[Electrophysiological analysis of diabetic polyneuropathy with microneuronography]

We recorded median nerve action potentials in 40 healthy individuals and 40 patients with type II diabetes mellitus by means of microneurography. The latter group included 20 patients complicated by dysesthesia of distal extremities (mean diabetic history: 12.4 years), and another 20 patients without dysesthesia (mean diabetic history; 5.5 years). Mean age of each group was about 60 years old and had no significant difference among three groups. Patients and healthy controls gave an informed consent for participation in this study. A tungsten microelectrode with a tip diameter of about 1 micron was inserted percutaneously into the median nerve trunk at elbow without anesthesia. With supramaximal electric stimulation on the median nerve at wrist, the largest compound nerve action potential was recorded. In healthy controls the median nerve action potential showed a large triphasic wave (positive-negative-positive, 400 microV in average amplitude) followed by small multiphasic waves. In diabetics maximal conduction velocity (NCV) and amplitude of this triphasic wave (Amp) were decreased and multiphasic waves became more prominent. Reproducibility of potentials in the same subject was acceptable. The differences among three groups were most conspicuous in Amp, and the amplitude of the multiphasic wave was increased in diabetic patients with dysesthesia. Thus, the diminution of Amp appeared to be associated with temporal dispersion due to segmental demyelination. In diabetic polyneuropathy NCV and Amp decreased along with the disease progression; in patients with advanced disease and subjective symptoms, small Amp and prominent multiphasic waves became apparent.(ABSTRACT TRUNCATED AT 250 WORDS)