Carpal Tunnel Syndrome In Patients With Diabetic Polyneuropathy

Abstract

Diagnosis of carpal tunnel syndrome (CTS) in patients with diabetic polyneuropathy (DPN) is important as therapeutic interventions directed towards relief of CTS may be effective irrespective of DPN. The frequency of clinical CTS and the best electrodiagnostic discriminator of CTS from diffuse neuropathy are uncertain. 478 subjects including reference, non‐neuropathic subjects with diabetes mellitus (DM), and diabetic patients with mild, moderate and severe neuropathy were evaluated for clinical features of CTS. All subjects had routine determinations of median nerve distal motor and sensory latencies, sensory and motor potential amplitudes and sensory conduction velocities. Other parameters tested were: ratios of median to ulnar nerve distal motor and sensory latencies, distal motor and sensory amplitudes, and distal conduction velocities. Similar median to sural nerve ratios for sensory latencies, amplitudes and conduction velocities were determined as were ratios of median nerve motor amplitudes and latencies to sural nerve parameters. Segmental median sensory nerve conduction velocities were evaluated. The frequency of clinical CTS was 2% in the reference population, 14% in diabetic patients without DPN, and 30% in those with DPN. We did not find any reliable electrodiagnostic discriminator for CTS in patients with DM +/− DPN. Some of the parameters worsened with severity of neuropathy, but none reliably distinguished diabetic patients with and without CTS. Given that CTS is frequent in patients with DPN, but electrodiagnostic criteria cannot distinguish those with clinical CTS, a trial of therapy may be indicated in these patients regardless of the electrodiagnostic findings.