Carpal tunnel syndrome (CTS) is the collection of symptoms and signs associated with median neuropathy at the carpal tunnel. Most CTS is related to idiopathic compression of the median nerve as it travels through the wrist at the carpal tunnel (IMNCT). Idiopathic means that there is no other disease process contributing to pressure on the nerve. As with most structural issues, it occurs in both hands, and the strongest risk factor is genetics.

Other conditions can cause CTS such as wrist fracture or rheumatoid arthritis. When CTS are diagnosed, they also may check for transthyretin amyloidosis. Transthyretin amyloidosis are often seen in conjunction with CTS. After fracture, swelling, bleeding, and deformity compress the median nerve. With rheumatoid arthritis, the enlarged synovial lining of the tendons causes compression.

The main symptoms are numbness and tingling in the thumb, index finger, middle finger and the thumb side of the ring finger. People often report pain, but pain without tingling is not characteristic of IMNCT. Rather, the numbness can be so intense that it is described as painful.

Symptoms are typically most troublesome at night. Untreated, and over years to decades, IMNCT causes loss of sensibility and weakness and shrinkage (atrophy) of the muscles at the base of the thumb.

Work-related factors such as vibration, wrist extension or flexion, hand force, and repetition increase the risk of developing CTS. The only certain risk factor for IMNCT is genetics. All other risk factors are open to debate. It is important to consider IMNCT separately from CTS in diseases such as rheumatoid arthritis.

Diagnosis of IMNCT can be made with a high probability based on characteristic symptoms and signs. IMNCT can be measured with electrodiagnostic tests.

People wake less often at night if they wear a wrist splint. Injection of corticosteroids may or may not alleviate better than simulated (placebo) injections. There is no evidence that corticosteroid injection alters the natural history of the disease, which seems to be a gradual progression of neuropathy.

Surgery to cut the transverse carpal ligament is the only known disease modifying treatment.