Final answer:
Carpal tunnel syndrome is the cause of the weakness and decreased sensation described. It occurs when the median nerve in the wrist becomes compressed due to inflammation and swelling in the carpal tunnel. Treatment options include wrist splints, corticosteroid injections, and surgery.
Step-by-step explanation:
Weakness of the opponens of the thumb and adduction of the 4th and 5th digits, along with decreased sensation in these digits extending into the palm and ending at the crease of the wrist, are symptoms of carpal tunnel syndrome. Carpal tunnel syndrome occurs when the median nerve in the wrist becomes compressed due to inflammation and swelling in the carpal tunnel.
This compression can be caused by overuse of the wrist muscles or wrist injury. The lack of nervous stimulation by the median nerve can eventually lead to muscle weakness and wasting away in the affected hand muscles.
Treatment for carpal tunnel syndrome may involve wearing a wrist splint, receiving corticosteroid injections, or undergoing surgery to reduce pressure on the median nerve. Without treatment, carpal tunnel syndrome can lead to long-term complications and impair hand function.