Normal pressure hydrocephalus associated with a small vestibular schwannoma without significant cerebrospinal fluid pathway obstruction: a case report

Hydrocephalus associated with vestibular schwannoma (VS) usually results from obstruction by large tumors. Communicating hydrocephalus associated with small VSs is rare and has traditionally been attributed to elevated cerebrospinal fluid (CSF) protein. A 59-year-old woman with right-sided hearing loss had a Koos grade I intracanalicular VS that enlarged to approximately 12 mm during 3.5 years of surveillance. She reported progressive gait disturbance during evaluation for Gamma Knife radiosurgery. Imaging showed features resembling normal pressure hydrocephalus (NPH): ventriculomegaly (Evans’ ratio, 0.34), a narrowed callosal angle (70.7°), and a disproportionately enlarged subarachnoid space hydrocephalus pattern, without fourth ventricular compression or aqueductal stenosis. Lumbar puncture revealed a normal opening pressure of 90 mmH2O and unremarkable CSF without significant protein elevation; removal of 35 mL of CSF temporarily improved her gait. She underwent ventriculoperitoneal shunting with a programmable valve and, separately, radiosurgery. At 3 weeks postoperatively, ventriculomegaly had partially improved, but gait improvement remained limited. This case suggests that VS-associated communicating hydrocephalus can occur without CSF obstruction or hyperproteinorrhachia and is likely multifactorial. Because the condition may be mistaken for idiopathic NPH or aging, a tap test should be considered when patients with VS develop NPH-like symptoms, regardless of tumor size. CSF diversion is warranted in confirmed cases.