Background: Asymptomatic median mononeuropathy (AMM) and diabetic polyneuropathy (DPN) often coexist and can be difficult to distinguish electrophysiologically. Moreover, the potential association between AMM and DPN has not been extensively evaluated.
Objective: We investigated the relation between AMM and DPN severity in consecutive diabetic patients.
Methods: The non-dominant limb was studied electrophysiologically in 100 consecutive diabetic patients with no symptoms of carpal tunnel syndrome on the non-dominant side. AMM was diagnosed based on previously validated electrophysiological criteria. DPN severity was graded according to the Michigan diabetic neuropathy score.
Results: AMM was discovered in 28% of the study population (Adjusted Wald 95% CI: 20%-37%). It was more common in women, displayed a tendency of being more common in patients over 50 years old and correlated with the severity of DPN and the number of abnormal nerves on nerve conduction studies. It was present in 18.1% of patients without evidence of DPN. No correlation was found with the duration and type of diabetes. In multivariate logistic regression models increasing severity of DPN was independently associated with the presence AMM (Wald test=10.557, df=3, p=0.014). Patients with DPN stage III and IV had a five-fold (OR=5.06, 95% CI=1.49-17.19) and a four-fold (OR=4.50, 95% CI=1.15-17.65) respectively increased likelihood to present with AMM in comparison to DPN stage I (reference group).
Conclusions: Our results confirmed the high incidence of AMM in diabetic patients. AMM was present in a significant number of patients in the absence of DPN and the likelihood of AMM detection increased with increasing severity of DPN.