Auditory function in hereditary motor and sensory neuropathy (Charcot-Marie-Tooth disease)

Area of Science:

• Neuroscience
• Otolaryngology
• Genetics

Background:

• Hereditary motor and sensory neuropathy (HMSN) is a group of genetic disorders affecting peripheral nerves.
• Auditory dysfunction is not a primary hallmark of HMSN, but its prevalence and characteristics are not fully understood.
• Understanding auditory involvement in HMSN is crucial for comprehensive patient care and management.

Purpose of the Study:

• To investigate the prevalence and nature of auditory dysfunction in patients diagnosed with hereditary motor and sensory neuropathy (HMSN).
• To determine if auditory pathway abnormalities are present even in HMSN patients without subjective hearing complaints.
• To identify the specific components of the auditory system affected in HMSN patients.

Main Methods:

• Pure-tone audiometry was performed on 14 HMSN patients (12 Type I, 2 Type II).
• Further audiological assessments included loudness function, speech audiometry, and brainstem auditory evoked potentials (BAEP).
• Electrocochleography (ECochG) was utilized in one patient for detailed electrophysiological evaluation.

Main Results:

• All 14 HMSN patients exhibited pure-tone audiograms outside the normal range.
• Five patients reported hearing loss; however, one patient without reported hearing impairment also had abnormal audiogram results.
• BAEP and other functional tests indicated that the hearing loss stemmed from dysfunction of the VIII cranial nerve (auditory nerve).

Conclusions:

• Auditory dysfunction, specifically VIII nerve neuropathy, is a common finding in patients with hereditary motor and sensory neuropathy (HMSN).
• Audiological assessment is warranted in HMSN patients, as hearing impairment may be present even without subjective symptoms.
• These findings highlight the systemic nature of HMSN and the importance of evaluating cranial nerve involvement.