Muscle Modification in Asymptomatic Diabetic Neuropathy: a Surface Electromyographic Study

In 24 non insulin-dependent diabetic patients [NIDDM-12 with (ND+) and 12 without (ND-) asymptomatic polyneuropathy] in stable metabolic control, and in 12 age-matched controls (C), we studied the functional properties of tibialis anterior muscle (TA) through an electrically elicited contraction. We recorded the surface EMG signal and analysed the median frequency of power spectrum (MDF), the average rectified value of amplitude (ARV) and the muscle fibers conduction velocity (CV). At the beginning MDF, ARV and CV were significantly decreased in ND+ compared both to NDand controls. After 23 and 43 sec from the beginning of the stimulation a statistically significant decrease in CV was observed in ND+ compared to NDand controls (-26% and -49% in ND+, -9% and 28% in ND-, -12% and -30% in C p<0.01). No significant differences emerged as regard MDF and ARV among three groups, either after 23 and 43 sec of electrical stimulation. Our main findings are consistent with a decrease in mean size of muscle fibers in ND+ respect to NDand controls. This data suggest a muscle fibers hypotrophy even in non denervated ones. Moreover we can suppose a shift of fiber composition toward the type II fibers in asymptomatic neuropathic diabetic patients. In conclusion, we observed a myopathic involvement in TA of asymptomatic NIDDM patients. So, it seems very important to early detect muscle function impairment in these patients in order to advise them appropriate rehabilitative program.