Carpal tunnel syndrome (CTS) is the most common nerve entrapment disorder. Nerve entrapment refers to a situation where a nerve is being pinched. The carpal tunnel is located on the palm side of the wrist.
The floor and sides of the carpal tunnel are formed by the eight wrist bones and the roof of the tunnel is a tough piece of fibrous tissue, called the flexor retinaculum.
Through this tunnel pass the flexor tendons to the fingers (these tendons are responsible for helping bend the fingers) as well as the median nerve.
CTS occurs when there is undue pressure on the median nerve. This may occur as a result of many conditions including repetitive stress, trauma (such as fractures), arthritis (rheumatoid arthritis, psoriatic arthritis, gout, and pseudogout are among the more common ones), thyroid disease, growth hormone excess, obesity, diabetes, and pregnancy. Most of these conditions cause the swelling within the carpal tunnel which leads to pressure on the median nerve.
When the median nerve becomes compressed, there is slowing or blocking of nerve impulses traveling down the nerve. This leads to loss of both sensory function (being able to feel things) as well as motor function (weakness in the muscles innervated by the median nerve).
Symptoms include numbness, burning, and tingling in the fingers, with gradual weakness in the hand.
Patients will often try to "shake" the numbness out of their fingers. Since symptoms are present often at night, patients will also say they drape their hands over the side of the bed to get relief. Daily activities may be affected. For example, buttoning can become difficult. Patients may drops things. There may also be a sensation of swelling in the fingers, even though swelling is not present on exam.
Other activities that seem to bring on the symptoms include driving, holding a book, or any other activities requiring prolonged bending of the wrist or prolonged grasping.
Symptoms are pronounced in the fingers innervated by the median nerve. These are the thumb, index, middle, and thumb side of the fourth finger.
Symptoms from CTS can also radiate up the arm as high up as the shoulder. This causes difficulty in establishing the diagnosis.
As the condition progresses, atrophy of muscles innervated by the median nerve occurs. This can lead to permanent nerve and muscle damage.
The diagnosis can be made clinically. However, it should be confirmed using electrical nerve conduction tests. There is a small percentage of people who have CTS but who have normal electrical studies.
Diagnostic ultrasound and magnetic resonance imaging (MRI) can also be used for diagnostic purposes.
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