Diabetic neuropathy is one of the most common complications of diabetes mellitus. Hence the early detection and treatment is important. It is known that the electrophysiologic study is one of the most sensitive tests in the diagnosis of diabetic neuropathy. The purpose of this study was to find out whether the somatosensory evoked potential (SEP) study of median and posterior tibial nerve can give additional information to conventional nerve conduction study and in which conditions the SEP study is useful in diabetic neuropathy.

The medical and electromyographic records of 57 patients referred to the electromyographic laboratory of Seoul National University Hospital were reviewed. Inclusion criteria were patients 1) who had history of diabetes mellitus, 2) who had no other systemic diseases that may cause polyneuropathy, 3) who had undertaken the motor and sensory nerve conduction study of median, ulnar and tibial nerve of both sides, 4) who had undertaken the SEP study of median and posterior nerve of both sides. The number of patients with abnormal median nerve SEP response was 29.8% (17/57), and the number of patients with abnormal posterior tibial nerve SEP was 70.2% (40/57). All the patients with abnormal SEP response in median nerve showed abnormal SEP response in posterior tibial nerve. The more severe the results of the nerve conduction study, the higher the percentage of abnormality in posterior tibial SEP response. Among various electrodiagnostic parameters, the percentage of abnormality of posterior tibial nerve SEP ranked second (70.2%), next to tibial nerve conduction study (77.2%). But considering the combinations of various electrodiagnostic parameters, the posterior tibial nerve SEP study had little benefit to nerve conduction study. Of 7 patients with normal nerve conduction study results, only one patient showed abnormal SEP response. Of 17 patients with normal SEP response, 11 patients showed abnormal nerve conduction study results. The conclusion was that the SEP study does not give additional information to nerve conduction study.