Slit Ventricle Syndrome Leads to 10-Year History of Repetitive Transient Central Herniation Masquerading as Seizures: Hydrocephalus Case Report.

Slit-ventricle syndrome (SVS) is a recognized complication of ventricular shunt malfunction, resulting in cyclical symptoms without ventricular dilatation. We present a case of SVS with transient, repetitive, and progressive signs of brainstem herniation evidenced by pupillary dilatation, posturing, and unresponsiveness, with diffuse voltage attenuation on electroencephalogram (EEG).A 32-year-old female presented with a history of hydrocephalus and ventriculoperitoneal shunt placement at 9 months of age. She began experiencing significant headaches in college, later accompanied by stereotypical 5- to 25-minute episodes of unresponsiveness, posturing and pupillary dilatation, and failing anticonvulsant therapy. No neurosurgical evaluation was sought because of small ventricles on brain imaging. Episodes became progressively more frequent over a 10-year period, eventually occurring daily. On presentation, 5 clinical events were captured on EEG over 12 hours of monitoring. With each episode, she became unresponsive and hypertensive, with fixed, dilated pupils and flexor posturing. Between events, she was awake and alert, without confusion or postictal state. She had papilledema and limited extraocular movements, with normal pupils and vital signs. Computed tomography scanning showed small ventricles. A shunt tap revealed no flow. With each episode onset, an EEG revealed an abrupt background rhythm slowing to 2-3 Hz delta range without epileptiform discharges. Between events, EEGs displayed normal waveform activity. Emergent ventriculoperitoneal shunt revision resulted in no further episodes in a 4-year follow-up period.SVS can lead to severe intermittent brainstem herniation syndrome in the setting of shunt malfunction. Seizure diagnosis should be reserved for cases with proven functional shunt and EEG confirmation of epileptiform activity.