Vibratory perception threshold in diabetic neuropathy

A total of 263 diabetic patients and 129 normal controls were enrolled in a study of vibratory perception threshold (VPT) using an electromagnetic vibrometer at two sites, the dorsum of the metacarpal bone of the index finger (IF) and the dorsomedial aspect of the metatarsal bone of the great toe (GT). The results showed that the mean values of VPT for both IF and GT were significantly higher in diabetics than in normal subjects. In both control and diabetic groups, the VPT values at GT only were elevated with increasing age. Furthermore, the mean VPTs at both IF and GT were related to the duration of illness and the severity of diabetes mellitus in the patient group. Eighty cases of diabetes mellitus received nerve stimulation tests including motor and sensory nerve conduction velocities of the upper and lower limbs. The results from these cases demonstrated good correlation between VPT and motor conduction velocity (MCV), but not between VPT and sensory conduction velocity (SCV). There was a negative correlation between VPT at IF and median MCV (p less than 0.0005) in the upper limbs, as well as VPT at GT and tibial MCV (p less than 0.0005) in the lower limbs. For clinical applications, VPT values seemed to be more sensitive than MCV in detecting neuropathic change in diabetic patients. Hence, impairment of vibratory perception can be taken as a subtle clinical sign of diabetic neuropathy, and measurement of VPT can be used as an index of a patient's current subclinical state.