Individual Differences in Auditory Brainstem Response Wave Characteristics: Relations to Different Aspects of Peripheral Hearing Loss.
Sarah Verhulst, Anoop Jagadeesh, Manfred Mauermann and 1 others
PMID 27837052WHAT IT FOUND
ABR growth ratios may help separate hair-cell loss from auditory nerve loss, but measurements in 30 listeners did not show a clear link to the earliest nerve response.
This metric is not ready for clinical diagnosis.
Key findings
01Simulated ABR wave growth suggested that hair-cell loss steepens both latency and amplitude growth, while nerve-fiber loss mainly reduces amplitude without strongly changing latency growth.
02In listeners with audiogram slopes above 20 dB, Wave-V amplitudes were lower and Wave-V latencies were longer than in listeners with shallower slopes at the tested levels.
03The proposed ABR growth ratio did not show a systematic relationship with Wave-I amplitude in the measured listeners, and there was no direct physiological evidence that abnormal ratios meant nerve-fiber loss.
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What it does not show
Only 30 adults were measured, and some ABR responses were not measurable at the lowest stimulus levels in listeners with hearing loss. There was no direct physiological evidence that listeners with larger absolute ABR growth ratios actually had nerve-fiber loss. The model did not include age-related central gain mechanisms that may affect Wave-V/I ratios. Head size effects were not tested, and Wave-I amplitudes can be influenced by sex and head size. It is unclear whether the proposed growth ratio generalizes beyond high-frequency sloping hearing loss, especially to flat audiometric loss. Wave-I amplitudes showed large standard deviations even with 7,000 averages, and variability can propagate into relative metrics, so clinical sensitivity is uncertain.
The easy way to misread this
Do not use an abnormal ABR growth ratio to diagnose nerve-fiber loss in patients with hearing loss. The study had no direct physiological evidence that such ratios reflected nerve-fiber loss, and in 30 listeners the ratio did not show a systematic relationship with Wave-I amplitude.