Normative ranges for auditory brainstem response wave I amplitude: A potential diagnostic indicator of cochlear deafferentation

Purpose While cochlear synaptopathy has limited impact on auditory thresholds, there is increasing evidence that cochlear deafferentation is associated with auditory perceptual deficits. However, there is currently no means for diagnosing synaptopathy or deafferentation in individual patients. The objectives of this study were to establish normative ranges for auditory brainstem response (ABR) wave I amplitude, a measure sensitive to synaptopathy in animals, in a population at low risk for synaptopathy and then compare a population at high-risk for synaptopathy to the normative ranges.

The low-risk sample consisted of 169 non-Veteran young adults with normal audiograms, minimal self-reported noise exposure history, and no auditory complaints (tinnitus, decreased sound tolerance, or speech perception in noise difficulty). ABR wave I amplitude normative ranges were generated for 2, 4, and 8 kHz tonebursts and were statistically adjusted for sex and average distortion product otoacoustic emission (DPOAE) levels. Ninety-one military Veterans with normal audiograms and at least one auditory complaint were included in the high-risk comparison sample.

While the DPOAE-adjusted ABR normative ranges were effective at distinguishing between the low– and high-risk samples, the results also indicated that adjusting the ABR normative ranges for OHC dysfunction may not be necessary and could be problematic. ABR normative ranges that were adjusted only for sex were able to differentiate between the low– and high-risk samples, with 51% of the high-risk sample falling below the normative ranges for a 105 dB peSPL 8 kHz toneburst.

In patients with normal audiograms, sex-specific ABR wave I amplitude normative ranges can be used by clinicians to identify patients with high degrees of cochlear deafferentation. Competing Interest Statement The authors have declared no competing interest. Funding Statement This study was funded by the Department of Veterans Affairs, Veterans Health Administration, Rehabilitation Research and Development Service - Award #C3804-R/I01 RX003804 (to N.F.B) and by resources and facilities at the VA National Center for Rehabilitative Auditory Research (NCRAR) [Center Award #C2361C/I50 RX002361] at the VA Portland Health Care System in Portland, OR. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The VA Portland Health Care System Institutional Review Board gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Footnotes Email addresses: Sean D Kampel: sean.kampel{at}va.gov Garnett P McMillan: garnett.mcmillan{at}va.gov Anne E Heassler: anne.heassler{at}va.gov Nicole K Whittle: nicole.whittle{at}va.gov Haley A Szabo: haley.szabo{at}va.gov Naomi F Bramhall: naomi.bramhall{at}va.gov Conflict of Interest Statement: The authors do not have any conflicts of interests to report.