Study of carpal tunnel syndrome in diabetic polyneuropathy with comparison of inching method and second lumbrical-interossei test

Since diabetic generalized neuropathy affects peripheral nerves, the diagnosis of carpal tunnel syndrome (CTS) with conventional electrodiagnostic techniques (EDX) [onset latency of median sensory nerve action potential (SNAP) or distal latency of median compound muscle action potential (CMAP)] is controversial. The aim of this study is to investigate the diagnostic values of two other techniques including inching method and second lumbrical-interossei test in patients with diabetic polyneuropathy (DPN) as well as signs or symptoms of CTS. Fifteen patients (30 hands) with definite diagnosis of generalized peripheral neuropathy secondary to diabetes who developed signs and symptoms of CTS were participated. For diagnosis of CTS, sensory and motor median distal latencies were considered by nerve conduction study. In the next step, inching method and second lumbrical-interossei test were performed for all hands. Finally, sensitivity and specificity of two tests were calculated. Mean age of participants was 53.87 ± 11.53 years. The sensitivity and specificity of inching method in this study were 95.65% and 85.71%, respectively, and for the second lumbrical-interossei test, they were 73.91% and 71.42%, respectively. Inching method was more sensitive and specific than second lumbrical-interossei test in diagnosis of CTS among patients with diabetic peripheral neuropathy. Moreover, the sensitivity of inching method was greater than specificity.