Hydrocephalus in the child with dysraphism.

Hydrocephalus develops in approximately 85% of patients with myelomeningoceles and appears most frequently to result from obstruction to cerebrospinal fluid (CSF) flow within the posterior fossa subarachnoid space and at the tentorial hiatus, due to posterior fossa crowding from the Chiari malformation. The presenting features of hydrocephalus are legion; although signs and symptoms of intracranial hypertension are most common, many patients exhibit more subtle and confusing signs, such as intellectual deterioration or behavioral changes, or those that mimic brainstem compression from the Chiari malformation or spinal cord dysfunction due to tethering or syringomyelia. Prompt recognition of these signs and symptoms will direct appropriate therapy toward shunt revision and will help the clinician avoid potentially unnecessary and more dangerous procedures.