Auditory Brainstem Response Norms for Hearing Health

A new study from the VA National Center for Rehabilitative Auditory Research offers clinicians a potential tool to identify hidden hearing damage in patients with normal hearing tests. The research, published in the *American Journal of Audiology*, establishes sex-specific normative ranges for a specific auditory brainstem response (ABR) measurement, which can distinguish individuals with likely cochlear deafferentation—a loss of connections between the inner ear and the brain—even when their standard audiogram is normal.

Measuring the Unseen: The Search for a Diagnostic Tool

Cochlear synaptopathy, often called “hidden hearing loss,” describes damage to the synapses connecting the inner ear’s hair cells to the auditory nerve. This deafferentation can lead to auditory processing problems, such as difficulty understanding speech in noise, tinnitus, or decreased sound tolerance, even when thresholds for pure tones are clinically normal. A significant challenge has been diagnosing this condition in individual patients, rather than just observing trends in group studies.

Lead author Sean D. Kampel and colleagues focused on the amplitude of Wave I in the auditory brainstem response. In animal studies, this ABR component is a well-established indicator of cochlear nerve health. The team’s objectives were to create a reference standard for Wave I amplitude in a low-risk population and then test its diagnostic power in a high-risk group.

How the Study Was Conducted

The researchers assembled two distinct groups. The low-risk, normative sample included 169 young, non-Veteran adults. All had normal audiograms, reported minimal noise exposure history, and confirmed they had no auditory complaints like tinnitus, hyperacusis, or speech-in-noise difficulties.

The high-risk comparison sample consisted of 91 military Veterans. While they also passed standard hearing tests, every Veteran reported at least one persistent auditory complaint. The team measured ABR Wave I amplitudes in response to 2, 4, and 8 kHz tonebursts. They also measured distortion product otoacoustic emissions (DPOAEs), a test of outer hair cell function, to see if adjusting for this variable improved the diagnostic utility of the ABR.

A Clear Signal in the High-Risk Group

The results were telling. The normative ranges, when adjusted for sex, successfully separated the low-risk and high-risk populations. A particularly strong signal emerged at 8 kHz, a frequency important for speech clarity. For a 105 dB stimulus at 8 kHz, 51% of the Veterans in the high-risk sample had Wave I amplitudes that fell below the sex-specific normative range.

An important and somewhat unexpected finding was the role of DPOAE adjustment. The researchers discovered that while DPOAE-adjusted ranges could distinguish the groups, this statistical adjustment might not be necessary for clinical use. The authors suggest that adjusting for outer hair cell function could even be “problematic,” potentially obscuring the clear diagnostic signal provided by the simpler sex-adjusted ABR measure alone.

Why Sex Matters in the Equation

The study confirmed that sex is a significant biological variable in auditory physiology, which is why separate normative ranges for men and women are essential. On average, females tend to have larger Wave I amplitudes than males. Using a single, non-specific normative range would therefore increase the risk of misclassifying individuals, particularly missing deafferentation in women or over-identifying it in men.

Practical Implications for Patients and Clinicians

This research moves the field from theoretical group risk to potential individual diagnosis. For patients who struggle with tinnitus or hyperacusis despite “normal” hearing, an abnormal ABR Wave I amplitude could provide objective validation of their condition. It points to a likely physiological basis in the cochlea or auditory nerve, which can be a crucial step in developing targeted management strategies.

For audiologists and hearing specialists, the study offers a protocol for applying ABR testing in a new way. Using sex-specific normative ranges for Wave I amplitude adds a valuable tool for assessing patients with auditory complaints unexplained by the audiogram. It directly addresses the need for biomarkers of cochlear deafferentation. Clinicians can read more about the fundamentals of this test in our article, “Auditory Brainstem Response: Cochlear Health Indicator”.

Furthermore, this objective measure could help refine our understanding of conditions like misophonia, where emotional reactions to sound may have an underlying auditory processing component. Identifying a subset of patients with co-occurring deafferentation could lead to more personalized treatment approaches.

A Step Toward Personalized Auditory Care

The work by Kampel, McMillan, Heassler, and the rest of the team marks significant progress. By providing a clinically applicable method, they have addressed a major gap in hearing healthcare. The finding that a simple, sex-adjusted ABR Wave I measure is effective simplifies the path to clinical adoption. This tool now allows researchers and clinicians to identify individuals with probable cochlear deafferentation, paving the way for studies on its specific links to perceptual deficits and testing interventions aimed at the neural connection itself.

Source: Kampel SD, McMillan GP, Heassler AE, et al. Normative Ranges for Auditory Brainstem Response Wave I Amplitude: A Potential Diagnostic Indicator of Cochlear Deafferentation. Am J Audiol. 2026; doi: 10.1044/2026_AJA-25-00296. PMID: 42635501.