Facial Nerve Neurilemmoma

Abstract

A 53-year-old male died of pulmonary adenocarcinoma, and had no history of facial palsy. At autopsy, the temporal bone revealed a small neurilemmoma in the horizontal portion of the Fallopian canal. The tumor protruded into the tympanic cavity through the eroded bony wall of the Fallopian canal.Intratemporal facial nerve neurilemmomas are relatively uncommon. However, more than 170 cases have been reported in the international literature, including 23 cases from Japan. Most such cases result in progressive or permanent facial palsy. It should be noted that in 19 cases there was no facial palsy and in 15 there was recurrent or fluctuant facial palsy.From the findings of the temporal bone study in our patient, the mechanisms of such interesting clinical behavior of facial nerve neurilemmoma may be explained. The compression effect of such a small tumor which protrudes into the tympanic cavity is not sufficient to produce facial palsy, and the facial palsy produced by the compression effect of the intracanal tumor is improved when the tumor extends through the eroded bony wall and releases the intracanal pressure. Such may be termed “spontaneous decompression”.