Hidden hearing loss in patients with Charcot-Marie-Tooth disease type 1A

Abstract

The aim of this study was to investigate hidden hearing loss in patients with Charcot-Marie-Tooth disease type 1 A (CMT1A), a common inherited demyelinating neuropathy. By using pure-tone audiometry, 43 patients with CMT1A and 60 healthy controls with normal sound detection abilities were enrolled. Speech perception in quiet and noisy backgrounds, spectral ripple discrimination (SRD), and temporal modulation detection (TMD) were measured. Although CMT1A patients and healthy controls had similar pure-tone thresholds and speech perception scores in a quiet background, CMT1A patients had significantly (p < 0.05) decreased speech perception ability in a noisy background compared to controls. CMT1A patients showed significantly decreased temporal and spectral resolution (both p < 0.05). Also, auditory temporal processing of CMT1A patients was correlated with speech perception in a noisy background (r = 0.447, p < 0.01) and median motor conduction velocity (r = 0.335, p < 0.05). Therefore, we assumed that demyelination of auditory nerve in CMT1A causes defective cochlear neurotransmission, which reduces temporal resolution and speech perception in a noisy background. Because the temporal resolution test was well correlated with the degree of demyelination in auditory and peripheral motor nerves, temporal resolution testing could be performed as an additional marker for CMT1A.

Psychoacoustics and neurophysiological auditory processing in patients with Charcot‐Marie‐Tooth disease types 1A and 2A

“…2a). However, damage to auditory nerve axons and their myelin sheaths would have profound effects on the formation of a detectable averaged compound action potential [4,5,[33][34][35]. Alterations in the synchrony of discharges with the demyelination of the auditory nerve fibers might result in changes in both the amplitude and duration of the averaged nerve responses (Fig.…”

“…Temporal resolution was assessed using a temporal modulation detection test. The temporal modulation detection test was administered using previously described procedures [4,[23][24][25]. Modulated and unmodulated signals were presented monoaurally through an insert earphone (ER-3A, Etymotic Research, Inc., Elk Grove Village, IL, USA) at 65 dBA.…”

“…Spectral resolution was assessed using a spectral-ripple discrimination (SRD) test. The SRD thresholds were determined with stimuli based on a previously established technique [4,27,28]. Three rippled noise tokens, two with a standard ripple phase (reference stimulus) and one with an inverted ripple phase (test stimulus), were presented monoaurally through an insert earphone at 65 dBA.…”

“…Hearing difficulty is also relatively common in CMT disease [4][5][6][7]. Because the cochlear nerve is comprised of peripheral nerve endings, auditory neuropathy due to the demyelinating process and/or axonopathy is known to affect the neural representation of acoustic signals [4,5,8]. Hearing is usually assessed by using pure-tone audiometry, which measures the smallest detectable levels of pure tones.…”

“…To date, auditory-processing deficits have not been widely explored in patients with CMT disease with normal sound-detection ability [4,5,7]. No studies have explored FFRs to speech in CMT disease.…”