Tibial nerve axonal excitability in type 1 diabetes mellitus.

Introduction: The aim of this study was to determine alterations in axonal excitability in tibial nerve as compared with median nerve axonal excitability in patients with diabetic polyneuropathy.

Methods: Six patients with diabetic polyneuropathy and 10 patients with diabetes mellitus without polyneuropathy were enrolled.

Results: Compared with diabetic patients without polyneuropathy, the tibial nerve strength-duration time constant was significantly longer and supernormality was lower in those with polyneuropathy. Threshold electrotonus studies showed abnormalities in patients with diabetic polyneuropathy, in which smaller threshold changes from long-depolarizing and hyperpolarizing conditioning, termed "fanning-in," were found.

Discussion: This study confirms that axonal excitability is significantly altered in the tibial nerve of patients with diabetic polyneuropathy. Evaluating the axonal excitability of the median and tibial nerves may reveal the presence of length-dependent polyneuropathy at an early stage. Muscle Nerve 59:76-81, 2019.