Facial nerve tumor (mastoid portion). (Imaging Clinic).

Tumors involving the facial nerve are uncommon. These slow-growing masses can arise along any part of the intratemporal course of the facial nerve. The nature of their symptoms and clinical appearance depends on the site of origin. Symptoms include facial nerve paralysis, hearing loss, and vertigo. However, some patients remain asymptomatic for a long period of time.

The most common type of facial nerve tumor is the schwannoma. The first sign of a schwannoma in some patients is facial paralysis. In some cases, the paresis disappears and the patient's condition is misdiagnosed as Bell's palsy. (1) In some patients, the first signs and symptoms of a schwannoma that involves the mastoid portion of the facial nerve are related to tumor protrusion through the posterior wall of the external auditory canal lateral to the tympanic membrane. Other symptoms can include otorrhea, hearing loss, and sudden or gradual facial paralysis. (2,3)

The case presented here is that of a 32-year-old woman whose clinical signs and radiographic findings were consistent with a schwannoma that involved the mastoid portion of the facial nerve on the right. The patient had had a long history of facial paralysis, but her facial dysfunction had been minimal, and for many years she exhibited no significant progressive changes on follow-up imaging examinations; During her most recent evaluation, computed tomography (CT) (figure 1) and magnetic resonance imaging (MMI) (figure 2) detected a tumor that involved the mastoid portion of the facial nerve. Imaging also revealed a fusiform enlargement of the bony canal and the presence of a small mass that protruded into the posterior portion of the external auditory canal.

Reference

(1.) Pulec JL. Facial nerve neuroma, Laryngoscope 1972;82:1160-76.

(2.) Pulec JL. Facial nerve neuroma. Ear Nose Throat J 1994;73:721-2, 725-39, 743-52.

(3.) Pulec JL. Facial nerve tumors: A report of 50 cases. In:L Jahnke K, Fischer M, eds, Proceedings of the 4th European Congress of Oto-Rhino-Laryngology-Head and Neck Surgery, Berlin, May 13-18, 2000. Bologna: Monduzzi Editore, 2000:311-6.

From the Neuroradiology Service, University Hospital Ramon y Cajal, Madrid, Spain (Dr. Peco), and the Department of Radiology, Louisiana State University Health Science Center, New Orleans (Dr. Palacios).