Cavum veli interpositi: just an anatomical variant or a potentially symptomatic CSF compartmentalization?

Background: The cavum veli interpositi (CVI) usually is a small CSF-containing abnormality of septum pellucidum, asymptomatic and rare after the age of 3 years. When symptomatic, it is large and can be related to psychiatric disorders, syndromic association of mental retardation and seizures or to hydrocephalus. Methods: This is the first reported case of an otherwise healthy pediatric patient with a large CVI experiencing episodes of hypertonic loss of consciousness unrelated to epileptic, cardiologic or psychiatric causes without signs of chronic increase in intracranial pressure (ICP). Results: Supposing a CSF compartmentalization in the CVI as the cause of acute poussés of ICP due to block of CSF pathways and considering the severity of the symptoms, an endoscopic fenestration was performed with a reduction of cyst dimensions. Conclusion: We suggest considering the fenestration of large CVI even in otherwise asymptomatic patients to avoid the risk of CSF compartmentalization with ICP poussés. © 2012 S. Karger AG, Basel.