Numbness in the left hand may be caused by cervical spondylosis, as well as small cerebral infarction on the right side, a small amount of cerebral hemorrhage, etc., as follows: 1. cervical spondylosis: such as cervical disc protrusion, compression of local nerves may appear on one side of the hand numbness, at the same time may appear neck, shoulder muscle pain and discomfort, some patients may also appear pain in the back of the head area, should check the cervical spine nuclear magnetic to clarify the diagnosis. 2. small area on the right side Cerebral infarction, a small amount of cerebral hemorrhage: numbness in the left hand may also occur, and is more common in middle-aged and elderly people, who should check the cranial CT or cranial MRI to make a clear diagnosis. If the symptoms of hand numbness are severe, some nerve-nourishing drugs can be used.