Interdigital nerve conduction study of the foot for an early detection of diabetic sensory polyneuropathy

Objective: To report on the value of interdigital nerve (IDN) conduction study (NCS) of the foot for the recognition of diabetic sensory polyneuropathy with normal routine NCS and the nature of electrophysiological abnormality in early diabetic sensory polyneuropathy. Methods: The sensory nerve conductions in the two digital and 4 IDNs of the foot were obtained orthodromically using the near-nerve needle and signal averaging technique. Results: In 21 patients with diabetic sensory polyneuropathy with normal routine NCS, a definite neuropathy pattern (abnormalities in more than 3 of 6 tested nerves) was observed in 12 patients (57.1%). The most common abnormalities that were found were a low amplitude in the sensory compound nerve action potential and an absent potential, indicating that early diabetic sensory polyneuropathy is due to axonal degeneration. Conclusions: Interdigital NCS of the foot using near-nerve needle technique can identify neuropathy in diabetic sensory polyneuropathy with normal routine NCS. This technique offers a useful means of detecting nerve conduction abnormalities in the early stage of diabetic polyneuropathy.