Endoscopic Fenestration of a Symptomatic Porencephalic Cyst in an Adult

A porencephalic cyst is an aberrant accumulation of cerebrospinal fluid within the brain parenchyma. Its occurrence is rare, with an incidence of 3.5 per 100,000 live births. Etiology is considered the result of perinatal cerebral ischemia or hemorrhage, leading to parenchymal loss. Porencephalic cysts are diagnosed radiologically, and management depends on the clinical manifestation. Our case depicts a porencephalic cyst presenting with nondominant parietal lobe symptoms in adulthood. We hypothesize that a membrane between the cyst and ventricle allowed formation of a 1-way valve that led to slowly progressive cyst enlargement, eventually causing mass effect and nondominant parietal lobe symptoms. Endoscopic fenestration of the cyst membrane into the lateral ventricle was successful in reducing cyst volume and improving mass effect.