Detection of an occult transclival cerebrospinal fluid fistula by CT and MRI

We describe an unusual occult transclival cerebrospinal fluid (CSF) fistula to the sphenoid sinus demonstrated by MRI. CT was performed because of a p osterior cerebral infarct caused by cardiac arrhythmia. Axial sections show ed fluid in the sphenoid sinus. High-resolution scans revealed a bony defec t 3 mm in diameter of the posterior wall of the sphenoid sinus, and MRI sho wed a transclival CSF fistula. This occult lesion was confirmed by surgery and duraplasty was successfully performed via an endonasal approach.