Role of interdigital sensory nerve conduction study as a noninvasive approach for early diagnosis of diabetic peripheral neuropathy

Diabetes mellitus is amongst the most common causes of polyneuropathy worldwide that can eventually terminate to irreversible complications. The remarkable impact of diabetic polyneuropathy as a debilitating condition on the healthcare system and total costs of diabetes care is undeniable. Despite the existence of numerous diagnostic tools such as routine electrophysiologic procedures, its early detection is challenging. This study designed to compare more distal techniques of electrodiagnostic testing, including interdigital sensory nerve conduction studies (NCSs), with conventional approaches and to investigate its role in confirming the early stages of polyneuropathy. This cross-sectional study was performed in the Physical Medicine and Rehabilitation Department of Hazrat Fatemeh Reconstruction Surgery Hospital. Thirty one symptomatic diabetic outpatients and 23 asymptomatic nondiabetic subjects included in our study. We performed nerve conduction studies on five sensory nerves consist of the dorsal sural nerve, medial plantar nerve, digital branches of the interdigital nerves to toes I, II, and III (as a new antidromic technique). In this study, all techniques applied with a surface stimulator and pick-up electrodes. In the group of patients, 9 (29%) and 22 (71%) subjects had impaired and normal routine NCSs, respectively. Interestingly, the results of interdigital nerve studies were abnormal in the 17 out of 22 patients with normal routine NCSs. Also, 11 and 13 subjects had impaired medial plantar nerve and dorsal sural nerve conduction studies, respectively. Accordingly, with this new method, the prevalence of detectable diabetic neuropathy increased from 46% to 83%. We conducted this study intending to demonstrate the application of a new technique for early diagnosis of diabetic polyneuropathy, especially in the presymptomatic and subclinical neuropathies. The digital sensory branches of IDNs known as the most distal sensory nerves, which can be easily evaluated with new antidromic SNAP technique. Our method is simple, non-invasive, suitable, sensitive, and reproducible. There is no need to needle electrode or averaging technique to record an appropriate amplitude of IDN. Thus, it is recommended as a convenient electrophysiological option for early diagnosis of DPN.