ASSOCIATION OF MUSCLE STRENGTH AND ELECTROPHYSIOLOGICAL MEASURES OF REINNERVATION IN DIABETIC NEUROPATHY

Motor function was assessed in 34 non-insulin-dependent and 19 insulin -dependent diabetic patients with macroelectromyography and isokinetic dynamometry. Fiber density (FD) and the amplitude of the macro motor unit potential (macro MUP) of the anterior tibial and lateral vastus m uscles were obtained and maximal isokinetic strength of the ankle and knee extensors were determined. All patients underwent standardized cl inical examination including a neurological disability score (NDS), qu antitative sensory examination, and conventional motor nerve conductio n studies. The amplitude of the macro MUP and FD of the anterior tibia l muscle were increased in neuropathic patients without weakness (P < 0.05) and further increased in neuropathic patients with weakness (P < 0.05). The NDS was related to the FD and the amplitude of the macro M UP for the anterior tibial and lateral vastus muscle [r = 0.55-0.75 (P < 0.005)]. Muscle strength of ankle and knee extensors correlated wit h the FD [r = -0.69 (P < 0.0001) and r = -0.58 (P < 0.001), respective ly] and with the amplitude of the macro MUP of the two muscles [r = -0 .63 (P < 0.0001) and r = -0.37 (P < 0.05), respectively]. Our findings support the hypothesis that loss of muscle strength in diabetic patie nts is due to incomplete reinnervation following axonal loss. (C) 1998 John Wiley & Sons, Inc.