Audiological findings from an adult with thin cochlear nerves

Abstract

Reported here are audiological findings from an adult with thin cochlear nerves. Magnetic resonance imaging (MRI) revealed that he had a thinner cochlear nerve in the left ear than in the right ear. He had a higher degree of hearing loss in the left ear and poor speech recognition scores for both ears. He had normal middle ear and cochlear functioning. The auditory brainstem response and acoustic reflexes were absent, indicating a retrocochlear pathology. Long latency responses (LLR) revealed normal cortical functioning. Hence, implantation of an auditory brainstem implant might be an option, but the patient would need to be aware of its limitations. This case highlights the importance of MRI in evaluating congenital malformations of the cochlear nerve when audiological findings indicate a retrocochlear pathology.

Keywords: Magnetic resonance imaging; auditory brainstem response; cochlear nerve; long latency responses.

Figure 1.

MRI of the left and right cochlea showing abnormal cochlear nerves with respect to the facial canal. MRI, magnetic resonance imaging.

Figure 2.

A pure tone audiogram showing air- and bone-conduction thresholds for the left and right ear. Thresholds for the right ear are plotted in red and those for the left ear are plotted in blue.