Carpal tunnel syndrome is a well established symptom complex resulting from median nerve compression at the wrist. Referring to FIGS. 1 and 2, the carpal tunnel T is located on the palmar aspect of the wrist (carpus or wrist bones) (see aspect of FIG. 1) between the distal wrist flexion crease 14 and, roughly, the center of the ulnar border of the thenar muscle mass 16. The anatomy of the carpal tunnel and its contents is shown in relation to the surface structures in the section of FIG. 2. The median nerve 20 is superficial on the radial aspect of the flexor tendons 24 and branches, just distally to the distal border of the transverse carpal ligament L. Those familiar with anatomy will know that four superficial flexors, four deep flexors, the flexor pollicis longus and the median nerve normally travel through this tunnel.
The boundaries of the carpal tunnel are inelastic on three sides (see bones B in FIG. 2). The dorsal radial and ulnar borders form the U-shaped configuration. The fourth side, palmar side is formed by the transverse carpal ligament.
Any condition, systemic or local, that reduces the normal available cross-sectional area of the carpal tunnel--either by increasing the volume of contents or by decreasing the diameter of the tunnel--causes local constriction of the median nerve (the structure most sensitive to compression in the tunnel). The most common symptoms are those of sensory abnormalities in the median nerve distribution of the hand. See M, FIG. 1. These include hyperesthesia (acute irritating hypersensitivity), paresthesia (burning, tingling "pins and needles" sensation), hypoesthesia (decreased sensitivity) and, occasionally, pain and numbness.
Surgery is indicated for long-standing cases of carpal tunnel syndrome refracting to consensitive care, especially those with obvious muscle atrophy of the median enervated thenar muscles, for relief of the symptoms. The purpose of the surgery is two-fold: (1) to release the pressure on the median nerve and (2) to diagnose and treat the pathology responsible for nerve compression.