RADIATION INDUCED HEARING LOSS

Timothy C. Hain, MD. Hearing Page Page last modified: June 14, 2008

Figure 1: The outer ear consists of the auricle (unlabelled), the external auditory canal, and the lateral surface of the tympanic membrane (TM). The middle ear includes the medial surface of the eardrum, the ossicular chain, the eustachian tube, and the tympanic segment of the facial nerve. The inner ear includes the auditory-vestibular nerve, the cochlea and the vestibular system (semicircular canals). The auditory nerve, also called the cochlear nerve, transmits sound to the brain.

Radiation to the area of the ear is often associated with a chronic, progressive hearing deterioration (Wang et al, 2004). Sometimes the radiation has been purposely delivered to treat at tumor of the inner ear area (such as an acoustic neuroma), but more commonly the radiation has been delivered to treat a cancer in the same region. For head and neck cancers, the temporal bone (which contains the inner ear), is often included in the radiation field.

The hearing loss is usually delayed -- with no hearing loss in the first month post surgery but about 50% hearing loss by one year (Yilmaz et al, 2008). OAE testing in the first month can predict which patients are more likely to deteriorate.

Possible adverse effects of radiation to the ear include:

• ear canal necrosis
• temporal bone osteonecrosis otitis media usually with conductive hearing loss
• earache and tinnitus
• stiffness of the ossicular chain and tympanic membrane resembling otosclerosis
• delayed sensorineural hearing loss

Chemotherapy may be combined with radiation, which can also independently cause reduced hearing (generally sensorineural hearing loss) due to ototoxicity.

• Yilmaz YF and others. Sensorineural hearing loss after radiotherapy for head and neck tumors. Otol Neurol 29:461-463, 2008
• Wang LF and others. A long-term study on hearing status in patients with nasopharyngeal carcinoma after radiotherapy. Otol Neurotol 25: 168-173, 2004.