Carpal tunnel syndrome occurs on compression of the median nerve, which that is the nerve connecting the hand with the brain, and, therefore, allowing the movements of the fingers, the perception of pain and temperature, and control of the sweating of the palm. The causes of such compression are generally related to occupational actions (e.g. highly repetitive and prolonged movements, poor posture of the shoulders and arms, excessive use of a computer mouse or keyboard), and traumatic events (e.g. injuries, sprains).

Other causes associated with carpal tunnel syndrome, however, may be chronic and involve certain physiological conditions such as diabetes mellitus, rheumatoid arthritis, amyloidosis, hypothyroidism, acromegaly, high blood pressure, renal failure, fungal infection, pregnancy, use of oral contraceptives, premenstrual syndrome, menopause, deforming arthritis, osteoarthritis, etc. Due to one or more of such causes, there is an increase of pressure inside the carpal tunnel which, combined with the extension of tendons and nerves, leads to the onset of inflammation (or tenosynovitis) of the flexor tendon sheath. The size of the carpal tunnel is thus reduced, compressing the median nerve.

Typical symptoms begin with a burning or tingling of the hand, particularly in the first three fingers. As the syndrome progresses, it may also cause numbness and swelling of the hand and pains that can worsen especially at night and in the morning, and which can extend up to the elbow. If neglected, such chronic inflammation may lead to a loss of sensitivity in the fingers and of strength in the entire hand.