eSE number 49
Posterior Reversible
Encephalopathy Syndrome:
Atypical & Unusual
Imaging Manifestations
Petcharunpaisan S.1,2 Ramalho J.1,3 Castillo M.1
1University
of North Carolina School of Medicine
2 King ChulalongKorn Memorial Hospital, Bangkok, THAILAND
3 Centro Hospitalar de Lisboa Central, EPE, Lisbon, PORTUGAL
Disclosures
MC: Editor in Chief, AJNR
SP: No disclosures
JR: 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
AJR 2008;29:1036-42
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
Regional involvement by PRES
in a series of 136 patients
AJNR 2007;28:1302-07
Regional involvement by PRES
in a series of 76 patients
AJR 2007;189:904–912
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
minimal 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
a
b
c
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).
RadioGraphics 2007; 27:919–940
 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
b
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).
c
Cortical Enhancement
A 66 yr-old-female developed
PRES after severe hypertension
a
b
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.
c
d
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.
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.
AJNR 2009;30:1371–79
Parenchymal Hemorrhage
a
b
c
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.
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
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.
b
Increased Brain Perfusion
a
b
c
A case of 33 yr-old-female with PRES.
DWI (a) and ADC (b) map show restricted fluid diffusion in bilateral occipital
lobes. ASL map (c) shows increased perfusion in affected regions.
AJNR 2008;29:1428-35
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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