Objective: Carpal tunnel syndrome (CTS) and diabetic polyneuropathy (DPN) are common conditions in patients with diabetes and therefore frequently occur concomitantly. Diagnosis of CTS in patients with DPN is important, as therapeutic interventions directed toward relief of CTS may be effective irrespective of diffuse neuropathy. The prevalence of clinical CTS and the most efficient electrodiagnostic discriminators of CTS from diffuse neuropathy are uncertain.
Research design and methods: A total of 478 subjects, including reference subjects (without diabetes and without neuropathy), nonneuropathic subjects with diabetes, and diabetic subjects with mild, moderate, and severe neuropathy, were evaluated in a cross-sectional design for clinical features of CTS. In the ascertainment of the cohort, a clinical stratification method was used to ensure a broad spectrum of neuropathy severity. All subjects underwent nerve conduction study determinations of median, ulnar, and sural nerve parameters.
Results: The prevalence of clinical CTS was 2% in the reference population, 14% in diabetic subjects without DPN, and 30% in those with DPN. Multiple linear regression analysis revealed that mean electrodiagnostic parameters are not significant predictors of clinical CTS in patients with diabetes. Generally, the parameters worsened with severity of neuropathy, but none reliably distinguished diabetic patients with and without CTS.
Conclusions: Given the high prevalence of CTS in patients with DPN and that electrodiagnostic criteria cannot distinguish those with clinical CTS, it is recommended that therapeutic decisions for CTS be made independently of electrodiagnostic findings.