Posterior Reversible Posterior Reversible Encephalopathy Syndrome:Encephalopathy Syndrome:

Atypical & Unusual Atypical & Unusual Imaging ManifestationsImaging Manifestations

Petcharunpaisan S.1,2 Ramalho J.1,3 Castillo M.1

1University of North Carolina School of Medicine2 King ChulalongKorn Memorial Hospital, Bangkok, THAILAND

3 Centro Hospitalar de Lisboa Central, EPE, Lisbon, PORTUGAL

eSE number 49

DisclosuresMC: Editor in Chief, AJNRSP: No disclosuresJR: No disclosures

No authors have any activities that could represent a conflict of interest.

Purpose Posterior reversible encephalopathy syndrome

(PRES) is well recognized because of its typical imaging appearance, that is involvement of the parieto-occipital regions

Other brain regions may also be affected and unusual imaging manifestations are observed frequently

Purpose of this presentation is review the less common MR presentations of PRES and their best imaging approach

Typical PRES PRES : a neurotoxic state with unique

imaging appearance Imaging typically shows areas of bilateral

hemispheric edema affecting parietal and occipital lobes, followed by frontal lobes, inferior temporal occipital junctions and cerebellum

Conditions at Risk for PRES

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Typical PRES

A 12 yr-old-girl developed PRES after post streptococcal glomerulonephritis and hypertension.

FLAIR images show high signal symmetrically involving bilateral parieto-occipital, posterior frontal, and temporo-occipital regions.

Unusual Locations► Focal/patchy areas of vasogenic edema

may be seen in: – Basal ganglia and thalami– Brainstem– Deep white matter:

external & internal capsule, corona radiata, splenium of corpus callosum

– Medulla oblongata and spinal cord at least 4 cases described, all are associated with hypertension

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Regional involvement by PRES in a series of 136 patients

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Regional involvement by PRES in a series of 76 patients

Unusual Locations Involvement of basal ganglia, brainstem,

and deep white matter are a less common but recognized part of PRES particularly when associated with abnormalities in the typical location

Isolated unusual location in PRES, e.g.. central PRES with only basal ganglia and brainstem involvement, is rare but well known to occur

Unusual Locations PRES may occasionally present with mini

mal or no detectable parietooccipital edema

In such cases, it is necessary to exclude other causes, such as myelinolysis or encephalomyelitis using clinical history and follow-up imaging, when necessary

Unusual Location

A 6-year old boy with sickle cell anemia presented with alteration of consciousness, headaches and seizures, and found to have hypertension (200/100).

FLAIR images show high signal symmetrically involving bilateral parieto-occipital lobes, frontal lobes, bilateral cerebellar hemispheres and splenium of corpus

callosum.

Unusual Location

39 year-old-female with severe hypertension, developed severe headache and visual disturbances.

FLAIR images show high signal involving bilateral parieto-occipital lobes, frontal lobes, temporal lobes, bilateral basal ganglia, left thalamus, pons and cerebellum.

Unusual Location

A 10-year old boy with pyoderma gangrenosum, presents with headache and seizures.

FLAIR images show high signal in parasagittal frontal lobes, right temporo-occipital lobe, midbrain, right basal ganglia and thalamus, genu of corpus callosum and cerebellum.

Unusual Location

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23 yr-old-male cocaine-induced malignant hypertension, presenting with headaches,

confusion and spinal cord syndrome. T2W images show high signal in bilateral parietal lobes (a), medulla oblongata and cervical cord (b). Four weeks later follow up shows resolution of cord lesions (c).

a b c

Enhancement (up to 37%) : cortical, leptomeningeal, parenchymal or pachymeningeal

Restricted diffusion (11-26%)

Hemorrhage (10.5-17.1%) : parenchymal or subarachnoid

Altered brain perfusion : regional decreased or increased, depends on disease time course

Unilateral hemispheric involvement (2.6%)

Restricted Diffusion

A 66 yr-old-female developed PRES after severe hypertension.

FLAIR image (a) shows high signal involving bilateral parieto-occipital lobes and splenium of the corpus callosum with restricted diffusion on DWI (b) and ADC map (c).

a b c

Cortical Enhancement

A 66 yr-old-female developed PRES after severe hypertension

FLAIR images (a,b) show high signal in bilateral parieto-occipital lobes, cerebellum and splenium of corpus callosum.

Post gadolinium T1WIs (c,d) show cortical enhancement of lesions seen in FLAIR.

dc

ba

Leptomeningeal Enhancement

9 year-old-boy developed PRES due to severe hypertension.

FLAIR images (upper row) show high signal in bilateral parieto-occipital and frontal lobes. Post gadolinium images (bottom row) show leptomeningeal enhancement.

Subarachnoid Hemorrhage

50 yr-old-female developed PRES after severe hypertension.

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FLAIR image (A, B) show high signal in bilateral occipital lobes, abnormal sulcal signal in left frontal region. There is low signal on GRE T2*W (C), corresponding with sulcal hyper attenuation on CT (D) due to subarachnoid hemorrhage.

Parenchymal Hemorrhage

52 yr-old-female post cardiac transplant developed PRES possibly caused by tacrolimus toxicity.

FLAIR images (a,b) show high signal in bilateral parieto-occipital lobes. CT (c) done next day shows parenchymal hemorrhage in previous affected areas.

a b c

Unilateral Involvement

12 yr-old-male presenting with headache and seizures, found to have severe hypertension.

T2W images show high signal predominantly in the left parieto-occipital and left temporal regions.

Decreased Brain Perfusion

A 10-year old boy with pyoderma gangrenosum, presents with headache and seizures. PRES was diagnosed possibly caused by Tacrolimus toxicity.

FLAIR images (a) show unusual locations of PRES with minimal involvement of fronto parietal lobes. ASL map (b) shows decreased perfusion

(blood flow) in bilateral cerebral hemispheres, more on the left side.

a b

Increased Brain Perfusion

A case of 33 yr-old-female with PRES.

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DWI (a) and ADC (b) map show restricted fluid diffusion in bilateral occipital lobes. ASL map (c) shows increased perfusion in affected regions.

a b c

Summary

Neuroradiologists should be aware that atypical imaging manifestations of PRES are more common than commonly perceived

Recognition of atypical variants of PRES can be helpful to manage these patients and avoid complications in a timely manner

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