Vibrotactile perception in the sole of the foot in people with normal glucose tolerance and type 2 diabetes

Abstract

Aim To evaluate vibrotactile perception thresholds in people with normal glucose tolerance (NGT) and type 2 diabetes (T2DM) in relation to other sensory tests. Methods Nerve function was evaluated in 36 and 42 participants with NGT and T2DM, respectively [mean age 70.0 (1.2) years; males n=40, females n=38]. The mean duration of T2DM was 12.3 (7.3) years. Vibration perception thresholds were measured at four frequencies (8, 16, 32 and 125 Hz) bilaterally on the sole of the foot at first and fifth metatarsal heads using Multifrequency vibrametry and compared to vibration perception thresholds using Biothesiometer (128 Hz) bilaterally (medial malleolus and distal dorsal bony surface of great toes), touch sensation with Semmes-Weinstein monofilament bilaterally (10 g) at three sites on the sole of foot (distal great toe and 1st and 5th metatarsal heads), electrophysiology (amplitude and conduction velocity of sural nerve; right side) and thermal sensory testing (i.e. small diameter nerve fibers; method of limits using Thermotest®). Results Vibration perception and temperature thresholds in the foot and sural nerve function were different between the NGT and T2DM categories. Measuring vibration perception thresholds at lower frequencies with Multifrequency vibrametry, compared to Biothesiometer, both provided similar correlations to the amplitude of the sural nerve. Temperature thresholds did also correlate with vibration perception thresholds and with sural nerve function. Only 4/42 participants with T2DM showed pathology by monofilament test, none with NGT. Conclusions Vibration perception thresholds have a fair correlation to amplitude of the sural nerve, even when measured at a non-tactile surface. Thus in the present study, measuring vibration perception threshold at a tactile surface does not seem to provide any clear advantage over the traditional way of measuring vibration perception on the medial malleolus. In people with T2DM, both large and small diameter nerve fibers seem to be affected.