Carpal tunnel syndrome is the result of swelling and inflammation in the carpal tunnel, a narrow channel between bones and ligaments within the wrist through which a major nerve passes. Called the median nerve, this nerve and its branches provide feeling to the thumb, index finger, long finger, and half of the ring finger. Additionally, it provides strength to the thumb and portions of the index and long fingers. When the space in the carpal tunnel decreases, the median nerve becomes squeezed, and a person may feel numbness and/or tingling and eventually weakness in the thumb and associated fingers.