

Computed tomography (CT) in stroke diagnosis

ASPECT score

CT angiography CT perfusion (CTP)

Magnetic resonance imaging

Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging Contraindications

MR-DWI in the acute stroke diagnosis

Gadolinium-based contrast agents (GBCAs)

Neurosonology

Neurosonology – overview

Hemodynamics Notes

Physical principles of ultrasound

Extracranial Doppler Sonography

Subclavian (vertebral) steal syndrome

Bow Hunter´s syndrome

Intima-media thickness (IMT)

Transcranial ultrasound (TCD/TCCD)

Transcranial ultrasound monitoring

Vasospasm Monitoring

Neurosonology and the brain death diagnosis

TCD/TCCD bubble test

Thrombolysis in Brain Ischemia (TIBI)

Cerebral vasomotor reactivity (CVR) assessment

Neurosonology in intensive care

Optic nerve sheath ultrasound (ONSUS)

Digital subtraction angiography (DSA)

Indications and technique

Balloon Test Occlusion (BTO)

Neuroimaging in pediatric stroke

Neuroimaging during pregnancy and lactation

Administration of iodinated contrast agents

Contrast-induced encephalopathy (CIE)

Collateral circulation assessment

Carotid artery occlusion

Lumbar puncture and antithrombotic therapy

Antiplatelet therapy

Antiplatelet drugs

Resistance to antiplatelet drugs

Antiplatelet therapy in stroke prevention

Perioperative and Periprocedural Management of Antiplatelet Therapy

Vascular risk factors therapy

Lipid-lowering therapy – overview

Statin intolerance

Bempedoic acid

Inclisiran (Leqvio)

Anticoagulant therapy

Timing of anticoagulant therapy

Perioperative and Periprocedural Management of Anticoagulant Therapy

Acute stroke in the anticoagulated patient

Switching of antithrombotic therapy

Neutralization of the anticoagulant effects

Andexanet alfa

Idarucizumab (PRAXBIND)

Anticoagulant drugs

Unfractionated Heparin (UFH)

Low Molecular Weight Heparins (LMWHs)

Fondaparinux

Direct Oral Anticoagulants (DOACs)

Dabigatran (PRADAXA)

Apixaban (ELIQUIS)

Rivaroxaban (XARELTO)

Edoxaban (LIXIANA)

Reduced-dose DOACs

Scales and scores

Barthel index

Carotid artery risk (CAR) score

Modified Rankin Scale (mRS)

NIH Stroke Scale (NIHSS)

Risk of Paradoxical Embolism (RoPE) Score

AF-ROPE Score

CHA 2 DS 2 -VASc score

FAZEKAS scale

The ARWMC Rating Scale

HAT score – prediction of post-tPA hemorrhage

SSS-TOAST classification of stroke

Clot Burden Score (CBS)

RASS (Richmond Agitation-Sedation Scale)

Glasgow Coma Scale (GCS)

Muscle strength testing (Oxford scale)

Anatomy and physiology

Anatomy of cerebral arteries

Anatomical variants of cerebral arteries

Arterial territories

Blood Supply of the Spinal Cord

Collateral cerebral circulation

Regulation of cerebral blood flow

Subarachnoid (basal) cisterns

General neurology chapters

Basic neurological examination

Signs and symptoms of cerebral lesions

Brainstem syndromes

Parinaud syndrome

Internuclear ophthalmoplegia (INO)

Bulbar and pseudobulbar palsy

Relative afferent pupillary defect (RAPD)

Disorders of consciousness

Topical evaluation and etiology of consciousness disorders

Pupillary response in consciousness disorders

Specific consciousness disorders

Brain death diagnosis

Brainstem reflexes

TCD/TCCD and the brain death diagnosis

Papilledema

Differential diagnosis of visual impairment

Pseudotumor cerebri

Raeder paratrigeminal syndrome

Other vascular disorders

Ocular vascular syndromes

Transient monocular vision loss

Ischemic optic neuropathy (ION)

Central retinal artery occlusion (CRAO)

Retinal vein occlusion (RVO)

Spinal cord vascular disorders

RCVS 2 score

Cerebral hyperperfusion syndrome (CHS)

Thoracic Outlet Syndrome (TOS)

Drop attack

Carotid Body Tumor

Sturge-Weber syndrome

POSTERIOR REVERSIBLE ENCEPHALOPATHY SYNDROME (PRES)

American Journal of Neuroradiology

Advanced Search

Posterior Reversible Encephalopathy Syndrome (PRES)

• Posterior reversible encephalopathy syndrome (PRES) is a noninflammatory cerebral vasculopathy due to cerebrovascular autoregulatory disorder or an endothelial dysfunction, usually related to a severe and quick rise of arterial blood pressure.
• Studies have also demonstrated association with specific drugs (e.g., Tacrolimus) and diseases (e.g., systemic lupus erythematous), even in the absence of hypertension.
• Associated with headaches, seizures, impaired consciousness, and visual disturbances
• Reversible cortico-subcortical hyperintensities on FLAIR/T2WI, usually without water restriction (vasogenic edema); commonly affects watershed zones of the parietal and occipital lobes (typical presentation) after episodes of high blood pressure
• Atypical PRES is characterized by similar lesions affecting the basal ganglia and frontal lobe and/or brainstem and cerebellum.
• After gaining control of the precipitating cause, lesions usually evolve to complete resolution. Rare cases may lead to permanent damage, usually caused by cortical/subcortical hemorrhagic foci.
• CNS vasculitis (including SLE): May be very difficult to differentiate from PRES, especially on the first studies; more likely to cause water diffusion restriction and permanent lesions than PRES. Lesions usually do not respond to arterial pressure control. The most specific imaging finding is vessel thickening and enhancement on post-contrast high-resolution T1WI, preferably with 3T MRI, to increase the relatively low sensitivity of vasculitis findings on MRA.
• Hypoglycemia: More likely to show restriction on DWI; usually spares cerebellum; always associated with low serum glucose levels (less than 50 mg/dL) of any etiology; reversibility depends of the duration and severity of hypoglycemia; extensive basal ganglia T2/FLAIR hyperintensities related to worse prognosis
• Cerebellar stroke: Acute cerebellar symptoms associated with FLAIR/T2 hyperintensities, with marked restriction on DWI, usually unilateral, respecting vascular territories; absence of rapid improvement with pressure control
• Blood pressure control
• Treatment of the precipitating cause

A 29-year-old woman with irregular adherence to treatment for lupus erythematosus nephritis; presents with nausea, headaches, and hypertension that were relieved by hemodialysis; shown: admission MRI (A and B) and follow-up MRI (C) a few days after hemodialysis

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• Posterior reversible encephalopathy syndrome
• 1 Background
• 2 Clinical Features [3]
• 3.1 Seizure
• 4 Evaluation
• 5 Management
• 6 Disposition
• 8 References
• Somewhat of a misnomer as changes seen on MRI are not limited to the posterior fossa and symptoms are not always reversible
• Renamed reversible posterior leukoencephalopathy syndrome (RPLS) by the American Academy of Neurology
• Risk factors: malignant hypertension , kidney disease, autoimmune disease, immunosuppression, eclampsia
• Hypertension-hyperperfusion: Hypertensive emergency causes vascular extravasation of fluid and vasogenic edema
• Endothelial dysfunction: Autoimmune or cytotoxic etiologies lead to endothelial dysfunction, leading to increased vascular permeability and edema
• Epidemiolgy: Most frequently in middle-aged females, which may be related to underlying disease [2]
• Prognosis: While many case reports suggest PRES is benign and fully reversible, the consequences of PRES, including intracerebral hemorrhage or extensive intracerebral edema, can result in residual neurologic deficits

Clinical Features [3]

• Onset may range from hours to days
• Seizures , including status epilepticus
• Encephalopathy , ranging from mild altered mental status to coma
• Visual disturbances
• Note that some proportion of patients may not exhibit significant hypertension; of note, a significant proportion of patients also had no known pre-existing hypertension [4]
• Headache , vomiting , or other focal neurological deficits

Differential Diagnosis [5]

• Hypertensive Encephalopathy
• Intracranial Hemorrhage
• Cerebral Venous Thrombosis
• Encephalitis
• Hepatic Encephalopathy
• Hyponatremia
• Psychiatric disorder
• First-time seizure
• Seizure with known seizure disorder
• Status epilepticus
• Temporal lobe epilepsy
• Non-compliance with anti-epileptic medications
• INH toxicity
• Brain abscess
• Intracranial hemorrhage
• Alcohol withdrawal
• Benzodiazepine withdrawal
• Barbiturate withdrawal
• Baclofen withdrawal
• Metabolic abnormalities: hyponatremia , hypernatremia , hypocalcemia , hypomagnesemia , hypoglycemia , hyperglycemia , hepatic failure , uremia
• Neurocysticercosis
• Impact seizure ( head trauma )
• Acute hydrocephalus
• Arteriovenous malformation
• Seizure with VP shunt
• Toxic ingestion (amphetamines, anticholinergics, cocaine, INH, organophosphates, TCA, salicylates, lithium, phenothiazines, bupropion, camphor, clozapine, cyclosporine, fluoroquinolones, imipenem, lead, lidocaine, metronidazole, synthetic cannabinoids, theophylline, Starfruit )
• Psychogenic nonepileptic seizure (pseudoseizure)
• Intracranial mass
• Hyperventilation syndrome
• Migraine headache
• Movement disorders
• Narcolepsy/cataplexy
• Post-hypoxic myoclonus ( Status myoclonicus )
• CT head to rule out other etiologies
• However, any brain region can be involved, including the frontal and temporal lobes
• Focus on altered mental status workup , with PRES as diagnosis of exclusion
• Consider lumbar puncture if there is a concern for meningitis or encephalitis
• May require EEG for detection of status epilepticus
• Treat the underlying etiology
• Control Blood Pressure , considering gradual reduction to avoid sudden hypoperfusion
• Discontinue immunosuppressants or cytotoxic medications
• Standard seizure management, if seizures are present
• In cases related to Preeclampsia or HELLP syndrome , consider early OB/GYN consultation for delivery [6]

Disposition

• Consider ICU for blood pressure titration, obtunded state, status epilepticus, intracranial hemorrhage, or other serious sequelae
• Hypertensive emergency
• ↑ Zelaya JE, Al-Khoury L. Posterior Reversible Encephalopathy Syndrome. [Updated 2022 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.
• ↑ Fischer M, Schmutzhard E. Posterior reversible encephalopathy syndrome. J Neurol. 2017 Aug;264(8):1608-1616. doi: 10.1007/s00415-016-8377-8. Epub 2017 Jan 4. PMID: 28054130; PMCID: PMC5533845.
• ↑ Staykov D. "Posterior reversible encephalopathy syndrome". PMID 21257628
• ↑ Fugate JE, Claassen DO, Cloft HJ, Kallmes DF, Kozak OS, Rabinstein AA. Posterior reversible encephalopathy syndrome: associated clinical and radiologic findings. Mayo Clin Proc. 2010 May;85(5):427-32. doi: 10.4065/mcp.2009.0590. PMID: 20435835; PMCID: PMC2861971.
• ↑ 5.0 5.1 Garg RK (January 2001). "Posterior leukoencephalopathy syndrome". Postgrad Med J 77 (903): 24–8. doi:10.1136/pmj.77.903.24. PMC 1741870. PMID 11123390
• ↑ Parasher A, Jhamb R. Posterior reversible encephalopathy syndrome (PRES): presentation, diagnosis and treatment. Postgrad Med J. 2020 Oct;96(1140):623-628. doi: 10.1136/postgradmedj-2020-137706. Epub 2020 May 28. PMID: 32467104.
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Posterior Reversible Encephalopathy Syndrome

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• 1 UC Riverside/Riverside Community Hosp.
• PMID: 32119379
• Bookshelf ID: NBK554492

Posterior reversible encephalopathy syndrome (PRES) is an illness in which a person can present with acutely altered mentation, drowsiness or sometimes stupor, visual impairment (e.g., visual hallucinations, cortical blindness, hemianopia, quadrantanopia, and diplopia), seizures (focal or general tonic-clonic), and sudden or constant, non-localized headaches. PRES can unfold acutely or subacutely, with symptoms developing within hours to days. Often, the presentation occurs in the context of acute uncontrolled hypertension, with systolic blood pressures ranging between 160 to 190 mmHg. The name designated to this clinical and radiographic syndrome is inspired from (1) radiographic findings of white matter edema (i.e., hyperintense T2 signal or hypointense T1 signal on magnetic resonance imaging (MRI)), typically found in the posterior cerebrum in a symmetric fashion (although asymmetric presentations are possible); and (2) the fact that symptoms are reversible, provided that the syndrome is recognized and treated promptly. However, the name used to describe the syndrome is misleading because the edema is not localized necessarily to the posterior cerebrum white matter and can appear in watershed zones other than parietal-occipital regions thalamus, and sometimes in the anterior circulation. Moreover, the syndrome is not always reversible. Some individuals can develop life-threatening complications, such as transforaminal cerebellar herniation and focal neurologic deficits, especially if prompt treatment is not initiated.

Copyright © 2024, StatPearls Publishing LLC.

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RELATED TOPICS

INTRODUCTION AND TERMINOLOGY

● Posterior reversible encephalopathy syndrome (PRES)

● Reversible posterior cerebral edema syndrome

● Posterior leukoencephalopathy syndrome

● Hyperperfusion encephalopathy

Diseases & Diagnoses

Issue Index

• Case Reports

Expert Opinion | April 2016

Posterior Reversible Encephalopathy Syndrome (PRES): A Case Report and Review of the Literature

Kevin G. Lazo, DO, Steven Mandel, MD, Bidyut Pramanik, MD, Jane Lee, MD, Maria V. Devita, MD, David Coven, MD, PhD, and Sandra Gelbard, MD

P osterior Reversible Encephalopathy Syndrome (PRES) is a condition caused by reversible subcortical vasogenic edema that can clinically manifest with headache, altered mental status, visual disturbances, and/or seizures. 1 Ahead we present a case of a woman who was admitted for intractable headaches and eventually found to have radiographic stigmata of PRES.

CASE REPORT

A 56-year old female presented with new onset blurry vision, diplopia, headache, and dizziness, 24 hours after being discharged from her local hospital. Her initial hospitalization was for hypertensive urgency with blood pressure as high as 230mmHg systolic, requiring administration of IV enalaprilat. Her symptoms of visual disturbance, headaches, and dizziness started shortly after discharge and worsened over the next 24 hours. Upon return to the emergency department, she was afebrile with a regular heart rate and rhythm. Systolic blood pressures ranged from 98-107mmHg, with diastolic blood pressure ranging from 54-67mmHg. The patient had no evidence of papilledema on fundoscopic examination, no focal neurologic deficits, and there was no observation of exophthalmos, ptosis, or nystagmus. Additionally, laboratory studies revealed ESR, TSH, and CRP all within normal limits.

She received 1-liter Bolus of Normal Saline, Benadryl 50mg PO once, and Reglan 10mg by mouth once. The Benadryl and Reglan were given for an initial diagnosis of migraine headache, which was subsequently relieved. A CT of the head without contrast was negative for intracranial hemorrhage. An MRI of the head with and without contrast was performed, and it demonstrated symmetric FLAIR/T2 signal abnormality predominately within the cortical and subcortical white matter of the occipital lobes bilaterally with corresponding restricted diffusion (Figure I). These findings were consistent with posterior reversible encephalopathy syndrome (PRES). The patient was discharged with a medication regimen to maintain her systolic blood pressure in a range between 120-140 mmHg, and with neuro-ophthalmology follow-up.

In 1996, Hinchey, et al. described a condition characterized by sudden headaches with or without neurologic deficits or seizures related to dysfunction of the autoregulatory properties of the cerebral vasculature. They coined the name, “reversible posterior leukoencephalopathy syndrome.” 1 In later years, the condition was renamed posterior reversible encephalopathy syndrome to more accurately consider that the stigmatic lesions are not restricted to white matter. 2 PRES is frequently associated with hypertension, sepsis, pre-eclampsia, eclampsia, autoimmune disorders (e.g. rheumatoid arthritis, Crohn’s disease, systemic lupus erythematosus), renal failure, hypomagnesemia, hypercalcemia, hypercholesterolemia, and exposure to immunosuppressive or cytotoxic medications. 3,4 Rarer associations may include iatrogenic causes such as the administration of linezolid, contrast, and intravenous immunoglobulin. Environmental insults such as inoculation of scorpion poison, intoxication with LSD, or an ephedra overdose are also implicated. 4

Figure 1. MRI: FLAIR and Diffusion Images

The exact mechanism of PRES is currently not well understood. One of the dominating hypotheses is that severe hypertension exceeds the auto-regulatory ability of the cerebral blood vessels, leading to compromise of the blood-brain barrier, and vasogenic edema. 3 The upper limit of auto-regulation of the cerebral vasculature is approximately 150-160mmHg. However this range can extend up to 30mmHg higher in acute sympathetic states. This phenomenon can occur because of the rich sympathetic innervation of the majority of the cerebral vasculature. However, because little sympathetic innervation exists in the posterior fossa, the parieto-occipital regions of the brain can be particularly susceptible to hyperperfusion. 4 Chronic hypertension may contribute to increased limits over time.

Despite PRES being associated with accelerated hypertension, approximately 15 to 20 percent of patients can be normotensive or hypotensive during initial evaluation, 5 as our patient presented. The existence of this finding suggests that the mechanism is not completely explained by defects in auto-regulation of the cerebral vasculature. Other postulated theories for PRES include physical disruption of the endothelial layer, blood-brain barrier compromise in inflammatory conditions such as sepsis or autoimmunity, or vessel abnormalities leading to cerebral vasoconstriction and hypo-perfusion states such as in eclampsia and cyclosporin toxicity. 5 Our patient may have been in a hypo-perfused state on presentation, likely stemming from the sudden changes in blood pressure from her prior hospitalization.

Clinically, PRES includes several types of clinical signs and symptoms. Approximately 50 to 80 percent of PRES patients are encephalopathic, 60 to 75 percent manifest with seizures, 50 percent with headaches, 33 percent with visual disturbances, 10 to 15 percent with focal neurologic deficits, and five to 15 percent with status epilepticus. 4 Encephalopathy in these patients can range from stupor to comatose. Seizures are often generalized, and may be multiple. Status epilepticus may also manifest, but this is less common. PRES can be a suspected reason for SE if the patient’s EEG is positive for parieto-occipital to temporal sharp waves. 6 The acute encephalopathy syndrome (confusion, headache, vomiting, and depressed consciousness) and visual disturbances (blurred, vision, hemianopsia, or complete cortical blindness) also may lead the clinician to place PRES in their differential diagnosis. Labs may reflect normal CSF, and laboratory signs of endothelin injury, such as increased LDH, thrombocytopenia, and the presence of schistocytes. 3

MRI is particularly useful in the diagnosis of PRES. Radiographic stigmata of the disease usually involves increased signal on T2 and fluid-attenuated inversion recovery (FLAIR) imaging of subcortical white matter with vasogenic edema predominantly involving the parieto-occipital and posterior temporal lobes of both hemispheres of the brain. 4 However, other structures such as the anterior cerebral regions, deep white matter, brainstem, and the cerebellum may also be involved. Three primary descriptive variations of radiographic findings exist in about 70 percent of patients: a dominant parieto-occipital pattern, holo-hemispheric watershed pattern, and superior frontal sulcus pattern. 7 Frontal and temporal lobe involvement can be seen in up to 75 percent of cases. Similarly, the edema can affect the basal ganglia and the brainstem in up to a third of cases and the cerebellum in up to half. 4 Finally, intracranial hemorrhage is common, complicating 10 to 25 percent of cases. Intra-parenchymal hemorrhage is the most common type of intracranial hemorrhage and subarachnoid hemorrhage is the second most common type. 8

When a patient presents with acute or subacute neurologic symptoms, the clinical context is important for the diagnosis of PRES. If a patient presents with neurologic symptoms as mentioned above, and is either in hypertensive emergency, has labile blood pressures, is on chemotherapeutics, has chronic hypertension, an autoimmune disorder, renal failure, or has pre-eclampsia/eclampsia PRES should be in the differential diagnosis. Other diseases to consider in the differential include infection, paraneoplastic encephalitis, malignancy, CNS vasculitides, alcohol withdrawal, drug intoxication, and acute stroke. 4 Appropriate workup should include a complete blood count, urine toxicology screen, lumbar puncture, and imaging - computed tomography without contrast (to rule out intracranial hemorrhage) and MRI without contrast (to evaluate for tumors or ischemic changes).

The general concept of PRES treatment should revolve around strict blood pressure control. To our knowledge, no randomized controlled trials have been performed to assess optimal therapeutic management for PRES. The general recommendation for those diagnosed with PRES is monitoring in an intensive care unit, because these patients can have labile blood pressures that would best be captured by monitoring with an arterial line. 4 Appropriate consultation services should be included depending on the suspected causative factor. 3 If applicable, the removal of any offending drugs or illicit substances, the treatment of seizures/SE, sepsis, or autoimmune disorder exacerbations, and consideration of delivery of the fetus by cesarean section in those with pre-eclampsia or eclampsia.

PRES patients who present with elevated blood pressure should be treated as hypertensive emergencies. Therefore it is recommended that blood pressure should be reduced by 25 percent within the first few hours of treatment. 4 Blood pressure control in the setting of hypertensive emergencies should be performed with intravenous medications that are short acting to achieve the pre-determined target blood pressure. First-line agents for PRES related hypertensive emergency include intravenous nicardipine (5-15mg/h) and labetalol (2-3mg/min). 12 Nitroglycerine is not recommended in PRES patients, as it has been suggested to aggravate the cerebral edema. 13 Table 1 displays a list of parenteral agents we are recommending in hypertensive emergency.

Patients usually fully recover within days to weeks. 9 More severe cases of PRES can result in residual permanent neurologic injury (hemiparesis, seizures, decreased visual changes) or death, typically from either intracranial hemorrhage, or brain herniation due to marked cerebral edema that causes dangerously high levels of global intracranial pressure. 10,11

PRES is a reversible condition presenting with acute neurologic symptoms ranging from headaches to seizures with radiographic evidence of vasogenic edema in various areas of the brain. Although the mechanism has not been fully elucidated, endothelial dysfunction/injury related to accelerated hypertension, exposure to certain medications, eclampsia, or autoimmune disorders have been implicated. Treatment of PRES revolves around strict blood pressure control using JNC guidelines for hypertensive emergencies, as well as correction of any potential causative factors. n

Kevin G. Lazo, DO is in the Department of Medicine, Northwell Health Lenox Hill Hospital in New York City.

Steven Mandel MD, PC is a Clinical Professor of Neurology at Lenox Hill Hospital, Hofstra Northwell School of Medicine.

Bidyut Pramanik, MD is Chief of Neuroradiology at Lenox Hill Hospital in New York City.

Jane A Lee, MD is a Neuroradiologist at Lenox Hill Hospital in New York City.

Maria V. DeVita MD, FACP, FASN is a Clinical Professor of Medicine at Hofstra Northwell School of Medicine in New York City, and Associate Director of the Division of Nephrology at Lenox Hill Hospital.

David L. Coven MD, PhD is the Director of the Cardiac Care Unit and an Interventional Cardiologist at the Northwell Health Lenox Hill Heart and Vascular Institute of New York.

Sandra Gelbard, MD is an Assistant Professor of Medicine at the NYU School of Medicine and the Hofstra Northwell School of Medicine.

1. Hinchey J, Chaves C, Appignani B, et al. A reversible posterior leukoencephalopathy syndrome. N Engl J Med. 1996;334:494-500.

2. Casey SO, Sampaio RC, et al. Posterior reversible encephalopathy syndrome: Utility of fluid-attenuated inversion recovery MR imaging in the detection of cortical and subcortical lesions. AJNR Am J Neuroradiol. 2000;21:1199-1206.

3. Staykov D, Schwab S. Posterior Reversible Encephalopathy Syndrome. Journal of Intensive Care Medicine. 2012;27(1):11-24.

4. Fugate JE, Rabinstein AA. Posterior reversible encephalopathy syndrome: clinical and radiologic manifestations, pathophysiology, and outstanding questions. Lancet Neurol 2015; 14: 914–25

5. Rabinstein AA, Mandrekar J, Merrell R, Kozak OS, Durosaro O, Fugate JE. Blood pressure fluctuations in posterior reversible encephalopathy syndrome. J Stroke Cerebrovasc Dis 2012; 21: 254–58.

6. Kozak OS, Wijdicks EF, Manno EM, Miley JT, Rabinstein AA. Status epilepticus as initial manifestation of posterior reversible encephalopathy syndrome. Neurology 2007; 69: 894–97.

7. Bartynski WS, Boardman JF. Distinct imaging patterns and lesion distribution in posterior reversible encephalopathy syndrome. AJNR Am J Neuroradiol 2007; 28: 1320–27.

8. Sharma A, Whitesell RT, Moran KJ. Imaging pattern of intracranial hemorrhage in the setting of posterior reversible encephalopathy syndrome. Neuroradiology 2010; 52: 855–63.

9. Roth C, Ferbert A. Posterior reversible encephalopathy syndrome: long-term follow-up. J Neurol Neurosurg Psychiatry 2010; 81: 773–77.

10. Grossbach AJ, Abel TJ, Hodis B, Wassef SN, Greenlee JD. Hypertensive posterior reversible encephalopathy syndrome causing posterior fossa edema and hydrocephalus. J Clin Neurosci 2014;21: 207–11.

11. Lee SY, Dinesh SK, Thomas J. Hypertension-induced reversible posterior leukoencephalopathy syndrome causing obstructive hydrocephalus. J Clin Neurosci 2008; 15: 457–59.

12. Servillo G, Bifulco F, De Robertis E, et al. Posterior reversible encephalopathy syndrome in intensive care medicine. Intensive Care Med. 2007;33(2):230-236.

13. Finsterer J, Schlager T, Kopsa W, Wild E. Nitroglycerin- aggravated pre-eclamptic posterior reversible encephalopathy syndrome (PRES). Neurology. 2003;61(5):715-716.

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Ultimovacs announces poster presentation at the 2024 american society of clinical oncology (asco) annual meeting.

NON-REGULATORY PRESS RELEASE

Oslo, June 1, 2024: Ultimovacs ASA (“Ultimovacs”) (OSE ULTI), a clinical-stage biotechnology company developing immunotherapeutic cancer vaccines, today announces that the data from the Phase II clinical trial INITIUM ( NCT04382664 ), will be presented in a poster session at the 2024 ASCO Annual Meeting, taking place May 31 – June 4, 2024, in Chicago, IL & Online. The late-breaking abstract can be found on the 2024 ASCO website: https://meetings.asco.org/abstracts-presentations/232936

INITIUM is an Ultimovacs-sponsored randomized, comparative, multicenter Phase II trial evaluating the company’s therapeutic cancer vaccine candidate UV1 in combination with the checkpoint inhibitors ipilimumab and nivolumab as first-line treatment in unresectable or metastatic malignant melanoma. The trial was conducted at 39 hospitals across the U.S., U.K., Belgium, and Norway, and enrolled 156 patients between June 2020 and July 2022.

The poster presentation features key findings and analyses after minimum 18-month follow up of the patients in the trial.

Presentation Details:

Abstract Number: LBA9519 Abstract Title: Ipilimumab and nivolumab plus UV1, an anticancer vaccination against telomerase, in advanced melanoma. Session Title: Poster Session – Melanoma/Skin Cancers Poster Board: 303 Date and Time: June 1, 2024, 1:30 PM – 4:30 PM (CT) Presenter: Paul Lorigan, Professor of Medical Oncology at the University of Manchester and Investigator in the INITIUM study

Following the presentation, the poster will be available online in the Investor section of the Company’s website: https://ultimovacs.com/

About Ultimovacs

Ultimovacs is a clinical-stage biotechnology leader in novel immunotherapeutic cancer vaccines with broad applicability. Ultimovacs’ lead cancer vaccine candidate UV1 is directed against human telomerase (hTERT) an antigen which is present in 85-90% of cancers in all stages of tumor growth. A broad clinical program, with Phase II trials in five cancer indications enrolling more than 670 patients, aims to demonstrate UV1’s impact in combination with other immunotherapies in multiple cancer types expressing telomerase and where patients have unmet medical needs. UV1 is universal, off-the-shelf and easy to use, and is a patented technology owned by Ultimovacs. In addition, Ultimovacs holds all rights of the proprietary TET technology platform for any possible future use of formulations in various solid tumor indications. The Company is listed on Euronext Oslo Stock Exchange (ULTI.OL).

For further information, please contact:

Carlos de Sousa, CEO Email: [email protected] Phone: +47 908 92507

Anne Worsøe, Head of Investor Relations Email: [email protected] Phone: +47 90686815

This stock exchange announcement was published by Anne Worsøe, Head of Investor Relations at Ultimovacs ASA, on June 1, 2024, at 14:15 CET.

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Posterior Reversible Encephalopathy Syndrome and Eclampsia: Pressing the Case for More Aggressive Blood Pressure Control

OBJECTIVE: To assess the prevalence, clinical presentations, and neuroimaging abnormalities in a series of patients treated for eclampsia at Mayo Clinic in Rochester, MN.

PATIENTS AND METHODS: We reviewed the records of all pregnant patients diagnosed as having eclampsia at Mayo Clinic in Rochester, MN, between January 1, 2001, and December 31, 2008. All patients who underwent neuroimaging were identified, and all studies were reviewed by an independent neuroradiologist. Comparisons were made between groups who did and did not undergo imaging to identify differentiating clinical or laboratory variables.

RESULTS: Thirteen cases of eclampsia were found, with neuroimaging studies available for 7: magnetic resonance imaging (n=6) and computed tomography (n=1). All 7 patients developed eclamptic seizures, and 2 of 7 patients had severe hypertension, with recorded systolic blood pressures exceeding 180 mm Hg. Neuroimaging showed characteristic changes of posterior reversible encephalopathy syndrome (PRES) in all patients. Follow-up imaging showed resolution in 2 of 3 patients; 1 patient had residual neuroimaging abnormalities.

CONCLUSION: Our results suggest that the clinical syndrome of eclampsia is associated with an anatomical substrate that is recognizable by neuroimaging as PRES. The levels of blood pressure elevation are lower than those reported in cases of PRES because of hypertensive encephalopathy. Further studies are needed to determine whether more aggressive blood pressure control and early neuroimaging may have a role in the management of these patients.

ADC = apparent diffusion coefficient; DBP = diastolic blood pressure; DWI = diffusion-weighted imaging; MRI = magnetic resonance imaging; PRES = posterior reversible encephalopathy syndrome; SBP = systolic blood pressure.

Preeclampsia is a pregnancy-specific disorder clinically characterized by hypertension (blood pressure ≥140/90 mm Hg) and proteinuria (≥300 mg in a 24-hour urine collection) occurring after 20 weeks of gestation in a previously normotensive patient. 1 Preeclampsia and its variants affect approximately 5% of pregnancies and remain leading causes of both maternal and fetal morbidity and mortality world-wide. 2 The incidence of progression to the convulsive form (ie, eclampsia) occurs in approximately 0.5% of patients with mild preeclampsia and 2% to 3% of those with severe preeclampsia, as defined by a systolic blood pressure (SBP) of 160 mm Hg or greater, a diastolic blood pressure (DBP) of 100 mm Hg or greater, nephrotic-range proteinuria (>3.5 g/24-hour urine), renal function impairment, thrombocytopenia, and/or evidence of microangiopathic hemolytic anemia, hepatocellular injury, pulmonary edema, and neurologic disturbances. 3 The incidence of eclampsia in developed countries averages 1 in 2000 to 3000 deliveries. 4 , 5 Seizure activity can manifest as 1 or more generalized convulsions with or without coma.

In 1992, Douglas and Redman 6 prospectively studied all cases of eclampsia in the United Kingdom. They identified 383 confirmed cases of eclampsia and described the occurrence of 1 or more of the following antecedent symptoms within hours before the onset of an eclamptic seizure: prodromal headache, visual disturbance (scotomata, amaurosis fugax, blurred vision, diplopia, homonymous hemianopsia), and epigastric pain. The relationship between the level of blood pressure and seizure onset, although considered relevant by most, remains controversial.

Posterior reversible encephalopathy syndrome (PRES) is a clinically recognizable entity that presents with neurologic signs and symptoms (headache, altered consciousness, visual abnormalities, and seizures) in conjunction with the unique neuroimaging findings of vasogenic edema involving the posterior circulation. An association between eclampsia and PRES was first described by Hinchey et al 7 in 1996. In this initial series, 3 of 15 patients with PRES had eclampsia, with other etiologies including hypertensive encephalopathy and immunosuppressive medications. Although this study established a clear association between eclampsia and PRES, few clinical studies followed to further document and support these associations. 8 - 10

Our study aimed to assess the prevalence and clinical presentation, along with the distribution and extent of neuroimaging abnormalities, among patients treated for eclampsia at Mayo Clinic in Rochester, MN, between 2001 and 2008. In addition, we reviewed their follow-up neuroimaging studies, when available, for evidence of persistent brain damage.

PATIENTS AND METHODS

With the approval of the Mayo Clinic Institutional Review Board, which waived the need for informed consent, we electronically reviewed the records of all obstetric patients seeking care at Mayo Clinic in Rochester, MN, between January 1, 2001, and December 31, 2008, for the diagnosis of eclampsia. Of these patients, 13 had a confirmed diagnosis of eclampsia based on International Classification of Diseases, Ninth Revision codes and the presence of previously published and widely accepted clinical criteria of hypertension, proteinuria, and seizure activity not attributable to other causes. 1 Findings for 3 of the patients had been previously reported. 11 Of the 13 patients, 7 patients had undergone neuroimaging subsequent to the diagnosis of eclampsia; specifically, 6 underwent magnetic resonance imaging (MRI) of the brain, and 1 underwent computed tomography of the brain. Three patients had follow-up neuroimaging between 14 and 216 days after their initial studies. All studies were reviewed by an independent neuroradiologist, who had not made the previous radiologic diagnoses of PRES. The patterns of changes as well as evidence of permanent neurologic abnormalities were noted.

To identify the demographic and clinical characteristics that may have led to the decision to order neuroimaging studies, the subgroup of eclamptic patients who underwent imaging (n=7) was compared with the subset of patients who also developed eclampsia but did not undergo brain imaging (n=6). Statistical procedures included the Wilcoxon rank sum test for continuous variables. P <.05 was prespecified as being statistically significant.

Of the 17,317 women who gave birth during the study period, 13 (0.075%) had a diagnosis of eclampsia. Reviews of the medical records confirmed the diagnosis of eclampsia by identifying its characteristic clinical findings: hypertension, proteinuria, and seizure activity. 1 All patients who underwent imaging had neurologic abnormalities and accompanying radiologic findings of PRES ( Table 1 ; Figure, A ). Contrary to the initial report, 7 and consistent with a more recent study, 10 these lesions were not predominantly present in the posterior cerebrum but rather involved other areas of the brain ( Table 1 ). In addition, PRES and eclamptic seizures occurred at an SBP of less than 180 mm Hg in the 5 of 7 patients who underwent imaging ( Table 1 ). Similarly, eclamptic seizures developed at a peak SBP of less than 180 mm Hg in the 4 of 6 patients who did not undergo neuroimaging ( Table 2 ). All patients except one underwent imaging within 48 hours of seizure onset; the remaining patient was evaluated 4 days after the event.

Demographics, Clinical Findings, and Imaging Results of the 7 Patients With Eclampsia Who Underwent Imaging Studies a,b

Magnetic resonance imaging of the head for a 23-year-old woman (gravida 3, para 1) who delivered at 40 weeks gestation after an uneventful pregnancy. Four days after delivery, she developed a dull headache, followed 5 days later by blurred vision and clumsiness. She had a seizure at home, and on admission, was found to be hypertensive, with a blood pressure of 158/86 mm Hg and an estimated urine protein of 349 mg/24 h. Findings on magnetic resonance imaging of the head (A) were consistent with posterior reversible encephalopathy syndrome (PRES). Blood pressure was controlled, and the patient was discharged. Two weeks after initial imaging, follow-up magnetic resonance imaging (B) revealed near-complete resolution of the changes of PRES, with a residual punctate abnormality in the right superior frontal lobe. She continued to have a dull headache. Her systolic blood pressure returned to the low 100s, and her headache subsequently resolved.

Demographics and Clinical Findings of the 6 Patients With Eclampsia Who Did Not Undergo Imaging a,b

We did not observe statistically significant differences in maternal demographics or diagnostic laboratory findings between patients who underwent imaging and those who did not ( Table 3 ). However, 5 of 7 patients who underwent imaging had the onset of seizures between 1 and 9 days after delivery (median, 5 days). Conversely, only 1 of the patients who did not undergo imaging experienced the onset of seizure activity after delivery.

Comparison of Eclamptic Patients With and Without Imaging a,b

Before the onset of seizures, only 2 women were receiving antihypertensive medication (1 in each group). On the day of the seizure, 4 of 7 women who had undergone imaging, and 3 of 6 who had not, received antihypertensive medication. All women received antihypertensive medication by 1 day after the seizure.

Of the patients, 3 underwent follow-up imaging between 2 and 30 weeks postpartum; 2 had resolution of T 2 white matter alterations, whereas 1 patient had a residual punctate abnormality in the right superior frontal region ( Table 1 ).

Our results suggest a strong association between eclampsia and characteristic neuroradiologic PRES findings in a small series of patients who were treated at Mayo Clinic in Rochester, MN. Radiologic evidence of PRES was present in all 7 patients who developed eclamptic seizures and underwent neuroimaging studies. Because symptoms of PRES in nonpregnant patients are similar to the prodromal symptoms of eclampsia, we postulate that cerebral edema and the neuroimaging abnormalities characteristic of PRES may precede the onset of eclamptic seizures. Patients in our study appeared to develop PRES at a lower mean peak SBP (173 mm Hg) than 113 previously reported patients who were treated for PRES at our institution between 1999 and 2009: acute hypertension was present in 86% of these patients, with a mean peak SBP of 191 mm Hg. 11 Of note, 3 patients who are reported in this study were included in that comprehensive series report, but clinical and radiologic findings in pregnant patients were neither separately analyzed nor contrasted to nonpregnant patients. Peak DBP was not significantly different between these groups. In the series by Hinchey et al, 7 for nonpregnant patients who developed hypertensive encephalopathy and PRES (n=4), the highest SBP was documented between 180 and 200 mm Hg. For patients with eclampsia (n=3), the highest SBP ranged between 150 and 170 mm Hg, and for those treated with immunosuppressive therapy (n=7), the peak SBP varied widely and was recorded at less than 180 mm Hg in 5 of 7 patients. Posterior reversible encephalopathy syndrome in these 2 groups, compared with patients with hypertensive encephalopathy from the same report, occurred at lower blood pressure levels, conceivably due to the confounding effects of endothelial dysfunction in patients with eclampsia, and to the direct toxic effects and vasoconstriction in patients treated with calcineurin inhibitors (cyclosporine and tacrolimus).

We did not observe statistically significant differences in maternal demographics or diagnostic laboratory findings between patients who underwent brain imaging and those who did not. However, given the small patient number in each group, our study may have been underpowered to effectively assess these differences. A comparative study of PRES in pregnant vs nonpregnant patients with various PRES etiologies (hypertensive crisis, chemotherapy, vasculitis) demonstrated differences with respect to age, medical history, and occurrence of headaches (87.5% vs 30.8%, respectively); no differences in symptoms, imaging, and outcomes were noted. 12 The study concluded that, despite different triggering events, PRES in pregnant and nonpregnant patients is the same disease entity.

Several clinical studies have indicated that eclamptic seizure activity may occur in patients with minimal elevations in blood pressure. This has fueled the ongoing debate as to the role of hypertension, if any, in the pathogenesis of eclamptic seizures. It is possible that blood pressure alone is not the exclusive cause, and that endothelial dysfunction, which is a hallmark of preeclampsia, is also a contributing factor. Alternatively, pregnancy itself may decrease the threshold at which an elevation in blood pressure may lead to cerebral hyperperfusion and brain edema. 13 Taken together, these data raise an important question, which relates to the current treatment guidelines from the 2000 National High Blood Pressure Education Program Working Group Report on High Blood Pressure in Pregnancy. 1 These guidelines advise the institution of antihypertensive therapy for a DBP of 105 to 110 mm Hg or higher for patients with sudden escalating hypertension or imminent or frank eclampsia. For adolescent patients with a recent DBP of less than 75 mm Hg, these guidelines suggest treatment of persistent DBP of 100 mm Hg or greater. The elevation in SBP at which treatment is indicated, however, has not been defined. A retrospective study of 28 patients who had a stroke in association with severe preeclampsia and eclampsia called for a paradigm shift and recommended treatment with antihypertensive therapy for these patients when the SBP reaches or exceeds 155 to 160 mm Hg. 14 Of note, blood pressure measurements before the stroke were available in 24 patients from this group, and the SBP was 160 mm Hg or greater in 23 (95.5%) of these patients, and 155 mm Hg or greater in all 28 patients. In contrast, the DBP was 105 mm Hg or greater in only 5 (20.8%) of the 24 patients with blood pressure measurements before the stroke. On the basis of our findings of PRES and eclamptic seizures at a peak SBP of less than 180 mm Hg in 5 of 7 patients, we support these recommendations. Appropriate reduction in blood pressure may prevent progression from vasogenic to cytotoxic edema and cerebral infarction and the resultant permanent neurologic deficits. Because abrupt decreases in blood pressure may adversely affect uteroplacental perfusion and fetal status, treatment of hypertension should mandate close maternal blood pressure and fetal monitoring.

On the basis of the results of neuroimaging studies in eclampsia, 2 potential pathophysiologic mechanisms underlying the development of cerebral lesions and seizures have been proposed: vasogenic and cytotoxic edema. 15 - 17 Vasogenic edema occurs as a consequence of an abrupt elevation in blood pressure to greater than 150 mm Hg, which overcomes intrinsic myogenic vasoconstriction, leading to hyperperfusion and subsequent edema. Zeeman et al 18 have shown that patients with preeclampsia or eclampsia develop significantly increased cerebral blood flow, which causes hyperperfusion with resultant vasogenic edema. In contrast, cytotoxic edema may be caused by cerebrovascular “overregulation,” which causes extreme vasospasm and infarction. Vasogenic vs cytotoxic edema can be differentiated using MRI diffusion-weighted imaging (DWI), which detects changes in water distribution in cerebral tissue. The DWI is decreased in vasogenic edema because of increased extracellular fluid but is hyperintense or “bright” in cytotoxic edema due to restricted diffusion. However, in some cases of vasogenic edema, a hyperintense signal may be present due to a “T 2 shine-through” phenomenon. Further discrimination is possible by estimation of the apparent diffusion coefficient (ADC) of the involved tissue. An elevated ADC represents water molecules with increased diffusional motion (ie, vasogenic edema), whereas a decreased ADC represents restricted diffusion, which is consistent with cytotoxic edema. Published data suggest that cerebrovascular events in preeclampsia/eclampsia encompass a spectrum of severity, with reversible vasogenic edema at one extreme and irreversible cytotoxic edema and cerebral ischemia at the other. A prospective study of 27 patients with eclampsia 10 reported that 25 had radiologic evidence of cerebral edema on T 2 -weighted imaging. Hyperintense areas were identified by DWI in 15 of these 25 patients; 12 of these 15 patients had vasogenic edema, as characterized by an increased ADC, and 6 patients had concurrent evidence of cerebral infarction. Five patients demonstrated abnormal neuroradiologic findings 6 to 8 weeks postpartum, presumably caused by gliosis in response to infarction. Similarly, in our study, 1 patient demonstrated residual neuroimaging abnormalities.

Our study raises another important question: should patients with a classical clinical presentation of eclampsia routinely undergo imaging studies, given that the results may or may not affect their treatment? Of note, current management consists of proceeding with expeditious delivery, with administration of magnesium prophylaxis for premonitory signs of eclampsia. The efficacy of magnesium sulfate in preventing eclamptic seizures may be in part related to its ability to reduce cerebral perfusion pressure in preeclamptic patients with high cerebral perfusion pressures at baseline. 19 Our case series clearly demonstrates the current practice of confirming the diagnosis of eclampsia on the basis of the clinical presentation and reserving imaging for patients with atypical presentations, such as those who develop seizures after delivery. In addition, the reversibility of clinical signs and radiologic abnormalities may argue against neuroimaging of patients at risk of PRES. However, several conditions that can present during pregnancy and postpartum, including acute stroke and systemic diseases that are associated with central nervous system vasculitis (such as systemic lupus erythematosus), may mimic eclampsia. Differentiating among these conditions, which may be difficult on clinical grounds alone, may affect treatment and long-term neurologic outcomes. For example, aggressive blood pressure control is desirable in PRES, in contrast to the management recommendations for acute stroke, which permit mild to moderate hypertension. In conclusion, for patients with an uncertain diagnosis, timely imaging and a diagnosis of PRES may lead to more appropriate decisions regarding treatment of hypertension, thus preventing the possible development of permanent neurologic deficits.

Limitations of our study include its retrospective design and the fact that it represents a limited experience from a single tertiary center. In addition, 5 of 7 patients who underwent imaging experienced the onset of seizures after delivery , whereas all except 1 of the patients who did not undergo imaging experienced the onset of seizure activity before delivery . This clearly represents a selection bias, likely introduced by the fact that the differential diagnosis in patients presenting with seizures after delivery is somewhat more complex. Another selection bias stems from the fact that imaging was performed for patients with clinical signs of PRES only in the presence of seizures (ie, patients with eclampsia) and not for those without seizures (ie, patients with preeclampsia), again reflecting common clinical practice. Despite these limitations, our study suggests that the clinical syndrome of eclampsia is associated with anatomical findings recognizable by neuroimaging as PRES, which occurs at lower levels of blood pressure elevation than in the nonpregnant state. In addition, our study clearly identifies the need and sets the stage for a prospective study of clinical and neuroradiologic correlates in pregnant women with clinical signs of PRES at the time of presentation and their long-term neurologic outcomes.

We propose that the therapeutic targets for SBP be included in the guidelines regarding antihypertensive therapy in pregnancy, particularly when associated with the premonitory signs of eclampsia. 1 Further research is needed to determine both the clinical utility of MRI for patients with preeclampsia and the benefit of more aggressive blood pressure control, with the intent of predicting eclampsia and optimizing neurologic outcomes, respectively. As recent epidemiologic data have indicated that preeclampsia is an independent risk factor for stroke later in life 20 and that women who have had eclampsia may experience impaired cognitive functioning later in life, 21 optimization of blood pressure management at the time of delivery may not only improve immediate pregnancy outcomes but may lower the future cerebrovascular impact of these disorders in affected patients.

In our retrospective study in patients with eclampsia, all those who underwent imaging displayed clinical and radiologic findings of PRES. We could find no clinical differences between patients who underwent imaging and those who did not. Several patients developed seizures without a severe elevation of blood pressure. We propose that PRES and the seizures of eclampsia are pathophysiologically related and that eclamptic patients may have seizure onset at lower blood pressures than patients with hypertensive encephalopathy and PRES. On the basis of our results and in the context of previously published work by others, we support the addition of the therapeutic targets for SBP to the guidelines for antihypertensive management of hypertension in pregnancy.