Acute Hydrocephalus Requiring External Ventricular Drainage Following Perimesencephalic Nonaneurysmal Subarachnoid Hemorrhage in a Pediatric Patient: Case Report and Review of the Literature.

Perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSAH) is a well-described subset of subarachnoid hemorrhage with an excellent prognosis in adults. However, its characteristics in the pediatric population have not yet been fully understood. We present a case of acute hydrocephalus requiring external ventricular drainage following pediatric PNSAH. A previously healthy 10-year-old girl was admitted to our neurosurgical department after sudden onset of severe headache with vomiting during exercise. Cerebral non-contrast computed tomography detected subarachnoid hemorrhage filling all perimesencephalic cisterns. However, digital subtraction angiography could not locate the hemorrhage source. Her consciousness deteriorated within 7 hours of onset, and a computed tomography scan revealed acute hydrocephalus. We subjected the patient to external ventricular drainage for 10 days. She was discharged after 38 days of hospitalization, when she was physically and neuropsychologically healthy. Repeated digital subtraction angiography performed at the 6-month follow-up did not show any obvious source of hemorrhage except for a variant drainage pattern of the basal vein of Rosenthal. Based on the observations, we diagnosed the patient with PNSAH of a venous origin. We propose that acute hydrocephalus be suspected in pediatric patients with nonaneurysmal subarachnoid hemorrhage filling all perimesencephalic cisterns, as in adults. We also propose that one of the possible causes of pediatric PNSAH as of venous origin and related to the abnormal drainage pattern of basal vein of Rosenthal and elevation of venous pressure with exercise. Immediate surgical drainage could obtain a good outcome in a symptomatic case. [ABSTRACT FROM AUTHOR]