Facial neuroma of the cerebellopontine angle and the internal auditory canal.

Four cases of facial neuroma confined to the cerebellopontine angle and internal auditory canal are presented. Prior to surgery, three of these were diagnosed as an acoustic tumor. At operation the true diagnosis of facial neuroma was made. The operative procedure was recorded on film and videotape. The magnetic resonance imaging (MRI) and computed tomography (CT) scans were reviewed retrospectively. In the first three cases the tumor was not centered on the axis of the internal auditory canal (IAC), as would be typical of an acoustic neuroma, but instead occupied a position eccentric to this axis. In one case, this eccentricity was marked. A similar appearance in the fourth case enabled the true diagnosis of facial neuroma to be made before surgery. The postoperative behavior of the tumors was unpredictable. The patient with the largest tumor, which was debulked at operation, did not develop a facial palsy. However, a patient with a small tumor which was not biopsied, developed a delayed but complete paralysis from which she subsequently recovered. This small series suggests that it may be possible, by use of the appropriate imaging technique, to diagnose, preoperatively, a cerebellopontine angle facial neuroma which is otherwise indistinguishable from an acoustic neuroma.