Axonal dysfunction in the neuropathy of diabetes mellitus: a quantitative electrophysiological study.

The extent of axonal dysfunction in a group of patients with diabetes mellitus has been investigated using recently introduced quantitative techniques of electromyography. In 40 diabetic patients, estimates of motor unit numbers in the extensor digitorum brevis muscles and measurements of the parameters of electrically evoked motor unit potentials therein are presented, along with significant correlations between these parameters and motor nerve conduction velocities and distal motor latencies in the lateral popliteal nerves. The results indicate that axonal dysfunction and concomitant collateral reinnervation are prominent and integral features of the neuropathy of diabetes mellitus. Axonal dysfunction is present in proportion to and parallels the severity of the demyelinative lesion. It is also extensive in patients without clinical evidence of neuropathy in whom the accompanying collateral reinnervation is of sufficient magnitude to mask the clinical signs of motor involvement.