Raised intracranial pressure and hydrocephalus following hindbrain decompression for Chiari I malformation: a case series and review of the literature

Object. Chiari-syringomyelia is a heterogeneous condition that may be treated by decompression of the foramen magnum. Raised intracranial pressure (ICP) and/or hydrocephalus is a rare complication of this treatment. We aim to describe the incidence, clinical presentation, radiographic findings, management and outcome of patients developing raised ICP and/or hydrocephalus after hindbrain decompression for Chiari I malformation. Methods. Retrospective analysis of 138 consecutive adult and paediatric patients with Chiari I malformation who underwent foramen magnum decompression. Results. The incidence of post-operative symptomatic raised ICP and/or hydrocephalus in this series was 8.7%. Overall, 9 of 12 patients developing raised ICP or hydrocephalus required a VP shunt, an overall incidence of 6.5%. However, 3 of 12 patients were successfully managed with external ventricular drainage or conservatively. Presentation was with headache or CSF wound leak at a median of 13 days post-operatively. Subdural hygromata were observed in five cases in association with hydrocephalus and urgent drainage to relieve mass effect was required in two cases. At a mean follow up of 36 months, 9 of 12 patients were asymptomatic. Conclusions. There is a risk of requiring a permanent VP shunt associated with decompression for Chiari I even in the absence of ventriculomegaly or signs of raised ICP pre-operatively. Patients presenting with new symptoms or CSF wound leak following FMD mandate investigation to exclude hydrocephalus, raised ICP or subdural hygroma.