Numbness of the left thumb involves a very wide range of causes. Considering the numbness symptom alone, there are several common causes: I. Numbness of the thumb occurs as a result of abnormal nerve function due to stimulation by localized adverse factors, including exposure to cold, dampness, and injury. Second, carpal tunnel syndrome, due to the median nerve in the carpal tunnel is compressed, the corresponding thumb numbness. Fracture of the wrist joint, due to the fracture of the wrist joint or inflammation leading to the radial nerve is affected, there will also be numbness of the dorsal side of the thumb. Elderly patients with cerebral infarction or cerebral thrombosis may also experience numbness in the thumb. In addition to consider the numbness symptoms, but also look at other accompanying symptoms for a comprehensive judgment, through a variety of symptoms and the physician’s examination, coupled with auxiliary examination to confirm the diagnosis.