Carpal tunnel syndrome is a type of ‘compression neuropathy’, whereby a nerve (called the median nerve) becomes abnormally compressed (squashed) within the carpal tunnel of your wrist. The median nerve supplies sensation to the thumb, index, middle and ring fingers (and also power to the muscles at the base of your thumb). Carpal tunnel syndrome typically causes numbness and pins and needles (tingling) of the fingers, and sometimes clumsiness, weakness and pain.

The carpal tunnel is a short tunnel on the palm side of your wrist that contains the median nerve and the tendons that bend your fingers and thumb. Carpus is the Greek word for wrist and the word carpal therefore relates to the wrist. A thick ligament covers the nerve and tendons to form the ‘roof’ of the carpal tunnel. Wrist position (especially bending of the wrist at night or with certain activities) can increase the pressure within the carpal tunnel. Abnormally increased pressure will squash (compress) the median nerve and reduce the nerve’s blood supply and cause symptoms in the fingers and hand.

Although the little finger is not typically affected in carpal tunnel syndrome, it is not uncommon for some to feel numbness in all fingers. Numbness in the little finger may represent a different condition such as cubital tunnel syndrome.

Carpal tunnel syndrome is common and the cause remains unknown for most people. Any condition that increases the pressure within the carpal tunnel will squash (compress) the median nerve and potentially cause symptoms in the fingers and hand.

Sometimes carpal tunnel syndrome develops in those with inflammatory conditions like rheumatoid arthritis, or in those with diabetes, thyroid problems, obesity, the menopause or with other less common health conditions. Carpal tunnel syndrome can also occur following a broken wrist (distal radius fracture). Pregnancy can cause carpal tunnel syndrome; however, the symptoms will usually settle after delivery. For most, the cause is not identifiable.

Some of the potential symptoms of carpal tunnel syndrome are listed below.

Typically present:

• Numbness and pins and needles (tingling) in the thumb, index, middle and ring fingers.

• Finger tingling that is worse at night or first thing in the morning (or when holding your phone to your ear or driving your car).

Sometimes present:

• Constant numbness and pins and needles (that can be unrelated to activity or time of day).

• Weakness of grip and/or clumsiness (including dropping of objects).

• Pain in the wrist or forearm (especially at night).

• Muscle wasting at the thumb base (muscles appear smaller).

It is important to correctly diagnose carpal tunnel syndrome and exclude other causes of hand numbness, pins and needles or pain; such as cubital tunnel syndrome, nerve entrapment in the neck or arthritis. The diagnosis is usually made on the history (your symptoms), clinical examination and, commonly, nerve conduction studies (also called neurophysiology testing) are used. Nerve conduction studies assess the speed of nerve signal transmission (termed conduction) - such as across your wrist - to help confirm the diagnosis and the severity of nerve dysfunction. Nerve conduction studies can be uncomfortable but are usually well tolerated. 

On occasions, very mild carpal tunnel syndrome that is sensitive to certain wrist positions will not be identified on nerve conduction studies (i.e. the test can be normal). Although a normal result provides some reassurance regarding nerve function, the cause of your symptoms can remain unclear. A trial injection of steroid (e.g. cortisone) into the carpal tunnel can sometimes be considered to help prove or disprove the diagnosis of carpal tunnel syndrome.

For most, the cause of carpal tunnel syndrome is not identifiable, and the treatment options below can be considered. When carpal tunnel syndrome is thought to be linked to an identifiable cause or condition (e.g. rheumatoid arthritis, thyroid problems, menopause), symptoms may improve when treating the underlying cause.

Non-surgical treatment options include wrist splintage (often worn at night), simple pain killers (if pain is a feature) and, sometimes, physiotherapy (for nerve gliding exercises) or steroid injection (e.g. cortisone). A steroid injection can be a useful treatment in selected patients, especially if the nerve conduction study demonstrates only very mild carpal tunnel syndrome. However, often only a minority who receive a steroid injection for carpal tunnel syndrome will gain long-term relief or benefit.

Surgical treatment is carpal tunnel decompression (also termed release), whereby the ligament overlying the median nerve is released through a short incision on the palm side of your wrist. This surgery opens up the carpal tunnel to provide more space for the nerve to function and recover. Following surgery, nerve recovery and symptom improvement can be incomplete (especially for more severe forms of carpal tunnel syndrome).

Carpal tunnel surgery is usually performed under local anaesthesia.

The potential risks of surgery (general and specific) will be discussed if surgery is an option.

Matthew offers all of the above treatments. He can refer you for physiotherapy if required.

You can read more detailed information regarding carpal tunnel syndrome on the Lothian Hand Unit website here.

The British Society for Surgery of the Hand (BSSH) has an informative webpage on carpal tunnel syndrome here which can be downloaded as a patient information leaflet PDF here.