Carpal tunnel syndrome

What it is

Carpal tunnel syndrome is the most common entrapment neuropathy of the upper extremity. It is caused by compression of the median nerve as it travels through the carpal tunnel.

Causes and risk

The causes listed are:

• Idiopathic
• Pregnancy
• Oedema, for example heart failure
• Lunate fracture
• Rheumatoid arthritis

Carpal tunnel syndrome is also one of the extra-articular manifestations of rheumatoid arthritis, listed there with pulmonary nodules in Caplan's syndrome, Felty's syndrome, secondary Sjogren's syndrome, anaemia of chronic disease and amyloidosis. So a patient with rheumatoid hands who reports night tingling has two causes on the same page for it.

The typical history

Pain, pins and needles in the thumb, index and middle finger. Unusually the symptoms may ascend proximally. The patient shakes his hand to obtain relief, classically at night.

The night is the whole of the history question. In the worked case it is a female teacher with pain and tingling in the index and middle finger worse at night, and that alone is enough to name the diagnosis. The hand shakes for relief, and that is the second half of the same history.

In more severe cases motor fibers are affected, leading to weakness of thumb abduction and opposition.