Carpal Tunnel Syndrome

The most common of the nerve entrapment syndromes, carpal tunnel syndrome results from compression of the median nerve at the wrist, within the carpal tunnel. This nerve passes through, along with blood vessels and flexor tendons, to the fingers and thumb. Compression neuropathy causes sensory and motor changes in the median distribution of the hand.
Carpal tunnel syndrome usually occurs in women between ages 30 and 60 and poses a serious occupational health problem. Assembly-line workers and packers, secretary-typists, and persons who repeatedly use poorly designed tools are most likely to develop this disorder. Any strenuous use of the hands—ustained grasping, twisting, or flexing—aggravates this condition.

Causes
The carpal tunnel is formed by the carpal bones and the transverse carpal ligament. Inflammation or fibrosis of the tendon sheaths that pass through the carpal tunnel can cause edema and compression of the median nerve.
Many conditions can cause the contents or structure of the carpal tunnel to swell and press the median nerve against the transverse carpal ligament. Such conditions include rheumatoid arthritis, flexor tenosynovitis (commonly associated with rheumatic disease), nerve compression, pregnancy, renal failure, menopause, diabetes mellitus, acromegaly, edema following Colles’ fracture, hypothyroidism, amyloidosis, myxedema, benign tumors, tuberculosis, and other granulomatous diseases. Another source of damage to the median nerve is dislocation or acute sprain of the wrist.

Signs and symptoms
The patient with carpal tunnel syndrome usually complains of weakness, pain, burning, numbness, or tingling in the involved hands. This paresthesia affects the thumb, forefinger, middle finger, and half of the fourth finger. The patient is unable to clench his hand into a fist. The nails may be atrophic; the skin, dry and shiny.
Because of vasodilation and venous stasis, symptoms are usually worse at night and in the morning. The pain may spread to the forearm and, in severe cases, as far as the shoulder. The patient can usually relieve such pain by shaking his hands vigorously or dangling his arms at his side.

Diagnosis
Physical examination reveals decreased sensation to light touch or pinpricks in the affected fingers. Thenar muscle atrophy occurs in about half of all cases of carpal tunnel syndrome.
The patient exhibits a positive Tinel’s sign (tingling over the median nerve on light percussion). He also responds positively to Phalen’s wrist-flexion test (holding the forearms vertically and allowing both hands to drop into complete flexion at the wrists for 1 minute reproduces symptoms of carpal tunnel syndrome).
A compression test supports this diagnosis: A blood pressure cuff inflated above systolic pressure on the forearm for 1 to 2 minutes provokes pain and paresthesia along the distribution of the median nerve.
Electromyography detects a median nerve motor conduction delay of more than 5 msec. Other laboratory tests may identify underlying disease.

Treatment
Treatment should be conservative at first, including resting the hands by splinting the wrist in neutral extension for 1 to 2 weeks. If a definite link has been established between the patient’s occupation and the development of carpal tunnel syndrome, he may need to seek other work. Effective treatment may also require correction of an underlying disorder.
When conservative treatment fails, the only alternative is surgical decompression of the nerve by resecting the entire transverse carpal tunnel ligament or by using endoscopic surgical techniques. Neurolysis (freeing of the nerve fibers) may also be necessary.

Special considerations

• Administer an analgesic if needed.
• Encourage the patient to use his hands as much as possible. If his dominant hand has been impaired, you may need to help with eating and bathing.
• Teach the patient how to apply a splint. Tell him not to make it too tight. Show him how to remove the splint to perform gentle range-of-motion exercises, which should be done daily. Make sure the patient knows how to do these exercises before he’s discharged.
• After surgery, monitor vital signs, and regularly check the color, sensation, and motion of the affected hand.
• Advise the patient who is about to be discharged to occasionally exercise his hands. If the arm is in a sling, tell him to remove the sling several times a day to do exercises for his elbow and shoulder.
• Suggest occupational counseling for the patient who has to change jobs because of carpal tunnel syndrome.