The sensibility of the hand, except the little finger, is based on the major sensory nerve of the hand – the median nerve. At wrist level, the median nerve passes through a  narrow canal – the carpal tunnel – together with several flexor tendons of the hand.

A carpal tunnel syndrome (CTS) means an entrapment of the  median nerve in the carpal tunnel. The median nerve is subjected to an external pressure. The reason can be swelling in the surrounding flexor tendons sheaths, but most often no special reason can be identified. The increased pressure in the carpal tunnel results in impaired microcirculation in the median nerve and damage to the myelin sheaths, surrounding nerve fibres.

Clinically an early carpal tunnel syndrome is characterized by nocturnal numbness and parasthesiae  – ” pins and needles” -  in the fingers except the little fingers. The patient may ” wake up because the hand falls asleep”. During daytime, the hand may be symptom free. With time, the problems may however become chronic and troubling also during the day. At an even more advanced stage, there may be pain and atrophy of the thenar muscles of the thumb.

Carpal tunnel syndrome can be cured by a surgical procedure where the nerve is decompressed by a volar incision dividing the carpal ligament.

About 3 % of the population suffer from CTS,  usually middle-aged women. The problem is common in younger women at a late stage of pregnancy. Many factors can contribute and increase the risk to develop CTS. One important such factor is repeated, monotonous flexion movements of the wrist.

CTS can be seen as a complication to hard manual work and the use of handhold vibrating tools. Use of  heavy tools combined with monotonous wrist movements can be one reason, but the use of handhold vibrating tools is probably an important factor in itself. Vibrations from the hand can  be transferred to the carpal tunnel and  affect the median  nerve – which may already be stressed as a result of monotonous wrist movements.

It is important to clarify which problems are caused by vibrations and carpal tunnel syndrome respectively. A surgical procedure aiming at decompression of the median nerve in the carpal tunnel may cure problems, which are based on the nerve entrapment, but such a procedure, have  no effects on vibration-induced injuries to nerves in the hand and fingers.