Carpal tunnel syndrome is one of the most common forms of entrapment neuropathies. These conditions as a group affect an estimated 4 to 10 million people in the US.1 Carpal tunnel syndrome is characterized by pain, numbness, and weakness in the wrist and hand, radiating up the arm and into the fingers.
The symptoms result from narrowing or swelling in the area of the wrist exerting pressure on the median nerve that extends from the forearm through the wrist to the palm of the hand. At the wrist, the median nerve passes through the carpal tunnel, a rigid structure made of ligaments and bone located near the base of the hand. The carpal tunnel serves as a housing to protect the median nerve and tendons. The function of the median nerve includes control of sensation to the palm side of the thumb and fingers (excluding the little finger) and impulses to selected muscles in the hand responsible for the movement of the thumb and fingers.
Carpal tunnel syndrome is a common complication of RA, due to the increased risk for swelling of joints and tendons. Damage that results from RA can cause compression of the median nerve. In population-based studies, RA has been shown to be one of the most frequent conditions linked to carpal tunnel syndrome.2,3
What are symptoms of carpal tunnel syndrome?
The symptoms of carpal tunnel syndrome may start gradually in the palm of the hand and fingers (usually affecting the middle fingers and thumb) as a burning, tingling, or itching sensation. Even though there may be little or no swelling involved, a person may feel like their fingers are swollen and lack normal strength.
The initial onset of the symptoms may be during the night, but as the condition worsens, symptoms may become apparent during the day, resulting in reduced grip strength, the inability to grasp small objects, and decreased nerve sensation (for example, an inability to distinguish between hot and cold). Carpal tunnel syndrome tends to affect the dominant hand first and cause the most severe symptoms in this hand. The pain and dysfunction caused by carpal tunnel syndrome can become quite severe and debilitating over time.
At-risk groups for carpal tunnel syndrome
Carpal tunnel syndrome can occur when the tendons passing through the carpal tunnel become irritated and thicken or when other swelling occurs within the carpal tunnel structure causing compression of the median nerve. The condition typically only affects adults, and women are 3 times more likely to develop carpal tunnel syndrome, perhaps because the carpal tunnel tends to be smaller in women than in men.
The syndrome is more common (almost 3 times as common) among people who do assembly-line work (sewing, manufacturing, cleaning, finishing, and packing of meat, poultry, or fish) compared with other types of occupations. Poor ergonomics can lead to carpal tunnel syndrome in musicians, typists, or data entry specialists.
Risk factors for carpal tunnel syndrome
Several factors may contribute to compression of the median nerve resulting in carpal tunnel syndrome. It is thought that some people are predisposed to the disorder because their carpal tunnel may be smaller than in others. Injury or trauma (a fracture or sprain) to the wrist, use of vibrating hand tools, retention of fluid during menopause or pregnancy, work stress, or the development of a cyst or tumor in or near the tunnel may contribute to the development of carpal tunnel syndrome. Additionally, a number of medical conditions, including an overactive pituitary gland, RA, hypothyroidism, or diabetes may increase the risk for carpal tunnel syndrome.
What are available treatment options for carpal tunnel syndrome?
In patients with RA who develop carpal tunnel syndrome, the condition is commonly treated with anti-inflammatory drugs or cortisone injections to reduce inflammation. Splinting is also used to immobilize the wrist, typically during the nighttime to prevent the patient from flexing the wrist (many people tend to sleep with flexed wrists).
In some cases where the condition is severe and not responsive to other treatments, surgery may be used for decompression of the tunnel to reduce pressure on and release the nerve.