The carpal tunnel allows the carpal ligament, the medial nerve and other structures in the wrist to pass from the arm into the hand. Repetitive use, lesions or tissue swelling of pregnancy, diabetes or rheumatoid arthritis inflame the tunnel and compress the medial nerve. This nerve energizes the thumb, the second and third finger and the inner side of the fourth finger. When the nerve becomes entrapped, the characteristic symptoms of carpal tunnel syndrome emerge.
Effects on Fingers
According to Current Medical Diagnosis and Treatment 2010, the fingers of the involved hand burn, become numb or tingle. Episodic pain often traces back to a specific repetitive activity such as digging, weeding, typing and cutting with scissors for lengthy periods. Certain sleeping positions further aggravate the tunnel by causing the wrists to stay flexed for prolonged periods during the night. The hand inadvertently folds under, pinches the medial nerve causing pain that interrupts sleep.
Effects on the Thumb
As a result of impaired circulation at the carpal tunnel the meaty area in the palm at the thumb's base loses its muscle tone and atrophies. To evaluate the strength of this muscle the physician uses a test where he attempts to break the hold of the interlocked "O" formed by the thumb and the second finger.
Diagnosis
Hand pain and numbness present most frequently though some people report arm and shoulder discomfort as well. The pattern of the 3 1/2-finger involvement incriminates the medial nerve as the pain source because compression of the ulna nerve affects the lateral half of the fourth finger as well as the little finger. Mechanical tests that produce the symptoms help in the diagnosis and determine the extent of the impairment.
Electrodiagnosis detects any delay of the sensory-motor conduction across the medial nerve. A compromised rate of conduction indicates transmission interference at the carpal tunnel.
Treatment
For nighttime discomfort, a wrist brace prevents flexing and choking of the nerve. Some find wearing the brace during the day lessens the swelling and prevents overworking of the wrist. Ice packs reduce burning pain. Anti-inflammatory medications such as ibuprofen and naproxen offer periods of relief. The doctor might prescribe a stronger drug if those fail. Cortisone injections at the tunnel help reduce swelling. As noted in Current Medical Diagnosis and Treatment 2010, the two circumstances that warrant surgery stem from an atrophied thenar muscle or suspicion of a lesion at the site. During the operation, the surgeon releases the entrapped nerve and removes any lesions.
Prognosis
After surgery, the wrist requires immobilization. The success of the surgery depends on the amount of time spent healing. Using the hand prematurely causes scarring which in itself may impinge the nerve in the future.
References
- Current Medical Diagnosis and Treatment; Stephen J. McPhee and Maxine A. Papadakis; 2010
- Harrison's Manual of Medicine; Anthony S. Fauci et al; 2009
