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June 2008

Carpal Tunnel Syndrome
Bernard F. Hearon, M.D.

Carpal tunnel syndrome occurs when the median nerve is compressed or pinched at the level of the wrist. The median nerve, which provides sensation to the thumb, index and middle fingers and powers most of the thumb muscles, passes through the carpal tunnel at the wrist. This tunnel is a non-yielding enclosure comprised of bone on three sides and a fibrous structure known as the transverse carpal ligament on the fourth or palmar side.

Entrapment of the median nerve within the carpal tunnel is the most common nerve entrapment syndrome and affects approximately 1% of the general population. Carpal tunnel syndrome is seen more frequently in patients with diabetes, obesity, inflammatory arthritis, kidney failure and hypothyroidism. Fifty percent of pregnant women will develop carpal tunnel syndrome during pregnancy due to fluid imbalance and peripheral swelling. Their symptoms usually resolve after delivery.

Though carpal tunnel syndrome has been associated with certain occupations, there is no scientific evidence to show specific occupational stresses (such as typing or computer data entry) directly cause carpal tunnel syndrome. Nevertheless, the repetitive hand and wrist stress associated with many jobs is believed to aggravate the symptoms of carpal tunnel syndrome. Thus, carpal tunnel syndrome remains a work compensable diagnosis in Kansas and in other states.

Recent review of the available medical evidence indicates that carpal tunnel syndrome is caused by structural, genetic and biological factors (ref. 2). For instance, identical twins are observed to have carpal tunnel syndrome more often than non-identical twins. Also, women, as they may have relatively smaller carpal canals, are affected by carpal tunnel syndrome three times as often as men.

In patients with carpal tunnel syndrome, increased pressure within the carpal canal compresses the median nerve and decreases blood flow to the segment of the nerve within the enclosed tunnel. Without adequate blood flow, nerve signals or impulses can no longer be effectively conducted through this portion of the nerve. The result is numbness and tingling of the thumb, index, middle and sometimes ring fingers, particularly with grasping activities during the day and night time numbness which often awakens patients from sleep. Patients will shake the numb hand to restore blood flow to the nerve and, in turn, sensation to the hand.

The diagnosis of carpal tunnel syndrome is a clinical diagnosis based on patient history of hand numbness and tingling, sometimes hand and/or forearm pain and specific findings on physical examination. The physician will often be able to reproduce the numbness by compressing the median nerve at the wrist or by palmar flexing the wrist. The diagnosis may be confirmed by nerve conduction test which determines the speed of median nerve impulses and by electromyogram which assesses the muscles supplied by the nerve. The nerve testing also quantifies the severity of the carpal tunnel syndrome.

Nonoperative treatment for carpal tunnel syndrome includes use of removable short-arm splint at night to control nocturnal symptoms. Steroid injection into the carpal canal may provide temporary relief of symptoms, but rarely will relieve symptoms for a year or more. There is no clear scientific evidence to support the use of other nonoperative treatments such as oral steroids, non-steroidal anti-inflammatory medicines, diuretics, vitamin B6, magnets, laser light therapy or chiropractic therapy.

The most reliable method to eliminate pressure on the median nerve within the carpal canal in patients with carpal tunnel syndrome is to surgically divide the transverse carpal ligament in the palm. This simple operation opens the carpal tunnel and improves blood flow to the median nerve. In cases of severe, long-standing nerve compression, carpal tunnel release permits the damaged portion of the median nerve to regrow, possibly restoring hand sensation. Most surgeons prefer standard open carpal tunnel release over other surgical methods, because the open technique minimizes surgical risk and maximizes the ability to visualize and decompress the median nerve.

Figure 1 Palmar Incision	Figure 2 Transverse Carpal Ligament
Figure 3 Median Nerve	Figure 4 Closed Incision

Carpal tunnel release is performed on an outpatient basis. Patients begin finger motion in the recovery room immediately after surgery. Wrist motion is started three days after surgery. Sutures are removed during office visit two weeks after surgery when scar massage is initiated. As noted in recent journal article (ref. 3), supervised physical therapy following carpal tunnel release is rarely required. Palmar soreness near the incision is expected for 4 to 6 weeks after surgery.

For those with mild or moderate carpal tunnel syndrome, carpal tunnel release is a permanent solution. However, for patients with severe nerve compression preoperatively, carpal tunnel release may improve but not eliminate symptoms due to advanced nerve damage. Patient satisfaction with the outcome of carpal tunnel release may be predicted on the basis of patient’s coping skills as well as on the severity of nerve compression (ref. 1).

In summary, carpal tunnel syndrome is common in the adult population. The diagnosis is made on the basis of history and physical examination, but should be confirmed by nerve testing which quantifies disease severity. Other studies such as radiographs and MRI are not necessary for diagnosis.

Though splinting and injections may help somewhat, most nonoperative treatments for carpal tunnel syndrome are not effective and are wasteful of health care resources. Open carpal tunnel release is indicated for patients with significant symptoms of carpal tunnel syndrome. Patients should consider surgery sooner rather than later, because those with mild to moderate nerve compression can expect better surgical outcomes than those with severe nerve compression.

Want more information online? Go to www.assh.org or www.orthoinfo.aaos.org and click on carpal tunnel syndrome.

References

1. Lozano-Caldron SA, Paiva A, Ring D. Patient Satisfaction After Open Carpal Tunnel Release Correlates With Depression. J Hand Surg, 33-A: 303-307, March 2008.

2. Lozano-Caldron SA, Anthony S, Ring D. The Quality and Strength of Evidence for Etiology: Example of Carpal Tunnel Syndrome. J Hand Surg, 33-A: 525-538, April 2008.

3. Pomerance J, Fine I. Outcomes of Carpal Tunnel Surgery With and Without Supervised Postoperative Therapy. J Hand Surg, 32-A: 1159-1163, October 2007.