Carpal Tunnel Syndrome

Overview

Loss of sensory function can occur in a number of ways but the direct cause is usually damage or disturbance to the nerves responsible for sensation in a particular area. This normally occurs as a result of degenerative diseases, injury, infections or nutritional deficiencies. In the case of the median nerve, which is one of the main nerves responsible for sensation in the forearm and hand, one of the most common disturbances occurs in the form of carpal tunnel syndrome (CTS). As it traverses the length of the arm and passes into the hand, the median nerve must travel through a passage in the wrist known as the carpal tunnel.

When, for a variety of possible reasons, space within the carpal tunnel becomes restricted, a pressure is exerted on this crucial nerve and the patient experiences numbness, pain or loss of motor function in the hand. In severe cases, there can be permanent nerve and muscle damage. Surgical treatment, known as ‘carpal tunnel release’ may be recommended in order to remove the obstruction that is responsible for compression of the median nerve.

What is carpal tunnel syndrome?

Carpal tunnel syndrome (CTS) is a kind of peripheral neuropathy or a condition involving impairment in the functioning of a nerve of the peripheral nervous system. CTS affects the median nerve which is one of the major nerves responsible for sensation and motor function in the hand. ‘Carpal tunnel’ is the name given to the narrow passageway in the wrist through which the median nerve and nine flexor tendons must pass. This space is bounded by the carpal bones of the wrist, with a tough band of connective tissue (transverse carpal ligament) forming the roof of the ‘tunnel’.

Sometimes, the transverse ligament or the lining of the tendons swell within this constricted space, pinching or compressing the median nerve. This interrupts the flow of blood supply to the nerve and affects its normal functioning which results in loss of sensory and motor function in the hand.

Causes of carpal tunnel syndrome

The median nerve may become trapped or compressed in a number of ways. The biological causes for this are not well understood although it is acknowledged that genetic predisposition is likely to play a role. Other underlying disorders can also be responsible.

• Injury, such as fracture of the wrist bones or a sprain.
• Hypertension.
• Hormonal changes associated with pregnancy or menopause.
• Having a family history of CTS raises the likelihood of developing this condition. For instance, some families may display a hereditary trait of having narrow wrists.
• Performing repetitive tasks involving the use of violently vibrating tools such as jackhammers or chainsaws. Any activity that exerts repeated pressures and excessive force on the hands and wrist can lead to CTS over the long term.
• Maintaining poor wrist posture over extended periods of time.
• Medical disorders such as rheumatoid arthritis, thyroid dysfunction, and diabetes can also be responsible.
• An abnormal growth in the carpal tunnel, such as a calcium deposit, cyst or tumor.
• The risk of developing CTS increases with age.
• Being overweight or obese can also lead to CTS.
• Smoking is another risk factor.

Symptoms and signs

The signs of CTS develop slowly and eventually grow in intensity as the condition worsens. Those who suffer from CTS commonly experience the following symptoms which are typical of disturbance to the motor and sensory function:

• Pain, ranging from mild to severe. It usually occurs in the fingers but may also radiate up into the arm.
• A burning or itching sensation in the fingers other than the little finger.
• Numbness or intermittent loss of feeling in the hand.
• Sharp shockwave like sensations, particularly in the fingers other than the little finger.
• Inability to maintain firm or precise grip.
• Weakness in the hand.
• Inability to detect the difference between hot or cold objects by touch.

The two types of carpal tunnel syndrome

There are two main types of carpal tunnel syndrome:

• Acute CTS: This form is relatively less common. It is generally associated with trauma such as fracture of the distal radius.
• Chronic CTS: This is encountered more frequently and is generally characterized by a slower onset of symptoms.

Possible complications

Initially, the symptoms are intermittent. However, if the pressure constricting the median nerve remains unrelieved, its protective sheath can wear away. This can cause permanent nerve damage. Muscles in the hand, particularly the muscle located at the base of the thumb, can atrophy and shrink noticeably. Thus, permanent loss of muscular and nerve function in the hand is possible in severe cases of CTS.

Diagnosing carpal tunnel syndrome

Physical examination is the necessary first step in detecting carpal tunnel syndrome. The physician will generally perform what is known as the Tinel test by lightly tapping on the area above the nerve to check for signs of tingling. The patient may also be asked to keep the wrists flexed or bent for some time to check whether this results in numbness or tingling. Thumb grip is also assessed to look for signs of weakness in the muscles at its base.

The median nerve does not service the little finger. Hence, any such symptoms also appearing in that finger would most likely rule out CTS. X-rays help to detect any fractures or ligament injuries that may be responsible. An ultrasound or magnetic resonance imaging (MRI) may also be recommended. Electromyography tests are helpful in assessing muscular responses. Assessing nerve conductivity may also require further test procedures. Compromised nerve or muscle function, combined with other symptoms and a relevant medical history must all be considered in order to make a definite diagnosis.

Treatment and prevention

Treatment 

Medication 

• Splints – Wearing a splint at night is the best way to avoid pain related to carpal tunnel syndrome. These splints hold the patient’s wrist in place and make sure that there is no additional or excessive strain on the median nerve.
• Nonsteroidal anti-inflammatory drugs – These medications are prescribed to reduce inflammation and pain in the wrist.
• Corticosteroids – These are injected and not given orally to the patent. These medications help in reducing pain and inflammation.

Surgery 

• Endoscopy – Here the surgeon uses an endoscope (a tube with a camera in the front) to see the condition of the median nerve.
• Open surgery – Here, the surgeon will make an incision in the patient’s palm and cut through the ligament, reaching the median nerve and relieving the compression on the nerve.

Prevention 

• Avoid putting a strain on your wrists.
• Take breaks, this helps in giving your wrists some rest.
• Do mild exercises, to help relieve the soreness in your wrists.
• Do not expose your hands to extreme temperature; make sure to keep them warm.

References