When patients have left hand numbness, it may be related to cervical spine lesions, brain lesions and neurological diseases. 1. Cervical spine lesion: When patients have cervical spine lesion, it leads to the compression of hand nerves, thus patients have left hand numbness, common cervical spine lesions include radicular cervical spondylosis, vertebral artery cervical spondylosis, spinal cord cervical spondylosis and so on. 2. Brain lesions: when the patient suffers from stroke, cerebral infarction and other brain diseases, due to blood circulation in the brain, ischemia, hypoxia caused by ischemic necrosis or softening of limited brain tissue, may cause numbness in the left hand. 3. Neuropathy: Carpal tunnel syndrome, multiple peripheral neuritis and other neuropathies may also lead to numbness of the left hand. In addition, heavy metal poisoning, alcoholism and other causes may also cause numbness in the left hand, it is recommended that the patient consult a doctor in a timely manner for examination to clarify the cause of targeted treatment.