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Cochlear synaptopathy is a condition in which noise interrupts the synaptic communication between sensory inner hair cells and low spontaneous rate cochlear nerve fibres. Since these nerve fibres are associated with signal coding in noisy backgrounds, their disruption leads to difficulties in temporal processing and hearing in noise. As hearing thresholds remain within normal limits, cochlear synaptopathy is also termed as ‘noise-induced hidden hearing loss’. Patients with cochlear synaptopathy complain of hearing difficulties in noise. In this study, the authors evaluated the association of listening to music through personal listening devices with cochlear synaptopathy in young adults. They included 50 participants divided equally into a high-risk (HR) and a low-risk (LR) group, based on their estimated total daily noise levels (ETDNL) calculated from their personal listening device level. There was no statistical difference in the pure tone audiometry thresholds between the two groups. Interestingly, none of the participants complained of hearing problems in noise but tinnitus was more common in the HR group. The acoustic reflex thresholds at 2kHz were significantly higher in the HR group than the LR group. In the assessment of speech intelligibility in noise, the signal to noise (SNR) level at which 50% understanding was achieved with headphones was significantly poorer in the HR group. ETDNL negatively correlated with the amplitudes of action potential (AP) on electrocochleography and wave V on auditory brainstem response (ABR) tests, TurMatrix speech intelligibility in noise test, and 50% comprehension level. A positive correlation was found between ETDNL, ABR waves latencies, and contralateral acoustic reflex at 2kHz. This study’s findings of poorer performance in TurMatrix and electrophysiological tests suggests the negative effect of personal listening devices on the auditory system. It would be interesting to further evaluate these with more robust studies.

The possibility of cochlear synaptopathy in young people using a personal listening device.
Bal N, Derinsu U.
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Praneta Kulloo

Lewisham and Greenwich NHS Trust, UK.

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