Evaluation of medial plantar, dorsal sural nerve conduction and sural/radial amplitude ratio in prediabetic patients.

BACKGROUND AND PURPOSE: Distal sensory polyneuropathy (DSPN) is a common complication of Diabetes Mellitus (DM). Patients often experience disturbing neuropathic symptoms such as numbness and burning. These symptoms can also be seen in prediabetic patients who do not meet the diagnostic criteria for DM. The sural nerve responses are evaluated as standard in electrophysiologic technique. However, the sural nerve may not always show abnormalities in those with mild neuropathy. Therefore, different nerves can be studied to detect mild neuropathy. Our study aimed to investigate both the superiority of electrophysiological tests evaluating mild neuropathy over each other and the sensitivity of these tests in patients with preDM. To do that, it focused on studying medial plantar, dorsal sural and sural/ radial amplitude ratio (SRAR) in prediabetic or DM patients.

METHODS: The study employed patients with prediabetes and DM. Our study included 92 (65 female, 27 male) patients. The neuropathic symptoms of the patients were evaluated using the Self-Leeds Assessment of Neuropathic Symptoms and Sign (LANSS) pain scale. In addition to standard electrophysiological studies, nerve conduction studies were conducted on dorsal sural, medial plantar and radial nerve. SNAP (sensory nerve action potential) amplitudes of prediabetic patients without neuropathic symptoms are compared with healthy controls.

RESULTS: Although the mean amplitude of dorsal sural and medial plantar responses in the preDM patient group with high LANSS scores is at the lower limit of normal, it was significantly lower than those with low LANSS score. There was no significant difference in the SRAR rates between the two groups. Among the prediabetic patients with neuropathic symptoms, 13 (56%) showed below normal dorsal sural responses and 16 (69%) exhibited below normal medial plantar responses.

CONCLUSION: The findings of our study show that dorsal sural and medial plantar responses may be affected in prediabetic patients with neuropathic complaints, even if sural nerve conduction is normal. Medial plantar nerve SNAP found to be more sensitive. In contrast, SRAR was evaluated as having a low contribution compared to dorsal sural and medial plantar responses in detecting a mild polyneuropathy. It is important to look for polyneuropathy in prediabetic patients with sensitive electrophysiological methods.