Electrocochleography (ECochG) is another test that measures electrical activity that occurs in response to sound. During ECochG testing, electrical activity that is generated in the hearing portion of the inner ear called the cochlea is measured. Electrical activity from the hearing nerve is also recorded. Preparations for ECochG testing are identical to those described for ABR testing. However, in addition to the four electrodes taped to the head, an electrode, like the one seen at right, is also placed in each ear canal. The ear canal electrode is spongy and soft and is not uncomfortable. Prior to placing the electrode in the ear canal, the ear canal is gently prepped using rubbing alcohol and a mild abrasive agent.
During the testing the patient is reclined in a comfortable chair and encouraged to relax. As is the case during ABR testing, excessive muscle tension may interfere with accurate electrical recordings. Clicking sounds similar, although slightly louder, than those presented during ABR testing are introduced into the ear canals.
As with ABR testing, it is preferable to avoid caffeine the day of the test and arrive for testing somewhat tired if possible. No response is required from the patient. In fact, the patient can sleep during the test session. Changes in the electrical activity recorded from the cochlea may aid in the diagnosis of inner ear disorders, such as Meniere’s disease, perilymphatic fistula, and semicircular canal dehiscence.