When does low mean high? Isolated cerebral ventricular increased intracranial pressure in a patient with a chiari I malformation

Objective: To present an unusual case of pseudotumor cerebri with increased intracranial pressure isolated to the cerebral ventricles resulting from a Chiari I malformation. Materials and Methods: The patient received a complete ophthalmologic exami nation on initial presentation and subsequent visits. including visual acui ty. pupillary examination, intraocular pressures, dilated fundus examinatio n with assessment of degree of papilledema. and visual field testing. Intra cranial pressure was measured by lumbar puncture and subsequently by intrac ranial pressure bolt monitoring. Magnetic resonance imaging (MRI) was used to diagnose the Chiari I malformation. Results: The patient initially presented with bitemporal headaches. elevate d opening pressure on lumbar puncture, and mild papilledema with a normal M RI. After lumboperitoneal shunt placement and several revisions, the patien t presented with decreased vision OD secondary to Terson syndrome and worse ning papilledema. Subsequent evaluation revealed normal lumbar opening pres sures and a Chiari I malformation. She underwent ventriculoperitoneal shunt placement with resolution of her symptoms. Conclusions: Tonsillar herniation is a well-documented complication of lumb operitoneal shunt revision. Obstruction of cerebrospinal flow through the f oramina of Magendie and Luschka can result in increased intracranial pressu re isolated to the cerebral ventricles. In a patient with signs and symptom s of increased intracranial pressure but normal lumbar opening pressure, a Chiari I malformation should be suspected, particularly with a history of m ultiple lumboperitoneal shunt revisions.