Accelerated atrophy of lower leg and foot muscles--a follow-up study of long-term diabetic polyneuropathy using magnetic resonance imaging (MRI).

AIMS/HYPOTHESIS: The aim of the study was to determine the loss of muscle volume in the lower leg and foot in long-term diabetic patients in relation to the presence of neuropathy.
METHODS: We re-examined 26 type 1 diabetic patients who had participated in magnetic resonance imaging (MRI) studies on muscle volume in the lower leg and foot 9 to 12 years earlier. Re-examination involved MRI, isokinetic dynamometry, clinical examination, electrophysiological studies and quantitative sensory examinations.
RESULTS: Annual loss of muscle volume of ankle dorsal and plantar flexors was 4.5 (5.5-3.9)% (median [range]) and 5.0 (7.0-4.2)% in neuropathic patients, 1.9 (3.2-1.0)% and 1.8 (2.6-1.3)% in non-neuropathic patients, and 1.7 (2.8-0.8)% and 1.8 (2.4-0.8)% in controls, respectively (p < 0.01). Annual change of volume and strength correlated for ankle dorsal flexors (r (s) = 0.73, p < 0.01) and for ankle plantar flexors (r (s) = 0.63, p < 0.05) in diabetic patients. In addition, annual change of muscle volume for dorsal and plantar flexors was related to the combined score of all measures of neuropathy (r (s) = -0.68, p < 0.02 and r (s) = -0.73, p < 0.01, respectively). Foot muscle volume declined annually by 3.0 (3.4-1.0)% in neuropathic patients and by 1.1 (4.0-0.2)% in non-neuropathic patients, both values being significantly different from controls (0.2 [-2.5 to 2.4]%). Loss of foot muscle volume was related to severity of neuropathy assessed at clinical evaluation (r (s) = -0.6, p < 0.05). CONCLUSIONS/
INTERPRETATION: Muscular atrophy in long-term diabetic neuropathy occurs early in the feet, progresses steadily in the lower legs, relates to severity of neuropathy and leads to weakness at the ankle.