Facial nerve schwannoma presenting as a tympanic mass.

A 77-year-old woman presented with a history of a slowly progressive hearing loss. She had no recent history of upper respiratory infection, pulsatile tinnitus, vertigo, disequilibrium, otalgia, hemifacial weakness, paresthesia, or facial spasms.

Otoscopic examination detected evidence of a soft-tissue mass in the middle ear cleft on the right side. The tympanic membranes were clear and mobile bilaterally. A tuning fork test showed that Weber's test lateralized to the right. Rinne's test was negative on the right and positive on the left. Audiometry revealed a high-frequency sensorineural hearing loss with a significant conductive component in the right ear. Facial nerve function was normal bilaterally (House-Brackmann grade I). Contrast-enhanced computed tomography (CT) of the fight temporal bone revealed the presence of a mass that involved the tympanic and mastoid section of the facial nerve (figure 1). The part of the tumor that involved the tympanic section was large enough to disrupt the normal vibratory function of the stapes. This explained the conductive component of the hearing loss.

[FIGURE 1 OMITTED]

The patient declined surgery. She was fitted with a hearing aid, and the status of the tumor was monitored with yearly magnetic resonance imaging (MRI) scans (figure 2). The tumor remained stable during follow-up.

[FIGURE 2 OMITTED]

Gadolinium-enhanced MRI of the temporal bone is the most accurate tool for diagnosing facial nerve tumors. MRI can detect inflammatory changes (such as those caused by herpes zoster infection and otitis media) and Bell's palsy (which can involve the facial nerve); therefore, it can help distinguish inflammation from tumor. (1,2) On MRI, intratemporal schwannomas are hypo- or isointense on T1-weighted images, hyperintense on T2-weighted images, and well enhanced on postcontrast T1-weighted images. (3) High-resolution CT of the temporal bone is complementary in the case of intratemporal lesions; MRI is superior in demonstrating tumor extension, whereas CT provides detailed information about the relationship of the tumor to surrounding bony structures. (4)

References

(1.) Kim CS, Chang SO, Oh SH, et al. Management of intratemporal facial nerve schwannoma. Otol Neurotol 2003;24:312-16.

(2.) Lakhkar BN, Banavali S, Shetty C. Radiological quiz--Head and neck. Ind J Radiol Imag 2000; 10:107-8.

(3.) Chung SY, Kim DI, Lee BH, et al. Facial nerve schwannomas: CT and MR findings. Yonsei Med J 1998;39:148-53.

(4.) Falcioni M, Russo A, Taibah A, Sanna M. Facial nerve tumors. Otol Neurotol 2003;24:942-7.

Sejal P. Sarolia, BS; Christopher J. Danner, MD; Eren Erdem, MD

From the Department of Otolaryngology-Head and Neck Surgery, University of Arkansas for Medical Sciences, Little Rock.