Arm numbness and hand numbness, the reason may be physiological, there may be pathological factors such as cervical spondylosis, central nervous system lesions and so on. 1. Physiological reasons: poor sleeping posture can cause tissue compression, blood circulation is limited, the formation of hand and arm numbness, can be relieved by themselves. 2. Pathological causes (1) Cervical spondylosis: localized compression of the cervical intervertebral disc herniation on the nerve root can cause numbness and pain in the arms and hands. (2) Central nervous system lesions: the sudden appearance of hand or arm numbness may be caused by cerebral infarction, cerebral hemorrhage, intracranial tumors, multiple sclerosis and other central nervous system diseases. Patients with arm numbness and hand numbness, if physiological factors are excluded, they should consult a doctor in time to find out the cause and actively treat it.