ELECTRIC RESPONSE AUDIOMETER (ERA)

Although it may be simpler in most cases to test hearing by presenting a sound and asking if it was heard, it is sometimes desirable or necessary to test that the sound has been detected at the cochlea (electrocochleography - ECochG), the brain stem, the cortex (slow vertex response - SVR), or has actuated an auditory reflex (e.g. post auricular muscle response). Apparatus for presenting the stimuli (usually clicks) and detecting the electrical responses are electric response audiometers, and usually contain computer-based signal averagers since the response to a single stimulus might be so small as to be lost in noise.

The need for these tests is where one cannot guarantee that the patient will co-operate fully with conventional audiometry, such as with infants, or with adults who may be exaggerating their symptoms. Also the particular waveforms of the electric responses can assist in diagnosing some of the more obscure conditions.

At present ERA apparatus is only found in special referral centres since there are not large numbers of patients requiring these special tests and there are few staff with the specialized knowledge required for their interpretation. A major expansion in demand may arise in view of the value of the tests in determining hearing loss due to noise exposure at work, and the promise of early diagnosis of deafness in infants.

Content and Design Copyright 2000 Dr. Malcolm C Brown.  See Title Page for more details