Hidden hearing loss in a Charcot-Marie-Tooth type 1A mouse model

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Otolaryngology

Background:

• Hidden hearing loss (HHL) is characterized by normal hearing thresholds but impaired auditory nerve function.
• While inner hair cell (IHC) synaptopathy is a known cause, auditory nerve (AN) demyelination is an emerging factor.
• Charcot-Marie-Tooth type 1A (CMT1A) is a prevalent hereditary peripheral neuropathy.

Purpose of the Study:

• To investigate the role of peripheral myelinopathy in causing HHL using a CMT1A mouse model.
• To examine the functional and structural changes in the auditory nerve associated with CMT1A.
• To explore the potential for CMT1A patients to serve as a model for studying HHL.

Main Methods:

• Utilized a mouse model of Charcot-Marie-Tooth type 1A (CMT1A).
• Assessed auditory function through electrophysiological recordings, including sound-evoked cochlear compound action potentials.
• Examined the structure of the auditory nerve, focusing on myelination and heminodes near inner hair cells.

Main Results:

• CMT1A mice displayed functional characteristics of HHL, including reduced auditory nerve responses.
• Observed disorganization of auditory nerve heminodes and minor fiber loss near inner hair cells.
• These findings support demyelination as a cause of HHL and link heminodal defects to altered auditory potentials.

Conclusions:

• Mild disruptions in auditory nerve myelination, as seen in CMT1A, can lead to hidden hearing loss.
• Patients with CMT1A and similar peripheral neuropathies are likely to experience HHL.
• Studying hearing in CMT1A patients may aid in developing clinical diagnostic tests for HHL.