Carpal Tunnel Syndrome
The Median Nerve
The median nerve runs into the hand to supply sensation to the thumb, index finger, long finger, and half of the ring finger. The nerve also supplies a branch to the muscles of the thumb, the thenar muscles.
One of the first symptoms of Carpal Tunnel Syndrome is numbness in the distribution of the median Nerve. This is quickly followed by pain in the same distribution. The pain may also radiate up the arm to the shoulder, and, sometimes the neck. If the condition is allowed to progress, weakness of the thenar muscles can occur. This results in an inability to bring the thumb into opposition with the other fingers and hinders one’s grasp.
Looking at a cross section of the wrist allows one to visualise the anatomy of the Carpal Tunnel. The Carpal Tunnel is an opening into the hand that is made up of the bones of the wrist on the bottom and the Transverse Carpal Ligament on the top. Through this opening, the Median Nerve and the Flexor Tendons run into the hand. The Median Nerve lies just under the Transverse Carpal Ligament.
The Flexor Tendons allow us to move the hand, such as when we grasp objects. The Tendons are covered by a material called Tenosynovium. The Tenosynovium is very slippery, and allows the tendons to glide against each other as the hand is used to grasp objects. Any condition which causes irritation or inflammation of the tendons can result in swelling and thickening of the Tenosynovium. As all of the tendons begin to swell and thicken, the pressure begins to increase in the Carpal Tunnel because the bones and ligaments that make up the tunnel are not able to stretch in response to the swelling. Increased pressure in the Carpal Tunnel begins to squeeze the Median Nerve against the Transverse Carpal Ligament. Eventually, the pressure reaches a point when the nerve can no longer function normally. Pain and numbness in the hand begins.
There are many conditions which can result in irritation and inflammation of the tenosynovium, and eventually cause Carpal Tunnel Syndrome. Different types of arthritis can cause inflammation of the tenosynovium directly. A fracture of the wrist bones may later cause Carpal Tunnel Syndrome if the healed fragments result in abnormal irritation on the flexor tendons. The Key Concept to remember is that anything which causes abnormal pressure on the Median Nerve will result in the symptoms of pain, numbness and weakness of Carpal Tunnel Syndrome.
Diagnosis of Carpal Tunnel Syndrome
Evaluation begins by obtaining a history of the problem, followed by a thorough physical examination. Description of the symptoms and the physical examination are the most important parts in the diagnosis of carpal tunnel syndrome. Commonly, patients will complain first of waking in the middle of the night with pain and a feeling that the whole hand is asleep. Careful investigation usually shows that the little finger is unaffected. This can be a key piece of information to make the diagnosis. Other complaints include numbness while using the hand for gripping activities, such as sweeping, hammering, or driving. The major physical findings reflect that pressure is increased in the carpal tunnel. If more information is needed to make the diagnosis, electrical studies of the nerves in the wrist may be requested. Several tests are available to see how well the Median Nerve is functioning, including the Nerve Conduction Velocity (NCV). This test measures how fast nerve impulses are conducted through the nerve.
Treatment Options in Carpal Tunnel Syndrome
In the early stages of Carpal Tunnel syndrome, a splint will sometimes decrease the symptoms, especially the numbness and pain occurring at night. It may also help control the swelling of the tenosynovium and reduce the symptoms of Carpal Tunnel Syndrome. If this fails to control your symptoms a cortisone injection into the carpal tunnel may be suggested. This medication will decrease the swelling of the tenosynovium and may give temporary relief of symptoms.
If all of the previous treatments fail to control the symptoms of Carpal Tunnel Syndrome, surgery will be required to reduce the pressure on the Median Nerve.
Basic Steps in Carpal Tunnel Release
A small incision, usually less than 5 cms, is made in the palm of the hand. In some severe cases, the incision needs to be extended into the forearm another 1cm or so. After the incision is made through the skin, a structure called the palmar fascia is visible. An incision is made through this material as well, so that the constricting element, the Transverse Carpal Ligament, can be seen.
Once the Transverse Carpal Ligament is visible, it is cut with either a scalpel or scissors, while making sure that the Median Nerve is out of the way and protected.
Once the Transverse Carpal Ligament is cut, the pressure is relieved on the Median Nerve. Finally, the skin incision is sutured. At the end of the procedure, only the skin incision is repaired. The Transverse Carpal Ligament remains open and the gap is slowly filled by scar tissue. A bandage is applied to the hand following surgery. This should be left in place until the first office visit after the surgery. Sutures will be removed 10 – 14 days after surgery. Avoid any heavy use of the hand for 4 weeks after your surgery. Expect the pain and numbness to begin to improve after surgery, but you may have tenderness in the area of the incision for several months.