Carpal tunnel syndrome is compression of the median nerve at the wrist, which may result in numbness, tingling, weakness, or muscle damage in the hand and fingers.

Carpal tunnel syndrome is caused by pressure on the median nerve at the point where it passes through the wrist. The median nerve supplies sensation to the thumb-side of the palm, and to the thumb, index finger, middle finger, and the thumb-side of the ring finger. It also helps with movement to part of the hand.

The area where the nerve enters the hand is called the carpal tunnel. Since the passageway is stiff, any swelling in this area can put pressure on the nerve. This may also be called entrapment of the nerve.

Injury to the wrist area can cause swelling of the tissues and carpal tunnel syndrome. This type of injury may be caused by sports such as racquetball and handball, or occur during sewing, typing, driving, assembly-line work, painting, writing, use of tools (especially hand tools or tools that vibrate), or similar activities.

Carpal tunnel syndrome is common in people who perform repetitive motions of the hand and wrist, such as typing. The condition occurs most often in people 30 to 60 years old, and is more common in women than men.

Some of the conditions associated with carpal tunnel syndrome include:

• Pregnancy
• Premenstrual syndrome (PMS)
• Menopause
• Rheumatoid arthritis
• Renal failure
• Diabetes
• Acromegaly
• Hypothyroidism
• Multiple myeloma
• Obesity
• Recent tuberculosis
• Recent fungal infection
• High blood pressure

• Weakness in one or both hands
• Numbness or tingling in the thumb and next two or three fingers of one or both hands
• Numbness or tingling of the palm of the hand
• Pain in wrist or hand in one or both hands
• Pain extending to the elbow
• Problems with fine finger movements (coordination) in one or both hands
• Weak grip or difficulty carrying bags (a common complaint)
• Wasting away of the muscle under the thumb (in advanced or long-term cases)

During a physical examination, the doctor may identify numbness in the palm, thumb, index finger, middle finger, and thumb-side of the ring finger. Hand grip may be weak.

Tapping over the median nerve at the wrist may cause pain to shoot from the wrist to the hand (Tinel's sign). Bending the wrist forward all the way (Phalen's test) for 60 seconds will usually result in numbness, tingling, or weakness.

Electromyography and nerve conduction velocity may be performed, showing decreased conduction across the wrist. Wrist x-rays should be obtained to ensure that other problems (such as wrist arthritis) are not the cause of the patient's pain.