The median nerve allows sensation and movement in the index and middle fingers and the thumb side of the ring finger. It also stimulates the muscles at the base of the thumb. Carpal tunnel syndrome manifests when the median nerve becomes pinched in a tunnel that has become too narrow.

What are the most common causes?

Swelling of the flexor tendons in the wrist

Tumors, abnormal muscles, bleeding, osteoarthritis and inflammations (synovitis in the flexors).

Conditions which cause fluid retention

Pregnancy, medications, thyroid disease, diabetes, hypothyroidism and amyloidosis.

Narrowing of the tunnel

Most often caused by bony anomalies

Overuse of the wrist

Repetitive flexion movements (strong gripping motions, for example)

What are the symptoms?

Pain or a burning sensation in the hand, forearm and fingers; numbness or a tingling in the hand (especially in the thumb and index finger); increase in symptoms at night, nighttime wakefulness to shake the hand and attempt to ease the numbness; increase in symptoms with activity; the sensation of swelling in the fingers and hand; weakness and loss of fine coordination; skin atrophy.

How is it diagnosed?

Various clinical tests can be performed to evaluate symptoms and assess the condition, including Tinel’s test (tapping the skin over the nerve), Phalen’s test (holding the wrist in a flexed position); and Durkan’s carpal compression test.

Some additional exams may be useful

A study of nerve conduction and an electromyogram (EMG) are useful.