Effects of chronic median nerve compression at the wrist on sensation and manual skills.

The aim of this study was to analyse the functional impairments caused by chronic median nerve compression at the wrist on hand sensation and manual skill. Hand function was assessed in 11 patients (8 women and 3 men) with severe carpal tunnel syndrome (CTS) and compared with that of an age- and sex-matched control group. Apart from CTS, the subjects were healthy and the electrodiagnostic examination was normal. The pressure and vibration detection thresholds of the index finger were partially impaired and statistically different (P<0.05) when compared with controls, suggesting a reduction of tactile acuity in the territory of the median nerve. The thermal thresholds were identical in both groups, suggesting that the small-diameter fibres were not affected. When a small object was lifted and positioned in space, the coordination between the grip force and the vertical lifting force did not seem to be affected in our patients. They were able to modify their grip force according to the friction between the fingertips and the object, i.e. the more slippery the object, the higher the grip force. The unimanual Purdue Pegboard subtest results suggest that digital dexterity was also not significantly perturbed in our sample of CTS patients when compared with controls. Despite the severe abnormalities of median nerve conduction, our results suggest that chronic median nerve compression occurring in CTS induces partial impairment of tactile sensibility with minor impact on grasp force regulation and digital dexterity.