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Acute Hypertensive Encephalopathy, Posterior Reversible Encephalopathy Syndrome (PRES)


KEY FACTS

Terminology

  • Cerebrovascular autoregulatory disorder

  • Many etiologies with HTN as common component

    • Preeclampsia, eclampsia

    • Drug toxicity (e.g., chemotherapy)

    • Uremic encephalopathies

Imaging

  • General

    • Patchy parietooccipital cortical/subcortical edema in patient with severe acute/subacute HTN

  • CT

    • Bilateral nonconfluent hypodense foci

    • ± symmetric lesions in basal ganglia

  • MR

    • Parietooccipital T2/FLAIR hyperintensities in 95%

    • ± basal ganglia, pontine, cerebellar involvement

    • 3 patterns of hemorrhage: Focal parenchymal hemorrhage, microhemorrhages, convexity SAH

    • Generally no restriction on DWI

    • Variable patchy enhancement

    • However, atypical imaging patterns common

Top Differential Diagnoses

  • Acute cerebral ischemia-infarction

  • Status epilepticus

  • Hypoglycemia

  • Thrombotic microangiopathies (DIC, TTP, malignant HTN)

Pathology

  • Acute HTN damages vascular endothelium; failed autoregulation causes blood-brain barrier disruption

  • Result = vasogenic (not cytotoxic) edema

Clinical Issues

  • Headache, seizure, ↓ mental status, visual symptoms

  • Caution: Some patients may be normotensive or have only minimally elevated BP

Axial graphic shows the classic posterior circulation cortical/subcortical vasogenic edema
characteristic of posterior reversible encephalopathy syndrome (PRES). Petechial hemorrhage
occurs in some cases.

Gross pathology of a patient with complicated PRES demonstrates diffuse cerebral edema with swollen gyri. Multifocal petechial microhemorrhages are present in the occipital cortex
with several areas of focal encephalomalacia secondary to infarction
.

(Courtesy R. Hewlett, MD.)

Axial NECT in a 54-year-old patient with liver transplant on Tacrolimus FK 506 who presented with seizures demonstrates asymmetric subcortical edema in the occipital lobes bilaterally
. Findings are typical of PRES.

Axial FLAIR MR in a 20-year-old eclamptic woman who presented with severe hypertension, seizures, and altered sensorium shows classic findings of PRES with occipital cortical/subcortical edema
. Her BP at presentation was 210/140.

TERMINOLOGY

Abbreviations

  • Posterior reversible encephalopathy syndrome (PRES)

Synonyms

  • Hypertensive encephalopathy

  • Reversible posterior leukoencephalopathy syndrome (RPLS)

Definitions

  • Variant of hypertensive encephalopathy characterized by headache, visual disturbances, altered mental function

  • Cerebrovascular autoregulatory disorder

    • Multiple etiologies

    • Most caused by acute hypertension (HTN)

IMAGING

General Features

  • Best diagnostic clue

    • Patchy parietooccipital cortical/subcortical edema in patient with severe acute/subacute HTN

  • Location

    • Most common: Cortex, subcortical white matter

      • –

        Parietooccipital lobes (85-95 %)

      • –

        Frontal lobes (75-77%), temporal lobes (65%), cerebellum (50-55%)

      • –

        At junctions of vascular watershed zones

      • –

        Usually bilateral, often somewhat asymmetric

    • Less common: Basal ganglia

    • Rare: Predominant/exclusive brainstem involvement

  • Size

    • Extent of abnormalities highly variable

  • Morphology

    • Patchy > confluent; atypical patterns common

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