Diffusion-Weighted Magnetic Resonance Imaging: A Diagnostic Tool for Auditory (Axonal) Neuropathy

Area of Science:

• Neuroscience
• Medical Imaging
• Audiology

Background:

• Axonal neuropathies cause sensory deficits, impacting neural transmission.
• Auditory nerve degeneration disrupts sound processing, leading to hearing difficulties.
• Quantifying axonal degeneration is vital for diagnosing and managing auditory disorders.

Purpose of the Study:

• To quantify axonal degeneration in the VIIIth nerve using diffusion MRI.
• To correlate diffusion MRI findings with auditory function in various hearing conditions.

Main Methods:

• Diffusion MRI (dMRI) and hearing tests were performed on 52 participants.
• Participants included those with normal hearing, cochlear hearing loss, and auditory neuropathy (AN).
• Apparent Fibre Density (AFD) was measured in the VIIIth nerve using fixel-based analysis.

Main Results:

• Apparent Fibre Density (AFD) was significantly lower in individuals with auditory neuropathy (AN) compared to controls.
• A strong negative correlation was found between AFD and hearing thresholds in participants without cochlear dysfunction.
• Reduced auditory nerve fiber density, indicated by lower AFD, is associated with impaired sound detection.

Conclusions:

• Diffusion MRI-derived AFD is a sensitive indicator of VIIIth nerve axonal degeneration.
• This study offers in vivo evidence linking auditory nerve microstructure to hearing thresholds.
• dMRI shows potential as a clinical tool for assessing auditory nerve health and guiding AN treatment.