PRES has a large spectrum of radiological manifestations,
depending on:
- the evolving phase
- the celerity of onset of the clinical picture
- the quickness in initiating the treatment.
It might present with very atypical findings that can be easily confused with other entities.
We present some examples of cases emphasizing on atypical findings:
TYPICAL PRESENTATIONS
Case 1. Hypertensive crisis in a 23-year-old woman,
in the immediate puerperal period.
Blood pressure 230/135 mmHg.
CT and MRI performed the same day,
depicted subcortical areas of vasogenic edema in the classical location (Fig. 1).
Fig. 1: Slight hypodensity of the subcortical white matter of the right parietal lobe on axial NECT (nonenhanced CT) corresponding to an area of hypointensity on T1WI and hyperintensity on FLAIR. No diffusion restriction was present
Case 2. A 15-year-old boy,
6 days after heart transplantation and intensive treatment with immunosuppressive drugs,
with normal blood pressure.
Imaging studies revealed the typical lesions of PRES in the posterior cerebral structures (Fig. 2).
Fig. 2: Contrast-enhanced CT, axial slices: bilateral parietal and right frontal nonenhancing hypodensities, with predominantly subcortical distribution.
MRI: bilateral parietal hyperintensity on FLAIR with small areas of diffusion restriction (DWI/ADC)
ATYPICAL PRESENTATIONS
Case 3. 24-year-old woman with HELLP syndrome and high blood pressure (180/110 mmHg).
She presented with drowsiness,
weariness in upper and lower limbs and gait difficulties.
The patient had an extremely atypical presentation of PRES,
with vasogenic edema of the basal ganglia,
without any other areas involved (Fig. 3).
Fig. 3: Bilateral symmetric hypodensity of the basal ganglia on contrast-enhanced CT. It corresponds to the hypointense areas on T1WI and high intensity on T2WI and FLAIR (vasogenic edema) with small areas of diffusion restriction (DWI/ADC)
She experienced a complete resolution of the clinical manifestations and of the imaging findings within 2 weeks of intensive treatment (Fig. 4).
Fig. 4: Axial T1WI, T2WI and FLAIR (left-right) demonstrating complete resolution of the initial imaging signs after 2 weeks of treatment
The edema of the basal nuclei in PRES was classically described in uremic encephalopathies (uremic syndromes,
glomerulonephritis,
hemolytic-uremic syndrome,
thrombotic thrombocytopenic purpura) [4].
Teaching file. In a case of HELLP syndrome with acute neurological manifestations and basal nuclei imaging findings (alone or in association with other areas),
the diagnostic of PRES should be considered.
Case 4. 54-year-old man,
with long term hypertension,
resistant to treatment,
with acute onset of increased blood pressure (260/150 mmHg).
Extensive bilateral and symmetric vasogenic edema involving all the lobes,
midbrain,
pons,
and cerebellum (Fig. 5,
Fig. 6).
Acute infarct with diffusion restriction in the right internal capsule (Fig. 5).
Fig. 5: Extensive periventricular and deep white matter NECT-hypodensity corresponding to T1WI-hypointensity and FLAIR-hyperintensity (vasogenic edema). Acute infarct with diffusion restriction in the right internal capsule (DWI/ADC)
Signs of chronic cerebellar hemorrhages on SWI sequence were present (Fig. 6).
Fig. 6: Axial NECT and FLAIR showing hypodensity, respectively hyperintensity, involving the midbrain, pons and cerebellum. Signs of chronic cerebellar hemorrhages on SWI sequence
Decrease of the involved areas after 3 weeks of intensive treatment (Fig. 7).
Fig. 7: FLAIR sequences in axial plane after 3 weeks of intensive treatment showing less extension of the previous hyperintense areas
Despite the radiologic improvement the patient experimented a progressive clinical worsening and decortication signs appeared.
Teaching file. Infarcts and hemorrhages in PRES worsen the outcome [5,
6].
Case 5. This is the case of a 85-year-old female,
brought to emergency room with occipital headache,
marked psychomotor agitation,
impaired consciousness and finally transient tetraparesis and syncope which required tracheal intubation.
The clinical manifestations had a sudden onset and a rapid and severe course.
The blood pressure was 230/120mmHg.
The principal suspicion was an acute stroke of posterior circulation.
Therefore,
the patient underwent the study protocol for the stroke,
including nonenhanced-CT,
perfusion-CT (Fig. 8,
Fig. 9) and CT-angiography (Fig. 10).
The unique highlighted finding was a bilateral and symmetrical time-maps and blood-flow delay (TTP,
MTT,
TTD,
CBF) in the perfusion-CT in parieto-occipital territories,
without areas of abnormal CBV.
Fig. 8: NECT (a), perfusion-CT (b-d) and MRI (e-h) at the level of the caudate head. Bilateral and symmetrical TTP delay (b) and CBF decrease (c) in the parietal territories, without CBV impairment (d). No acute findings were depicted on NECT (a), T2WI (e), FLAIR (f) and DWI/ADC (g, h). Legend: TTP-time to peak; CBF-cerebral blood flow; CBV-cerebral blood volume
Fig. 9: NECT (a), perfusion-CT (b-f) and MRI (g-h) at the level of the midbrain and the occipital lobes. Bilateral delay in time-maps (b-d) with blood-flow decrease (e) in the occipital territories, without areas of abnormal CBV (f). NECT (a), T2WI (g) and FLAIR (h) lacked of any significant features. Legend: TTD-time to drain; MTT-mean transit time
The angio-CT showed neither occlusions nor significant stenosis of the cerebral vessels or of the supra-aortic arterial trunks.
Stenosis of the vertebro-basillary system (which could explain this perfusion pattern) was ruled out (Fig. 10).
Fig. 10: CT-angiography revealing normal origin and initial segment (V1) of left (arrow) and hypoplasic right (arrowhead) vertebral arteries, without stenosis, on coronal MIP reconstruction (a), and its other segments (V3-V4) on 3D-reformatted images (b, c). Also the circle of Willis (b), the basilar and posterior cerebral arteries (c) showed no alterations
Afterwards,
in base of the images,
the suspicion of hypertensive encephalopathy arose.
After antihypertensive treatment the patient experienced a quick improvement,
which confirmed the suspicion.
MRI study carried out the next day,
while the patient being completely asymptomatic,
lacked of pathological acute features (Fig. 8 ,
Fig. 9).
This case,
with only time-maps delay on perfusion studies,
without any other signs on MRI/CT,
illustrates a particularly uncommon imaging presentation of PRES.
In this context,
perfusion-CT opens a new line of diagnosis of the incipient PRES.
Teaching file. The aforementioned findings of cerebral perfusion (bilateral and symmetrical delay of TTP/MTT) are one of the first imaging manifestations of PRES,
until any area of edema on FLAIR/T2WI could be identified.
Teaching file. To recognize the causes and radiological features of stroke mimics and false penumbras can help to establish the correct diagnosis and therapy,
and also can avoid the administration of a thrombolytic treatment with its potentially severe adverse reactions in a patient who doesn’t need this treatment [7].
Case 6. 29-year-old male with an acute cocaine intoxication,
with blood pressure 240/140 mmHg,
gait difficulties and paresthesias in both arms.
NECT showed extensive,
bilateral and symmetrical hypodensities of the medulla,
pons,
midbrain,
cerebellum and periventricular white matter which corresponded to vasogenic edema in the MRI performed the same day (Fig. 11).
Fig. 11: Axial NECT shows bilateral and symmetrical hypodensity of the medulla, pons, midbrain, cerebellum and periventricular white matter which corresponds to hypointensity on T1WI and hyperintensity on T2WI and FLAIR. Brainstem swelling can easily be noticed
Small areas of diffusion restriction indicating acute infarcts in the pons,
the subinsular territory of the left middle cerebral artery and probably in the corpus callosum (Fig. 12).
Fig. 12: DWI sequences and ADC maps depicting small areas of diffusion restriction in the pons, the subinsular territory of the left middle cerebral artery and probably in the corpus callosum
The patient had a very slow improvement,
without complete neurological recovery in our last follow up.
Teaching file.
Multiple foci of diffusion restriction are associated with slow or incomplete recovery.
TAKE HOME POINTS
1.The study usually starts with an unenhanced CT,
frequently followed by a contrast-enhanced CT.
It can be completely normal or show from discrete hypodensities to a very extensive involvement with severe cerebral edema.
The next study which all patients should undergo is the MRI.
Its particular importance consists of evaluating the possible ischemic or hemorrhagic complications (Fig. 13).
2.Besides the typical posterior involvement,
as its name suggests,
PRES can affect every other cerebral region,
including the anterior areas,
the brainstem and the basal nuclei.
Also it can be asymmetrical or rarely unilateral [3].
3.It’s very important the assessment of the extension,
the mass effect,
the ischemic signs (DWI),
the presence of hemorrhage (T2*/SWI) and the contrast-enhancing areas.
All of this information is essential to evaluate patient outcome and prognosis (Fig. 13).
Fig. 13: Management of PRES. NECT-nonenhanced CT; CECT-contrast enhanced CT; MRI-magnetic resonance imaging
4.On the contrary to its name,
sometimes it can be irreversible,
complicated with infarcts and hemorrhages and poor outcome [5,
6].
5.PRES is a cause of stroke-mimic and is one of the five described possible causes of false penumbras in the perfusion maps (TTP/MTT delay simulating ischemic penumbra) [7].
Perfusion-CT could open a new line of diagnosis of incipient PRES that could have important clinical implications.
6.An acute presentation of basal nuclei involvement as the principal imaging appearance in a patient with uremic syndrome is typical of uremic encephalopathy [4].
7.In a case of HELLP syndrome with acute neurological manifestations and basal nuclei imaging findings,
the diagnostic of PRES should be considered.