Authors: Rajesh Raveendran¹, Prawin Kumar¹, Niraj Kumar Singh¹, Kumari Apeksha¹, Vipin Ghosh², M. Bhanukumar³
¹All India Institute of Speech and Hearing
²JSS Institute of Speech and Hearing
³JSS Medical College
Background: Type 2 diabetes mellitus (T2DM) is a systemic disease prevalent in over 90% of the population with DM. T2DM leads to long-term complications, which include macroangiopathy, retinopathy, nephropathy, and neuropathy, affecting nearly every organ system. In addition, inner ear impairment is a commonly observed yet often neglected and less-reported complication of T2DM. Therefore, the present study aimed to investigate the integrity of the neural transmission of the vestibulocochlear nerve in individuals with T2DM.
Methods: Eighty individuals aged 40-70 years (40 with T2DM and 40 age-matched healthy controls) underwent speech-evoked auditory brainstem response (S-ABR) and late latency response (S-LLR), 500-Hz tone burst evoked cervical vestibular evoked myogenic potential (cVEMP), and ocular vestibular evoked myogenic potential (oVEMP) to assess the integrity of vestibulocochlear nerve branches, respectively.
Results: The comparison of response rates between the groups showed a significantly lower response prevalence in T2DM than in the healthy controls for cVEMP and oVEMP only (p<0.05). The latencies and amplitude measures revealed no significant differences between the groups for the auditory evoked potentials (p > 0.05). While there were no significant differences in absolute latency measures between the groups (p>0.05), the rectified and absolute peak-to-peak amplitudes of cVEMP and oVEMP, respectively, were significantly higher in T2DM than in the control group (p<0.05).
Conclusions: Our results show no significant differences between T2DM and controls in any response parameters assessing the neural mechanisms underlying speech processing. However, individuals with T2DM were found to have a lower prevalence of VEMPs and smaller VEMP amplitudes than their healthy counterparts. While T2DM might affect various parts of the vestibulocochlear nerve, the extent of its damage and its mechanisms are not completely deciphered yet. These findings highlight the need for a standardized test battery to diagnose diabetes-related vestibulocochlear nerve impairment and tailor appropriate management options.
