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Neuroradiology Case of the Week

Case 220

Scott Cassar MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: A 77-year-old male status post right ear cholesteatoma excision with device placement.

Radiological Findings: Stable postoperative changes in the right mastoid. Right sided ossicular chain is not visualized status post surgical excision. There is a wire passing anterior to the round window and the tip is seen within the cochlea.

Diagnosis: Cochlear implant

Discussion: A cochlear implant is an electronic device that provides a sense of sound to someone who is profoundly deaf or severely hard-of-hearing. It does not restore normal hearing, but can provide a person with a representation of sounds that help them to understand speech.
     Cochlear implants bypass damaged portions of the ear and directly stimulate the auditory nerve. This is different than hearing aids which amplify sounds so that they may be detected by damaged ears. In cochlear implants, a microphone, sensing sound from the environment, sends a signal to a speech processor which arranges the sounds into coded electric signals. An external transmitter sends a signal to an internal receiver/stimulator which generates electric impulses. Through a group of electrodes called an electrode array, the signals are sent to different regions of the auditory nerve within the cochlea.
     As of 2005, nearly 22,000 adults and 15,000 children in the United States had received implants. Adults who have lost hearing later in life often are able to associate implant generated sounds with sounds they remember. This enables them to understand speech without visual cues such as lip-reading or sign language. Cochlear implants in children may help them acquire speech and language skills with post implantation speech therapy.

References:

1. http://www.fda.gov/cdrh/cochlear/whatare.html
2. http://www.nidcd.nih.gov/health/hearing/coch.htm