Question
I recently diagnosed a 2 year old male with bilateral auditory neuropathy using DPOAEs, TEOAEs and ABR with reversed polarity while under sedation. Due to time constraints in the OR, I was not able to get to ASSR testing, but I would like to know what results have been obtained with ASSR testing in kids with AN by others? Is there any literature or research that correlates ASSR results with cochlear implantation candidacy or outcomes?
Answer
Auditory Steady State Response (ASSR) testing has added greatly to our ability to determine physiologic thresholds in those populations where behavioral testing is not possible or incomplete. ASSR is used primarily in assessing infants and difficult to test populations and in determination of threshold estimations and to increase our ability to detect more accurately physiologic thresholds for hearing aid amplification or cochlear implantation. It should be utilized in conjunction with ABR, especially in ruling out retrocochlear, auditory neuropathy or brainstem dysfunctions. Currently ASSR is not the optimal test for the detecting of Auditory Neuropathy or other retrocochlear lesions. The reason for this is simply that the absence or abnormal ASSR findings could be related to either a sensory loss, conductive loss, mixed loss or neural dysfunction and simply having no ASSR response would not necessarily mean Auditory Neuropathy, etc. Since this test is an objective test (responses determined by statistical algorithms) not by the clinician, and no observable responses are seen, we cannot view any type of waveforms, etc. Furthermore, we have very little research regarding how the ASSR response is affected by neural or retrocochlear abnormalities. Currently there is ongoing research looking at those patients diagnosed with Auditory Neuropathy and the possible effects on the Auditory Steady State Response. From my own clinical perspective we have observed abnormal ASSR findings in those patient populations diagnosed with Auditory Neuropathy, Multiple Sclerosis and Brainstem tumors. It is hoped that as we learn more about the possible affects of neural pathologies on the ASSR and we will be able to utilize this test more for those diagnostic clinical applications, but until then, we should be using ASSR for assessment and determination of physiologic thresholds only. I would highly recommend the use of Otoacoustic Emissions and ABR in the diagnosis of Auditory Neuropathy as you so utilized.
Dr. Steven D. Smith has been an audiologist for 15 years. He is Director of Audiology and Physicians Hearing and Balance Center for ENT Associates of Alabama, P.A. He is also Associated Professor with the Auburn University Au.D. Program and serves as an Adjunct Professor for the Pennsylvania School of Audiology Au.D. and the Arizona School of Health Science Au.D. Programs. Furthermore, he participates in numerous seminars and conferences relating to electrophysiological testing and his research interest are currently ASSR and Stacked ABR.