Perceptual Consequences of Cochlear Deafferentation in Humans.
Naomi F Bramhall, Garnett P McMillan
PMID 38738337WHAT IT FOUND
When standard hearing tests are normal, weaker measures of cochlear nerve input were sometimes linked to tinnitus and speech-in-noise difficulty, especially in older adults or people with noise exposure.
This does not prove cause or a tested treatment.
Key findings
01In young Veterans with tinnitus, EFR magnitude was 2.4 dB lower than in controls after adjustment, and the authors estimated this reduction was similar to more than 20 years of aging.
02Speech-in-noise findings were inconsistent across human studies, but high-risk populations, EFR with a RAM stimulus, or wideband MEMR more often showed weaker measures linked to poorer performance.
03A study found elevated loudness perception in the ear with greater estimated cochlear deafferentation, but clinically significant sound intolerance was unclear.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Cochlear synaptopathy cannot be confirmed in living humans, so the physiological measures are indirect and may reflect other sources of reduced cochlear nerve input. The physiological measures are not specific to synaptopathy and can be affected by inner hair cell loss, spiral ganglion cell loss, or outer hair cell dysfunction. Human studies used different physiological measures, stimuli, populations, and hearing thresholds, making results hard to compare. Several studies had small samples, and findings were mixed or sometimes opposite. Hyperacusis evidence is limited because there is no standard definition or screening tool and few human studies exist. Animal models may not translate to human perception, and no animal study directly compared all of the physiological measures in the same animals.
Declared interests
The authors declared no potential conflicts of interest. The article lists NIH extramural and non-U.S. government research support.
The easy way to misread this
Do not conclude that cochlear synaptopathy has been proven to cause tinnitus, hyperacusis, or speech-in-noise difficulty in humans. The review says synaptopathy cannot be confirmed in living humans, the physiological measures are not specific, and the human speech results were mixed.