Teaching Case

A 13 year-old boy presented with a single GTC seizure, visual disturbance, headache, altered sensorium and swelling over his whole body. On examination, the patient was drowsy, hypertensive at 170/100 mmHg, and there was oedema over the whole body. Biochemical tests revealed Serum Creatinine of 5.2mg% and BUN of 131mg%

Ultrasound of the kidneys revealed increased renal cortical echogenicity with reduced cortico-medullary differentiation consistent with medical renal parenchymal disease.
MRI demonstrated multiple ill-defined TI hypointense, T2/FLAIR hyperintense patchy areas in the right frontal and bilateral parieto-occipital regions of the cerebral hemispheres, involving both grey and white matter, and showing restricted diffusion on DWI, with no blooming on GRE and no enhancement of the affected areas.

Background:- Posterior Reversible Encephalopathy Syndrome (PRES), also known as Reversible Posterior Leukoencephalopathy syndrome, is a clinical condition characterized by rapid onset of neurological symptoms which are often but not always associated with acute hypertension.[1] It was first described by Hinchey et al in 1996 [2]. The pathophysiology can be explained as when there are acute changes in blood pressure, there are auto-regualtory mechanisms to cope, however, an inability to do so by the posterior circulation leads to PRES. Regardless of the cause, there is disruption of blood brain barrier due to hyperperfusion, thus leading to vasogenic oedema involving the white matter, most commonly the parietal and occipital lobes. The possible explanation behind preferential involvement of the posterior circulation is the paucity of sympathetic innervation in the arterioles supplying the vertebrobasilar system which normally cause the auto-regualtion.[2]
Clinical Perspective:- Clinical presentation includes neurological symptoms like seizures, headache, confusion, visual disturbance etc. The disease is described more commonly in adults like eclampsia patients, however in cases with pre-disposing factors like renal disease or chemotherapy, it can also occur in paediatric population with equal risk. [2] The triggers include acute hypertension, acute kidney injury, sepsis, with immunosuppresive drugs, illicit drugs, organ transplantation, and chronic kidney disease. [1]
Imaging Perspective:- The characteristic imaging appearance is attributed to the vasogenic oedema involving both grey and white matter. Although classically believed to occur in the parieto-occipital lobes, studies have shown it to atypically occur in other areas also such as the posterior frontal and temporal lobes, thalami, and basal ganglia, with varying imaging appearances. [3]
Outcome:- Management is by rapid withdrawal of the trigger factor, which also leads to total reversibility of disease if diagnosed and treated early. The prognosis is good, the clinical syndrome usually resolving within a week, and the MRI changes resolving over days to weeks.[1]
Teaching Point:- Although an entity known to occur commonly in adults, in a child with rapid onset neurological symptoms in the setting of acute hypertension or other associated trigger factors, the possibility of PRES should be kept in mind, as it is a completely reversible disease and any delay in diagnosis and treatment may result in a permanent neurological deficit.

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