Numbness of the left side of the face and the left hand may be caused by autonomic dysfunction, cerebrovascular disease, brain tumor, cervical spondylosis and other reasons. 1. Autonomic dysfunction: this disease can lead to neurological dysfunction, dysregulation of the autonomic nervous system, which may show numbness of the left side of the face and the left hand, and may be accompanied by localized itching of the skin, dizziness, panic and other symptoms. 2. Cerebrovascular disease: commonly seen in cerebral hemorrhage, cerebral infarction, etc., due to the symptoms of ischemia or hemorrhage in the local brain tissue, resulting in local brain nerve compression and damage, there may be numbness in the left side of the face and the left hand, accompanied by symptoms of neurological deficit such as unfavorable speech, difficulty in swallowing, and so on. 3. Brain tumor: the increase of tumor volume leads to local brain tissue pressure, resulting in damage to the brain nerves in the pressure area, which may cause numbness of the left side of the face and the left hand, and may be accompanied by severe headache, as well as nausea, vomiting and other symptoms. 4. Cervical spondylosis: Cervical spondylosis can lead to degeneration of the intervertebral joints, and the degenerated tissues can compress or stimulate the adjacent spinal cord and nerve roots, making the patient experience sensory disturbances and causing numbness in the left hand and face. Numbness of the left hand and face may also be related to other factors, if the symptoms continue to be unable to alleviate, it should be taken seriously, as soon as possible to the regular hospital, through the improvement of the relevant examination, diagnosis of the causal factors, by the doctor’s guidance for treatment.