What is Carpal Tunnel Syndrome?
Carpal tunnel syndrome is a condition which is brought on by increased pressure in the wrist causing a nerve to be pinched. The nerve reacts to this pressure by sending signals of numbness, tingling and pain to the hand and occasionally the forearm. In most cases, releasing the pressure will reduce the amount of pinching upon the nerve and alleviate symptoms.
What is the Carpal Tunnel?
The carpal “tunnel” is a channel structure located within the wrist. It is made of a semi-circle of bones, connected at the tips by a tight ligament called the Transverse Carpal Ligament (see photo A).
Within this tunnel there are nine tendons which help control the movement of your fingers and the median nerve. The tendons are lined with tissue called the tenosynovium, which helps the tendons glide. The tendons are sturdy and can withstand a great deal of motion and force. The median nerve develops at the neck from nerves leaving the spinal cord, travels down the arm, through the carpal tunnel and into your hand (see photo B). The median nerve provides sensation or feeling to the thumb, index, middle and half of the ring finger (see photo C). It also provides muscle strength to a small muscle of the thumb (see photo D). Unlike the tendons which are sturdy, the nerve is delicate and vulnerable to changes in pressure.
What Causes Carpal Tunnel Syndrome?
The cause of carpal tunnel syndrome is predominantly due to increased pressure in the wrist, or carpal tunnel, which pinches the median nerve at the wrist. The increased pressure can be caused by many factors:
- Swelling of the tendon lining, or tenosynovitis
- Fractures (breaks in the bone), dislocations or arthritis
- Awkward wrist positions, such as keeping the wrist in a bent position for long periods of time
- Gripping for long periods of time (e.g., driving) bringing small muscles into the carpal tunnel for extended periods of time, therefore pinching the nerve
- Fluid retention (e.g., pregnancy, especially in the third trimester)
- Other conditions causing increased swelling or inflammation in the body, such as diabetes, rheumatoid arthritis and thyroid conditions
- Vibratory tools (e.g., jackhammers)
Unfortunately, in many instances, a cause is not fully identified and at times, is unknown.
Carpal tunnel syndrome affects people primarily between the ages of 30 to 55, and women are affected more often than men, by a ratio of 3 to 1.
What Are the Symptoms of Carpal Tunnel Syndrome?
The symptoms of carpal tunnel syndrome include numbness, tingling and occasionally pain. These symptoms occur mostly in the thumb, index, and middle fingers. These symptoms can worsen at night time due to awkward wrist positions and increased swelling in the hands while sleeping. The symptoms may even wake people from sleep. When the symptoms continue for long periods of time, weakness in gripping may occur in the hand. This is due to the pressure affecting the nerve to the small muscle of the thumb. As the symptoms progress, people may notice dropping objects, frequent clumsiness and an inability to pick up small objects, such as a pin. When the nerve is pinched for a long period of time, permanent damage may occur.
How Do We Diagnose Carpal Tunnel Syndrome?
Your physician will take a detailed history of your symptoms, medical history, activities and injuries, then do a thorough physical examination, checking the neck through the hands to assess the median nerve. They will also check for swelling, color changes, strength, motion, and sensation, and perform multiple physical manipulations of your wrist and hand, intentionally increasing the pressure of your carpal tunnel to see if your symptoms are reproduced. An x-ray may be taken to check for arthritis or other bone conditions in the wrist causing swelling. Laboratory tests may need to be checked to assess any other medical conditions which can affect the carpal tunnel. More specific tests may be ordered, such as a Nerve Conduction Test and EMG to assess for the specific condition of the median nerve and rule out pinching of the nerve at another location in the arm or neck.
How Do We Treat Carpal Tunnel Syndrome?
Carpal tunnel syndrome may be treated in a variety of ways, and is dependent on the stage of the disease. In the early stages of the disease, the symptoms are reversible, and less invasive treatment is highly recommended. In later stages of the disease, the nerve may be damaged, and therefore, surgery may be recommended to protect it from further injury. Surgery may also be recommended in those patients whose initial treatment was successful, but their symptoms return again.
The first level of care is to treat the underlying causes of carpal tunnel syndrome, e.g., positioning during work and rest. If the wrists are kept in awkward positions during the day or night, the doctor may recommend a wrist brace to keep the wrist in a steady, neutral position to keep the pressure off the nerve. If there is arthritis, swelling, or muscle tightness, the doctor may recommend hand therapy and medication such as anti-inflammatories for the hand to reduce the swelling. As symptoms progress, the doctor may recommend a cortisone injection to the carpal tunnel to alleviate the swelling immediately surrounding the nerve.
When the symptoms of carpal tunnel syndrome continue for a significant time, or are severe enough, your doctor may recommend surgery. In surgery, the ligament covering the nerve (the transverse carpal ligament) is cut or “released”, increasing the space around the nerve and giving the nerve more room to “breathe” (see photo E). By increasing the space surrounding the nerve, the pressure on the nerve is diminished. If caught early enough, the carpal tunnel symptoms may be relieved completely. However, if there is any existing damage to the nerve from long term issues, symptoms may not improve. In these cases, the nerve is protected from further injury and worsening of the condition. In the majority of cases, the surgery is done as a “same day” procedure in an outpatient surgery setting. The symptoms usually are alleviated within a few days of surgery; however the symptoms can last up to several months after surgery depending on the condition of the nerve. There are many types of incisions and ways to do this surgery, however, the end result is to alleviate the pressure on the median nerve. The incision and surrounding tissue may be sore for weeks or months after the surgery as the tissue recovers. Ultimately, motion and function return to normal within a couple of months from surgery. Some patients may require hand or occupational therapy to guide and assist their recovery after surgery. For those post-surgical patients with severe carpal tunnel syndrome, they can expect a slow, continued improvement of their symptoms for up to one year after surgery.