Third ventriculostomy for hydrocephalus associated with spinal dysraphism: indications and contraindications.

Twenty-five patients have undergone this procedure at our unit. These constitute 25% of our total experience with endoscopic third ventriculostomy (4). In the patients under 6 months of age, only one out of 11 patients has had a successful long-term result despite initial good fenestration of the floor of the third ventricle. These patients were selected on the basis of their adequate third ventricular size and a relatively slowly progressive hydrocephalus. Fourteen patients had a ventriculostomy performed instead of shunt revision. In 13 patients this has been a success long term. All of these patients had a Heyer-Schulte valve with antisiphon device installed for months, or more often, years, prior to the third ventriculestomy. We believe that the difference in these two groups is due to a very poor cerebrospinal fluid(CSF)-resorptive capability in patients immediately after back closure due to the prior venting of CSF into the amniotic sac. The absorptive capacity seems to improve with the passage of time in our patients who have had a shunt system that maintains a relatively normal intracranial pressure and thus contributes to the development of the patient's CSF-absorptive system.