True carpal tunnel is caused by a compression of the median nerve due to a structural problem, meaning that something is pushing on the nerve.  This can be due to arthritis, a trauma or injury to the wrist, or a congenital malformation of the area.  Most commonly the symptoms of carpal tunnel syndrome are due to repetitive strain, or overuse, of the wrist and hand area.  The frequent use of the wrist and hand without stretching irritates the local area causing inflammation.