Correlation between nerve conduction study (NCS) and clinical improvement in carpal tunnel syndrome (CTS)

Abstract

Objective : To determine the correlation between the changing of parameters of nerve conduction study (NCS) and clinical symptoms in carpal tunnel syndrome (CTS) patients after conservative treatments.

Design : Retrospective study.

Setting : Electrodiagnosis Laboratory Unit, the Department of Rehabilitation Medicine, King Chulalongkorn Memorial Hospital.

Methods : All NCS reports from 1 Jan 2006 to 31 Dec 2008 were reviewed and studies that met the inclusion criteria were recruited into the study. All parameters of NCS included distal sensory latency (DSL), sensory nerve action potential (SNAP) amplitude, distal motor latency (DML) and compound muscle action potential (CMAP) amplitude of median nerve that were tested at both pre- and post-treatments were recorded. The baseline characteristics and clinical responses to the treatments were reviewed and recorded from medical records (OPD card). Correlation coefficients were analyzed by SPSS program by using Spearman’s rank correlation coefficient.

Results : Reports of 59 hands of 41 CTS patients were recruited into the study. Fifty-six percent of the hands revealed a good improvement of symptoms after treatments. Correlation coefficients of the change in each NCS parameter (DSL, SNAP amplitude, DML and CMAP amplitude) and clinical symptoms were -0.337, 0.345, -0.228 and -0.004, respectively (p-value = 0.009, 0.007, 0.082 and 0.974).

Conclusion : The improvement of clinical symptoms was significantly correlated with the change of sensory nerve conduction study including both of DSL and SNAP amplitude at a weak level (r < 0.4), while motor nerve conduction study did not show a significant correlation (neither DML nor CMAP amplitude).