Case of the week Details

• Cortical and subcortical FLAIR hyperintensities in the bilateral frontal and parieto-occipital lobes. Subtle FLAIR hyperintensities in the bilateral basal ganglia
• Subtle FLAIR hyperintensities in the dorsal pons.
• Blooming foci within bilateral parieto-occipital lobes and right cerebellar hemisphere – suggestive of hemorrhage
• Areas of gyral diffusion restriction in the bilateral parieto-occipital lobes.

DIAGNOSIS

• Atypical posterior reversible encephalopathy syndrome.

DISCUSSION

• 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.
• Typical MRI appearance of PRES includes T2W and FLAIR hyperintensities in the parieto-occipital lobes.

Atypical presentation of PRES:

1.Involvement of atypical regions:

• Isolated involvement of deep gray nuclei
• Brainstem/cerebellar hemispheres
• Spinal cord without cerebral hemispheric involvement.

2.Hemorrhage in PRES:

• Focal petechial/microhemorrhages (<5 mm), sulcal subarachnoid hemorrhage and focal hematoma formation.
• Hemorrhage was significantly more common in patients following bone marrow transplantation than in solid organ transplantation.

3. Diffusion restriction in PRES:

• Vasogenic edema predominates in PRES, however cases may be complicated by the development of cytotoxic edema as indicated by diffusion restriction.

4. CONTRAST ENHANCEMENT IN PRES:

• Contrast enhancement has been variably reported in the setting of PRES, typically presenting as leptomeningeal or gyral cortical enhancement.
• PRES complicated by hemorrhage had a poor clinical outcome.
• Death was seen in 50% of the patients who exhibited diffusion signal changes.
• Additionally, brainstem involvement by PRES is associated with a poorer outcome.

Differential Diagnosis:

• Inflammatory cerebral amyloid angiopathy
• Severe hypoglycemia
• Posterior circulation infarct
• Hypertensive brainstem encephalopathy
• Sagittal sinus thrombosis
• Hypoxic-ischemic encephalopathy
• SMART syndrome

References

• Saad AF, Chaudhari R, Wintermark M. Imaging of atypical and complicated posterior reversible encephalopathy syndrome. Frontiers in neurology. 2019 Sep 4;10:964.
• Aracki-Trenki? A, Stojanov D, Trenki? M, Radovanovi? Z, Ignjatovi? J, Risti? S, Trenki?-Bozinovi? M. Atypical presentation of posterior reversible encephalopathy syndrome: clinical and radiological characteristics in eclamptic patients. Bosnian journal of basic medical sciences. 2016 Aug;16(3):180.

Dr Harsha Chadaga
Senior Consultant and Head of Radiology
Manipal Hospital, Yeshwanthpur Bengaluru

Dr Rashmi Jayakar Poojary
Radiology Resident
Manipal Hospital, Yeshwanthpur Bengaluru