Electrophysiological investigations in diabetic patients: Root stimulation and autonomic investigations

Introduction: The aim of the study is to search proximal nerve involvement by using proximal root stimulation and possible autonomic neuropathy in type 2 diabetic patients with and without distal symmetric sensorimotor polyneuropathy (DSPN). Patients and Methods: Forty patients with type 2 diabetes and ten volunteers who had no history of diabetes and neuropathy were included. Diabetic patients were equally distributed into two groups according to nerve conduction studies (NCSs): First group comprised of with electrophysiologically confirmed DSPN and second group with normal NCSs. Electrophysiological tests included motor and sensory nerve conduction, needle electromyography, F-response, H-reflex, R-R interval, and sympathetic skin responses (SSRs) studies as well as lumbar root stimulation and cauda equina motor conduction time (CEMCT) calculation. Results: The patients with DSPN had significantly longer F-response latencies and had no H-reflex while H-reflex was observed in 35% of the patients in second group. In the first group, SSRs could not be obtained from both upper and lower limbs in 45% of the patients; however, in the second group, they were absent only in 10% of patients in lower limbs. R-R interval variability was significantly lower in both diabetic groups than volunteers. When compared to the volunteers, cauda equine motor conduction time was significantly prolonged in all diabetic patients, but there was no significant difference between the patient groups. Conclusions: CEMCT prolongation, absence of H-reflex, and decreased R-R interval abnormalities indicating dysautonomia were the most important findings of our study. These results show that early electrophysiological examinations using these methods are important in diabetic patients without polyneuropathy.