Cystic cavum veli interpositi associated with normal or low pressure hydrocephalus.

A new clinical syndrome, characterized by progressive increase in head size (without intracranial hypertension), variable delay in milestones, moderate ventricular dilation, and the presence of a cavum veli interpositi is herein described. The arteriographic and venographic signs are suggestive, but not diagnostic, of the presence of a cavum veli interpositi. Pneumoencephalography, with adequate filling of the subarachnoid spaces and ventricles, is essential to confirming the diagnosis. Cerebrospinal fluid shunting appears to result in an improvement, but the results cannot as yet be considered definitive since only 10 of our 29 patients were shunted.