(See also Overview and Evaluation of Hand Disorders.)
Carpal tunnel syndrome is very common and most often occurs in women aged 30 to 50. Risk factors include rheumatoid arthritis or other wrist arthritis (sometimes the presenting manifestation), diabetes mellitus, hypothyroidism, acromegaly, primary, cardiac or dialysis-associated amyloidosis, and pregnancy-induced edema in the carpal tunnel. Activities or jobs that require repetitive flexion and extension of the wrist may contribute, but rarely. Most cases are idiopathic.
Symptoms of carpal tunnel syndrome include pain of the hand and wrist associated with tingling and numbness, classically distributed along the median nerve (the palmar side of the thumb, the index and middle fingers, and the radial half of the ring finger) but possibly involving the entire hand. Typically, the patient wakes at night with burning or aching pain and with numbness and tingling and shakes the hand to obtain relief and restore sensation. Thenar atrophy and weakness of thumb opposition and abduction may develop late.
The diagnosis of carpal tunnel syndrome is strongly suggested by the Tinel sign, in which median nerve paresthesias are reproduced by tapping at the volar surface of the wrist over the site of the median nerve in the carpal tunnel. Reproduction of tingling with wrist flexion (Phalen sign) or with direct pressure on the nerve at the wrist in a neutral position (median nerve compression test) is also suggestive. The median nerve compression test is positive if symptoms develop within 30 seconds. However, clinical differentiation from other types of peripheral neuropathy may sometimes be difficult.
If symptoms are severe or the diagnosis is uncertain, nerve conduction testing should be done on the affected arm for diagnosis and to exclude a more proximal neuropathy.
Changing the position of computer keyboards and making other ergonomic corrections may occasionally provide relief. Otherwise, treatment of carpal tunnel syndrome includes wearing a lightweight neutral wrist splint (see Figure: Neutral wrist splint), especially at night, and taking mild analgesics (eg, acetaminophen, nonsteroidal anti-inflammatory drugs).
If these measures do not control symptoms, a mixture of an anesthetic and a corticosteroid (eg, 1.5 mL of a 4-mg/mL dexamethasone solution mixed with 1.5 mL of 1% lidocaine) may be injected into the carpal tunnel at a site just ulnar to the palmaris longus tendon and proximal to the distal crease at the wrist. This is more often effective for milder or pregnancy-related carpal tunnel syndrome.
If bothersome symptoms persist or recur or if hand weakness and thenar wasting develop, the carpal tunnel can be surgically decompressed by using an open or endoscopic technique.
Although carpal tunnel syndrome has many risk factors, most cases are idiopathic.
Typical symptoms include wrist and hand pain with tingling and numbness along the palmar side of the thumb, the index and middle fingers, and the radial half of the ring finger.
Reproducing symptoms with wrist flexion or pressure over the median nerve can provide helpful diagnostic clues.
Treat first with ergonomic corrections, then try splinting and analgesics, corticosteroid injection, and, for weakness, muscle wasting, and/or severe unresponsive symptoms, surgical decompression.