Reduced longitudinal excursion of the median nerve in carpal tunnel syndrome

Objective: To determine if longitudinal excursion of the median nerve is reduced in patients with carpal tunnel syndrome (CTS). Design: Case-control study. Setting: University human movement laboratory. Participants: Nineteen patients with CTS (8 men, 11 women; mean age, 57 +/- 15y), and 37 healthy controls (8 men, 29 women; mean age, 48 +/- 10y). Interventions: Not applicable. Main Outcome Measures: Longitudinal excursion of the median nerve, and the ratio of nerve to flexor digitorum superficialis tendon excursion at the carpal tunnel evoked by finger extension. Measurements were taken using a validated Doppler ultrasound technique, and tests were conducted with the elbow positioned in extension and flexion. Results: Mean longitudinal excursion of the median nerve was significantly greater in controls (11.2 2.8mm) than patients (8.3- 2.6mm) with the elbow extended (P=.013), but not with the elbow flexed (controls, 12.5 +/- 2.5mm; patients, 10.2 +/- 3.1mm; P=.089). Mean nerve/tendon excursion ratios were significantly greater in controls (.32 +/-.07) than patients (.23 +/-.06), with the elbow extended (P<.001), and flexed (controls,.36 +/-.06; patients,.28 +/-.10; P=.019). Discriminant analysis identified that 11 (58%) of the 19 patients and 3 (8%) of the 37 controls showed a nerve/ tendon excursion ratio of .25 or less when tested with the elbow in extension. Conclusions: Reduced longitudinal excursion of the median nerve at the carpal tunnel was identified in a substantial proportion of patients with CTS. Further studies are merited to determine if reduced median nerve excursion at the carpal tunnel is clinically relevant in CTS, and can be influenced by movement-based interventions.