Abstract
Background: Diabetes mellitus (DM), a multisystem disorder, is a known etiological entity, leading to several neurological disorders. Among them, nervous system is more commonly affected. In most of the diabetic polyneuropathy cases, sensory symptoms involving both general and special senses predominate. Due to gradual and non-homogenous manifestations, it is not easy to detect its onset. Till now no accepted gold standard has been available for its assessment and diagnosis. In this study, changes in vibration perception threshold (VPT) at different frequencies and auditory perception threshold have been investigated in diabetes patients and healthy controls.

Aims and objectives: Determination of perception threshold of a general sense-vibration sense and a special sense-hearing in normal human subjects and patients of DM and evaluation of perception threshold of the human sensory system by VPT test and pure tone audiometry (PTA) as a diagnostic, prognostic and research tool for diabetic neuropathy.

Materials and Methods: A case–control study, conducted in the department of physiology at medical college, Kolkata, after obtaining approval by the institutional research and ethics committee on 100 cases and 40 control subjects. Testing of vibration sensitivity was performed with the help of tuning forks of frequencies of 128 Hz, 256 Hz, and 512 Hz. Assessment of auditory perception threshold was done by Siemens SD 28 diagnostic audiometer.

Results: All data obtained by the methods described here are tabulated. Graphs and charts are drawn and analyzed by standard statistical methods using Statistical Packages for the Social Sciences (version-16) and MATLAB (version-9). A P < 0.05 was considered as significant. A partial negative correlation was observed between the vibration sensitivity and fasting blood sugar and postprandial blood sugar level of the patient population of DM cases, with a “r” value (Pearson’s correlation coefficient was around −0.5. By PTA, it was found the percentage of rise in auditory threshold is around 92–93% in 8000 Hz frequency, and the results of the t-test yield a very highly significant difference (P < 0.0001) between cases and controls. It was found that 128 Hz and 256 Hz vibration stimuli applied over maxillary prominence are highly sensitive and efficient tools for perception analysis. Pure tone auditory threshold evaluation showed preservation of the right-sided advantage of auditory sensitivity and frequency-dependent loss of hearing in the diabetic study population.

Conclusion: Determination of perception threshold of vibration sense by tuning fork and auditory perception by PTA may be used as an effective, easily performed, and low-cost bedside and also outpatient department-based diagnostic tool in patients with DM.

Key words: Vibration Perception Threshold; Diabetes Mellitus; Diabetic Neuropathy; Sensoryneural Hearing Loss; Pure Tone Audiometry