Many people think nothing of it if their hand occasionally goes numb. But this may be a sign of carpal tunnel syndrome, which can cause permanent nerve and muscle damage if left untreated.
One of the most common nerve disorders, carpal tunnel syndrome is caused by a compressed nerve in the carpal tunnel, a narrow passageway on the palm side of the wrist. It affects about 10 per cent of people.
The symptoms usually begin at night and can include tingling, numbness and dull pain.
“This can wake you up several times,” says Dr Veit Braun, an executive board member of the German Neurosurgical Society. “Later the symptoms occur in the daytime, too, for example when you’re cycling or driving a car.”
The carpal tunnel is bound by the carpal bones that make up the wrist, and covered by a band of fibrous connective tissue. Passing through it are the nine flexor tendons that bend the fingers and thumb, and the median nerve.
“This is one of the main nerves of the hand and serves the thumb, index and middle fingers,” says Dr Oliver Kastrup of the German Neurological Society.
Pressure on the nerve is usually due to swelling of the flexor tendons in the carpal tunnel.
One presumed cause of this is hormonal changes, which would explain why some 70 per cent of patients are women, particularly those over 50 years.
A wrist fracture can also narrow the carpal tunnel.
“In rare cases, carpal tunnel syndrome can be caused by repetitive strain,” said Dr Joerg van Schoonhoven, general secretary of the German Hand Surgery Society.
There’s disagreement in medical circles, however, on whether repetitive strain is a possible cause.
When symptoms are still minor, the patient is given a splint for the night, which immobilises the wrist.
“This can help but is often felt to be uncomfortable,” Kastrup says.
Surgery is an option, especially if the fingers are constantly numb or the muscles at the base of the thumb – which are moved by signals from the median nerve – have atrophied.
“It’s also a matter of the patient’s tolerance,” Van Schoonhoven says.
At some point, sufferers may grow weary of waking up repeatedly at night.
Carpal tunnel surgery
In open surgery, the band of tissue covering the carpal tunnel is cut, leaving a gap that eventually fills with scar tissue.
“This causes it to lengthen, and relieves pressure on the nerve,” Van Schoonhoven says.
Like any operation, carpal tunnel surgery carries risks.
The nerve can be damaged or – in very rare cases – severed.
This same goes for endoscopic surgery, another option where the surgeon makes a smaller incision than in open surgery.
“Some patients experience pain after endoscopic surgery, during which the nerve is pressed,” Van Schoonhoven says.
After four weeks, however, the results of both open and endoscopic surgery are equally good, he noted.
Both types of surgery are performed on an outpatient basis under a local anaesthetic.
By the time the wound has healed – usually after about two weeks – the symptoms will have typically disappeared.
However, pre-surgery damage to the median nerve or atrophied muscles at the base of the thumb can’t always be reversed.
So symptoms of carpal tunnel syndrome shouldn’t be taken lightly. – dpa/Elena Zelle