Estimates of functional motor axon loss in diabetics

Estimates of the number of motor units in extensor digitorum brevis (EDB) and in the thenar muscles were made electrophysiologically in a group of 66 diabetic subjects. Loss of motor units was common in those with no clinical evidence of neuropathy and was most severe in EDB. The clinical form of the neuropathy was a poor guide to the severity of EDB or thenar motor unit loss. Motor unit losses in diabetics 60 years of age or over did not differ from those found in many control subjects of equivalent age. The finding of motor unit loss, abnormal digital sensory potentials and motor conduction velocity slowing in diabetics without a neuropathy and in unaffected limbs of those with a neuropathy, pointed to a general metabolic disturbance of diabetic peripheral nerves. This may have made diabetic nerves more liable to nerve entrapment and probably accounted for the large number of subjects with local neuropathies, particularly of the median nerve in the region of the carpal tunnel.