Evidence of improvement in distal conduction of ulnar nerve sensory fibers after carpal tunnel release.

OBJECTIVE: The aim of this study was to verify any effect of carpal tunnel release (CTR) on distal ulnar nerve conduction findings, using the database of a previous study performed to establish a protocol for CTR outcome.

METHODS: The motor and sensory ulnar distal conduction findings of 251 consecutive hands belonging to 217 patients (175 women and 42 men; mean age, 55.6 years) with idiopathic carpal tunnel syndrome (CTS) were reanalyzed before and 1 and 6 months after CTR.

RESULTS: Before surgery, 115 hands (45.8%) showed reduction of ulnar nerve sensory action potential (SAP) amplitude; this number was reduced significantly to 85 (33.9%) after CTR. The SAP amplitude and sensory conduction velocity values of the ulnar nerve showed significant improvement 1 month after CTR; SAP amplitude values showed further significant improvement 6 months after CTR. Patients' ages and occupations were independent predictors of reduced baseline SAP amplitudes of the ulnar nerve in CTS.

CONCLUSION: These results demonstrate an improvement in conduction values in sensory ulnar fibers in a percentage of patients with CTS after CTR, providing further support for the conclusion that in CTS ulnar fibers may be subject to compressive forces in the Guyon canal as a consequence of high pressure in the carpal tunnel.