Asymptomatic Median Neuropathy in Patients with Diabetic Polyneuropathy

Abstract

Aim: This study aims to investigate whether asymptomatic median neuropathy (AMN) in patients with diabetic peripheral polyneuropathy (DPNP) is a result of polyneuropathic involvement of median nerve (MN) or its true entrapment. Subjects and Methods: We determined the grades of the Michigan severity scale and the rates of peripheral nerve conduction abnormalities in study subgroups, including patients with carpal tunnel syndrome (CTS), AMN, and normal MN conductions to highlight if the severity of polyneuropathic involvement was different between them. In addition, the results of conventional and comparative nerve conduction studies (NCSs) were compared between these study subgroups. Results: Distributions of Michigan grades and rates of abnormalities in peroneal and sural NCSs were similar between the subgroups (P > 0.05 for all analyses). Abnormality rates of ulnar NCSs were higher in the AMN group than in the other groups, whereas those of comparative transcarpal NCSs were higher in the CTS group. The mean distal sensory latency (DSL) and motor latency (DML) of MN were longer, sensory conduction velocity (SCV) was slower in the CTS group than AMN group, whereas MN motor conduction velocity (MCV) was slower, UN DSL was longer, SCV was slower, SNAP amplitude was smaller, DML was longer, and MCV were slower in the AMN group (P < 0.05 for all analyses). Discussion: Our findings reveal that grade of polyneuropathic involvement is more prominent in AMN, whereas transcarpal MN conduction delay is greater in CTS. The results of the study suggest that the prominence of polyneuropathic impairment in addition to a lesser degree of MN sheet compression obscures the clinical signs in patients with diabetes with AMN.