Auditory Neuropathy (Dys-Synchrony)

The first time I remember encountering a child with what turned out to be auditory neuropathy (dys-synchrony) (AN) was about 1996. I had followed a pre-school-aged child, first finding an abnormal auditory brainstem response (ABR) and then fitting her with amplification. Her young mother was inconsistent in putting the hearing aids on her daughter, insisting that her daughter ``heard'' and ``danced to music.'' I found out later that her daughter had normal otoacoustic emissions (OAEs) and fairly good behavioral response to auditory stimuli. I have not seen her for several years, but the message stayed with me: the ABR does not tell the whole story.

Auditory neuropathy (dys-synchrony) is a puzzling disorder and one that, as newborn hearing screening becomes more the standard, audiologists will see more frequently. In this issue of Seminars, Yvonne Sininger estimates that as many as 10% of infants and children diagnosed as deaf by ABR have auditory neuropathy (dys-synchrony) rather than sensory hearing impairment. Newborn hearing screening (NBHS) programs that rely solely on otoacoustic emissions will fail to uncover this disorder, yet NBHS programs (or diagnostic audiologists) that rely solely on ABR will fail to appreciate the locus of the auditory impairment.

In at least two children that I am currently following, auditory neuropathy (dys-synchrony) is clear by ABR: the presence of the cochlear microphonic (CM) that inverts with inverting stimulus polarity, with absence of all subsequent waveforms. Yet, in both of these children, the presence of OAE has never been established because of chronic middle ear effusion. Diagnosing AN in infants and toddlers may be impeded by the presence of middle ear effusion, yet, with careful attention to the details of recording the ABR, auditory neuropathy (dys-synchrony) may still be detected.

What to do with these children? This question, with its variety of answers and lack of answers, was what prompted me to say ``yes'' to Catherine Palmer when she was searching for a guest editor for this edition of Seminars. I selfishly wanted to see a reference that would help me counsel patients and help them make informed rehabilitation decisions. My thanks to the authors of this edition for their insightful and informative views on the diagnosis and rehabilitation of auditory neuropathy (dys-synchrony).

Note: Currently there is no consensus on a correct term for this disorder and, perhaps more important, it is not clear that this is truly one disorder. You will see the descriptor auditory neuropathy and/or auditory dys-synchrony used throughout this issue. These terms acknowledge the potential neural involvement as well as the lack of synchrony in the system. Hood and Berlin provide further guidance to correct terminology in their articles in this issue.