Comparison of diabetic neuropathy symptom score and medial plantar sensory nerve conduction studies in diabetic patients showing normal routine nerve conduction studies

Objective: Diabetic Neuropathy Symptom (DNS) scoring and medial plantar NCS are useful methods for diagnosis of diabetic polyneuropathy (DPN). We evaluated the correlation between DNS score and medial plantar NCS in diabetic patients with a normal routine NCS. Method: Nineteen healthy subjects were included as a control group. Fifty patients with diabetes mellitus who were referred for the evaluation of DPN were recruited (35 asymptomatic and 15 symptomatic). Control subjects and diabetic patients over the age of 70 were excluded from this study. Results: Medial plantar nerve action potential (NAP) was recordable in all 19 control subjects and was not obtainable in 7 out of 15 symptomatic patients and in 5 out of 35 asymptomatic patients. The amplitudes of sural (Spearman r=-0.293, p=0.003) and medial plantar NAP (Spearman r=-0.215, p=0.03) correlated with DNS score. Conclusion: An abnormality finding in the medial plantar sensory nerve conduction study is a more sensitive indicator than sural nerve conduction study in the diagnosis of DPN and the medial plantar sensory nerve should be included in the evaluation of DPN in patients showing normal routine NCS.