Carpal tunnel syndrome is a condition that causes pain and tingling in the forearm, hand and fingers. The condition is caused by compression of the median nerve which passes through the carpal tunnel. The median nerve controls movement and sensation in the hand and in the case of carpal tunnel syndrome, this nerve is basically pinched at the wrist.
What happens in carpal tunnel syndrome
The carpal tunnel is a channel through which the median nerve and nine tendons pass from the forearm into the hand. Swelling within the tunnel causes pressure to build up and compress the median nerve which eventually causes numbness, tingling, and pain in the arm, fingers and hand.
Causes of carpal tunnel syndrome
The exact cause of this condition is unclear. However, it is known that the pressure on the nerve may have several causes and these include:
- Swelling in the lining of the flexor tendons, known of as tenosynovitis
- Fracture, joint dislocation or arthritis that narrows the tunnel
- Bending the wrist for long periods
- Fluid retention during pregnancy can cause swelling and symptoms of the condition. This usually goes away after delivery.
- Thyroid disease or disorder, diabetes and rheumatoid arthritis are all conditions that are associated with carpal tunnel syndrome.
Symptoms of carpal tunnel syndrome
Typical symptoms affecting the hand and fingers in carpal tunnel syndrome include:
- A combination of the above three
- Weakness of grip and tendency to drop things held in the hand
In long term sufferers, the muscles at the thumb base may shrink causing difficulty with the pinch mechanism. The numbness or tingling is most commonly felt in the thumb, index, middle and ring fingers. The symptoms are usually felt at night but may also persist throughout the day when performing daily activities such as driving or reading.
Diagnosis is made using a details of any medical conditions, how a person uses their hands, and history of any earlier injuries. Other diagnostic tests include:
X-ray of the joint to check for fractures, dislocations and arthritis.
A nerve conduction study (NCV) and an electromyogram (EMG) may be performed to confirm the diagnosis and also check for any other nerve dysfunction.
Often, surgery is not required to relieve symptoms. Some examples of approaches to treating carpal tunnel syndrome include:
- Identification and treatment of the underlying medical conditions.
- Changing patterns of hand use.
- Keeping the wrist straight with the use of a splint, particularly at night when symptoms may be more severe and interfering with sleep.
- Some patients may benefit from a steroid injection into the carpal tunnel which can reduce the swelling around the nerve.
Surgery is considered when symptoms fail to improve. The pressure over the nerve is decreased by cutting the ligament that forms the top of the tunnel on the palm side of the hand. The overall effect of the surgery is enlargement of the tunnel and therefore a decrease in the pressure exerted on the nerve.
Reviewed by Sally Robertson, BSc