Vibrotactile sense in median and ulnar nerve innervated fingers of men with Type 2 diabetes, normal or impaired glucose tolerance

Abstract

To investigate vibrotactile sense (large fibre neuropathy) at different frequencies in index and little fingers (median and ulnar nerves, respectively) of subjects with diabetes, or impaired (IGT) or normal glucose tolerance (NGT). Vibration thresholds (tactilometry at seven frequencies (8, 16, 32, 64, 125, 250 and 500 Hz)) and median nerve function (electrophysiology) were examined in men (age 73.4 +/- 0.12 years; n = 58, mean +/- sd) with persistent NGT (n = 28) or IGT (n = 7) or with Type 2 diabetes mellitus (T2DM) (n = 23) for > 15 years. HbA1c was increased and vibrotactile sense (sensibility index) was impaired in index and little fingers in men with T2DM. Vibration thresholds were particularly increased at 16, 250 and 500 Hz in the little finger (ulnar nerve). T2DM subjects showed electrophysiological (gold standard) signs of neuropathy in the median nerve. Although subjects with persistent IGT had higher HbA1c, vibrotactile sensation and electrophysiology remained normal. HbA1c did not correlate with vibrotactile sense or electrophysiology, but the latter two correlated with respect to Z-score (sign of neuropathy) in forearm (NGT) and at wrist level (NGT and DM). Vibration thresholds are increased in the finger pulps in T2DM subjects, particularly at specific frequencies in ulnar nerve innervated finger pulps. Neuropathy is not present in IGT. Tactilometry, with a multi-frequency approach, is a sensitive technique to screen for large fibre neuropathy in T2DM. Frequency-related changes may mirror dysfunction of various receptors.