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The aim of the study was to determine the progression of muscle weakness in long-term diabetes and its relation to the neuropathic condition. Thirty patients were recruited from a cohort of 92 diabetic patients who participated in a study on muscular function 6-8 years earlier. Nine subjects were nonneuropathic, 9 had asymptomatic neuropathy, and 12 had symptomatic neuropathy. Thirty matched control subjects who participated in the initial studies were also included. At follow-up, isokinetic dynamometry at the ankle, electrophysiological studies, vibratory perception thresholds, and clinical examination (neuropathy symptom score and neurological disability score [NDS]) were repeated. The annual decline of strength at the ankle was 0.7 ± 1.7% in control subjects, 0.9 ± 1.9% in nonneuropathic patients, 0.7 ± 3.1% in asymptomatic neuropathic patients, and 3.2 ± 2.3% in symptomatic neuropathic patients. In the symptomatic patients, the decline of muscle strength at the ankle was significant when compared with matched control subjects (P = 0.002) and with the other diabetic groups (P = 0.023). Also, the annual decline of muscle strength at the ankle was related to the combined score of all measures of neuropathy (r = -0.42, P = 0.03) and to the NDS (r = -0.52, P = 0.01). In patients with symptomatic diabetic neuropathy, weakness of ankle plantar and dorsal flexors is progressive and related to the severity of neuropathy. Diabetes 55:806-812, 2006
Diabetic polyneuropathy presents with sensory disturbances. Later on, motor disturbances can occur in more severe conditions, leading to distal weakness and atrophy of the muscles of the lower leg and foot. Accordingly, inability to walk on heels is used to identify diabetic subjects with this more severe degree of diabetic polyneuropathy (1). Using quantitative techniques, we observed that muscle strength is reduced at the ankle and knee and is related to the presence and severity of diabetic polyneuropathy in cross-sectional studies of type 1 and 2 diabetic patients (2,3). Also, the muscle weakness is associated with atrophy of striated muscle, probably due to insufficient reinnervation (4,5).
Duration of diabetes and poor metabolic control are well-known risk factors for development of diabetic polyneuropathy (6,7). In cross-sectional and prospective studies, a number of other risk factors have been identified, including hypertension, height, smoking, retinopathy, and microalbuminuria (8,9). In a follow-up...