Restricted motion of the median nerve in carpal tunnel syndrome.

Motion of the median nerve was compared on an axial ultrasonographic image in the mid-carpal tunnel in 30 wrists of 15 women with bilateral idiopathic carpal tunnel syndrome and 30 wrists of 15 healthy women. During passive flexion and extension of the index finger, the control wrists had transverse sliding of the nerve beneath the flexor retinaculum (1.75 +/- 0.49 mm), which was regarded as a physiological phenomenon. In contrast, the wrists of patients with carpal tunnel syndrome had significantly less sliding (0.37 +/- 0.34 mm; P = 0.0001), which indicates that physiological motion of the nerve is restricted. This decrease in nerve mobility may be of significance in the pathophysiology of carpal tunnel syndrome.