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.