[A case of facial nerve schwannoma extending into the middle cranial fossa with characteristic CT findings].

Facial nerve schwannoma is rare. Since the first description by Schmid, about 150 cases have been reported mainly in the otological field. The authors recently had a case of facial nerve schwannoma with a marked capsular calcification, extending into the middle cranial fossa. A 63-year-old man was admitted to our hospital on June 20, 1986. About 44 years prior to the admission, he noted facial weakness of the right side which gradually progressed. Neurological examination on admission revealed complete right facial paralysis of the peripheral type with loss of taste, right hearing loss, diminution of lacrimal secretion and no reaction to caloric stimulation. Stenvers' view and tomogram of the right temporal bone showed destruction of petrous ridge. CT scan demonstrated bony destruction of the right petrous pyramid and high dense mass lesion, extending into the middle cranial fossa. Peritumoral and intratumoral calcifications, characteristics of facial nerve schwannoma were also noted. Right external carotid angiography demonstrated the tumor was fed by petrous branch of the right middle meningeal artery. On July 11, 1986 right temporal craniotomy and extradural approach to the floor of the petrous portion of the middle cranial fossa were performed. There was an extradural mass which extended to the middle cranial fossa through the destroyed pyramis. The tumor appeared to originate from the geniculate ganglion of the facial nerve and invaded the inner and middle ear which were almost completely removed. Operative specimen demonstrated that the tumor was a schwannoma. Postoperative hearing test and facial nerve function showed no changes as compared with preoperative findings. Similar case reports with CT findings were reviewed.