Carpal tunnel syndrome

Carpal tunnel syndrome (CTS) or Median Neuropathy at the Wrist occurs when the median nerve becomes pressed or squeezed as it travels from the forearm (antebrachium) through the wrist into the hand. The median nerve controls sensations to the palm side (anterior) of the thumb and fingers (although not the little finger), as well as impulses to some small muscles in the hand that allow the fingers and thumb to move.

On the anterior side of the wrist is a sheath of connective tissue that forms a transverse carpal ligament, the flexor retinaculum. It is attached, medially, to the pisiform and the hamulus of the hamate bone; laterally, to the tubercle of the scaphoid, and to the medial part of the volar surface and the ridge of the trapezium. This ligament is superficial to the flexor tendons for the Phalanges (fingers). The carpal tunnel is the space posterior to (deep to) the flexor retinaculum and anterior to (superficial to) the carpal bones, through which the tendons slide during hand and particularly during finger movement. These tendons include the flexor digitorum profundi, and flexor digitorum superficiali groups, as well as the flexor pollicis longus. The median nerve also travels through the carpal tunnel.

If an inflammation exists which causes any of the structures associated with the carpal tunnel to swell appreciably, or if the size of the canal is reduced (such as when bending the wrist at a 90 degree angle, for instance), the median nerve can become compressed causing symptoms of pain, paresthesias, and muscle weakness in the forearm and hand.

In terms of treatment, the underlying cause can offer some guidance. Hypothyroidism for instance is implicated in some cases when the reduced thyroid hormone levels cause synovial swelling. Treatment of the root cause disorder can offer relief from symptoms. Other treatments for CTS include anti-inflammatory medications (steroidal and non-steroidal), restriction/limitation of hand/wrist motion, and "carpal tunnel release" surgery. In carpal tunnel release surgery a surgeon physically severs the flexor retinaculum ligament to release the pressure on the median nerve.