Hearing loss caused by damage to the auditory nerve

January 23, 2015 by Elise Boucher-Doddridge

Nerf auditif

The auditory nerve is the 8th cranial nerve. Located in the brain, it courses to the inner ear. The auditory nerve is divided into two branches, the cochlear nerve and the vestibular nerve. The cochlear nerve transmits auditory information to the inner ear. The vestibular nerve is responsible for maintaining balance.

The most common symptoms of auditory nerve damage are sensorineural hearing loss and/or dizziness, among others. Furthermore, damage to the cochlear portion of the nerve (called retrocochlear damage) leads to poor results in speech intelligibility (clarity) tests in comparison with someone who has hearing loss in the same degree but of cochlear origin.

Auditory nerve damage can be caused by several factors. First of all, a nerve injury may occur after trauma, an infection (e.g. meningitis) or even the use of ototoxic medications such as certain antibiotics, often given in high doses, or some cancer drugs.

Secondly, an acoustic neurinoma (also known as vestibular schwannoma) can form on the auditory nerve. This is a benign nerve tumour (on the cochlear or vestibular portion) which appears spontaneously, with no associated family history. It affects approximately one or two in 100,000 people. Most common symptoms include unilateral hearing loss on the side the tumour appears, unilateral tinnitus and dizziness.

While rarer, another cause may be auditive neuropathy, which is characterized by damage to the auditory nerve or to the junction between the auditory nerve and internal hair cells, despite healthy external hair cells. This pathology stands out for a number of reasons, including speech-perception difficulties in silent, and even more so in noisy environments, despite sound amplification.

In short, the auditory nerve plays an essential role in transferring auditory information to the brain and in maintaining balance. Any damage can therefore result in significant difficulties in terms of hearing and balance.

If you think you may be experiencing hearing loss or are at risk, do not hesitate to consult an ENT doctor or audiologist.

References:

– BINDER, D.K., D.C. SONNE, and N.J. FISCHBEIN (2010). Cranial Nerves:
Anatomy, Pathology, Imaging
, New York: Thieme, 230 pages.

-GAL, T.J., J. SHINN, and B. HUANG (2010). “Current epidemiology and management trends in acoustic neuroma”, Otolaryngology – Head and Neck Surgery, 142: 677-681.