Neurinomas of the facial nerve extending to the middle cranial fossa

Three cases with neurinomas of the facial nerve are reported, especially with regard to the computerized tomographic (CT) findings. All of them had a long history of facial-nerve dysfunction, associated with hearing loss over periods from several to twenty-five years. Intraoperative findings demonstrated that these tumors arose from the intrapetrous portion, the horizontal portion, or the geniculate portion of the facial nerve and that they were located in the middle cranial fossa. The histological diagnoses were neurinomas. CT scans of three cases demonstrated round and low-density masses with marginal high-density areas in the middle cranial fossa, in one associated with diffuse low-density areas in the left temporal and parietal lobes. The low-density areas on CT were thought to be cysts; this was confirmed by surgery. Enhanced CT scans showed irregular enhancement in one case and ring-like enhancement in two cases. High-resolution CT scans of the temporal bone in two cases revealed a soft tissue mass in the middle ear, a well-circumscribed irregular destruction of the anterior aspect of the petrous bone, and calcifications. These findings seemed to be significant features of the neurinomas of the facial nerve extending to the middle cranial fossa. We emphasize that bone-window CT of the temporal bone is most useful in detecting a neurinoma of the facial nerve in its early stage in order to preserve the facial- and acoustic-nerve functions. (author)