Carpal Tunnel Syndrome

What is the carpal tunnel?

The carpal tunnel is an anatomic passageway formed by the arched carpal bones of the wrist and a strong ligament called the transverse carpal ligament, which spans these bones. The ligament is located on the palmar (hand up) side of the hand and is attached to the scaphoid and trapezium bones of the wrist on the radial side (thumb side) and to the pisiform and hamate bones on the ulnar side (little finger side) of the wrist.

The carpal tunnel contains the tendons that flex (bend down) the fingers and the median nerve, which supplies sensation (feeling) to the thumb, index, middle fingers, and one half of the ring finger. The median nerve lies directly beneath the transverse carpal ligament and is the softest structure of the carpal tunnel. It is brought against the ligament when bending or straightening the wrist or fingers.

What are the causes?

Carpal tunnel syndrome involves the compression of the median nerve at the wrist, and can be caused by a variety of problems. An increase in the volume of the contents of the carpal tunnel or a decrease in the tunnel space can lead to a situation in which the median nerve is compressed against the transverse carpal ligament. Some common problems that can cause compression of the median nerve in the tunnel include:

• Inflammation or swelling about the tendons within the carpal tunnel
• Fluid retention
• Wrist fractures and dislocations
• Crushing injuries
• Conditions causing hand and forearm swelling
• Rheumatoid arthritis
• Enlargement of the median nerve
• Tumors and tumor like conditions
• Generalized conditions such as pregnancy, hypothyroidism
• Birth control medication
• Repetitive motion

Who gets it?

Carpal tunnel syndrome may be related to sex, age, occupation, hereditary factors and certain medical conditions. It is seen in women more frequently than in men and often occurs after menopause. Statistically the right hand is more frequently involved than the left, however, both hands are often affected. Jobs requiring tools to be used in the palm of the hand with constant gripping and pressure to the hand and wrist area can increase the possibility of developing carpal tunnel syndrome. For example, truck drivers who constantly grip the wheel of their trucks may experience symptoms of this condition. Certain occupations have a higher risk of developing carpel tunnel syndrome. 

What are the signs and symptoms?

Numbness, burning, or tingling of one or all of the thumb, index, middle, and half of the ring fingers are very common manifestations of carpal tunnel syndrome. These symptoms usually occur at night or in the early hours of the morning and may awaken the patient. Partial relief may be obtained by shaking and elevating the hands. At times the aching pain will extend up the arm and may also be present in the elbow and as far up as the shoulder and neck.

A decrease in the sensation or feeling of the hand may occur, causing clumsiness and weakness. Patients often find themselves dropping objects, and may be unable to tell the precise hotness or coldness of an object. The sensation of light touch may be decreased, and "coldness and dryness of the hand may occur.

Water retention (swelling) plays a significant role in the production of the symptoms of carpal tunnel syndrome. The consequent expansion of the contents of the carpal tunnel is especially common at night due to the pooling and accumulation of fluid with lack of exercise and motion. Relief is often obtained after the hands have been in use or have been exercised for a period of time.

On the palm, just below the thumb, a fat bulging pad of muscle called the thenar muscle group is noticeable. With carpal tunnel syndrome this muscle group may begin to waste away and give a flattened appearance to the palm when compared to the other hand.

How is it diagnosed?

When a patient is examined, the physician may choose to perform several tests that help to diagnose carpal tunnel syndrome. A test known as "Tinel's sign" may be performed by lightly tapping the wrist area over the median nerve. A patient with carpal tunnel syndrome may have a tingling sensation going into the areas to which sensation is supplied by the median nerve. In "Phalen's test", the elbows are rested on a flat surface, and the arms are held up with the wrists fully bent down for about one minute. This may cause pain and tingling in the same areas as the Tinel's test. A "2 point test" may be done to determine the sensory ability or the amount of feeling supplied by the median nerve in the fingers. This is performed by using a small instrument and touching the finger with either one or two points while the patient is not looking. In some patients with a compressed median nerve, the ability to feel 2 points together is diminished.

Nerve conduction studies may be performed at a special lab when the patient's visible symptoms of carpal tunnel syndrome are not clear or require further documentation. The median nerve is stimulated with an electrode at the wrist, and the time needed to conduct the impulse to the muscles of the thumb and to an electrode placed on the end of the index finger is recorded. Nerve conduction time may slow if the median nerve is compressed.

X-rays will seldom reveal carpal tunnel abnormalities, but can reveal fractures, arthritis and injuries of the wrist that may be responsible for carpal tunnel symptoms.

Can it be treated without surgery?

Many patients with carpal tunnel syndrome can be treated without surgical procedures. Patients treated successfully using conservative treatment usually have mild symptoms without showing any loss of sensation in their fingers and no thenar muscle wasting. Conservative treatment of this problem includes immobilization of the wrist in neutral position. This is usually accomplished by a prefabricated or custom splint. Depending on the severity of the symptoms and the physician's preferences, patients may be asked to wear their splint during the day and/or night. Splinting is dependent on each patient's condition, and the length of time the splint is needed varies. Usually, a splint is worn until the symptoms quiet down, which may be approximately three weeks to a month.

Patients with certain medical conditions (rheumatoid/inflammatory arthritis, hypothyroidism, diabetes, and fluid retention) may experience reduction of their carpal tunnel symptoms by medications to treat their underlying medical disorder.

Physicians may also choose to inject a steroid preparation into the carpal tunnel, which may decrease inflammation and swelling and relieve the symptom producing pressure on the median nerve. The injection may also help establish the diagnosis and indicate how much of one's total discomfort is actually due to compression of the median nerve.

How is it treated surgically?  

In some patients with carpal tunnel syndrome, symptoms are not relieved with conservative treatment, or are of such severity that surgery is advised. Examples are patients initially seen who have thenar muscle wasting, weakness, and numbness demonstrated by their two point test.

The surgical procedure usually is performed on an outpatient basis. An incision is made on the palm of the hand, and the surgeon will divide the transverse carpal ligament. This releases the compression of the tunnel contents. If needed, the median nerve at this time is separated from surrounding adhesions, a procedure called neurolysis. Additional procedures, such as stripping a thickened outer covering (epineurium) from the nerve, may also be carried out depending on the preoperative findings and the appearance of the nerve at surgery.

What can I expect after surgery?

It is important to elevate the hand postoperatively for at least 2-3 days to prevent swelling of the wrist and hand.

Post-operative care of the wrist and hand is of great importance. A compressive dressing is usually applied along with a plaster splint to hold the wrist in an extended position. The surgical dressing is removed after 1-2 weeks, depending on your physician's preference, and active wrist motion is started. Patients can anticipate soreness from their incision for approximately 4-6 weeks and some discomfort from deep pressure for as long as several additional months. However, their symptoms of tingling and night paresthesias are usually relieved immediately following surgery. Improvements in strength and numbness depend on the extent of nerve damage prior to treatment.

Stitches used to close the skin are removed approximately 9-10 days following surgery. The hand should be kept clean and dry until the stitches are removed. Care should be taken while bathing to keep the hand and dressing from becoming wet. Only the nurse or physician should remove the dressing.

How long will I be disabled?

Surgical treatment of carpal tunnel syndrome usually involves a temporary partial disability of the involved hand for approximately one month (longer in patients who work hard with their hands). Recovery of normal grip strength may be delayed for a few additional weeks to months, and the physician may recommend hand therapy to regain strength and range of motion to the fingers and hand. Activities requiring direct impact on the palm of the operated hand may not be comfortably resumed for as long as 8-12 weeks following surgery.