Numbness of the left limb is mainly considered to have acute cerebral infarction or cerebral hemorrhage, as well as intracranial tumors, metastases, demyelinating lesions, and functional factors, as follows: First, acute cerebral infarction or cerebral hemorrhage: If the patient has acute left limb numbness and hypertension or diabetes, a cranial magnetic resonance examination should be performed to understand whether there is acute cerebral infarction or cerebral hemorrhage. Second, intracranial tumors, metastases: If chronic left-sided limb numbness, ask the patient if there is weakness of the limbs, and also perform cranial MRI to find out if there are intracranial tumors or intracranial metastases. Third, demyelinating lesions: patients with left-sided limb numbness, if there are recurrent episodes, along with limb weakness and dizziness, should also undergo cranial magnetic resonance examination to understand whether there are demyelinating lesions, and electromyography examination. Fourth, functional factors: numbness of the left limb, if it is a neutral symptom, ask the patient whether there is emotional instability, irritability or depression, also consider the presence of functional factors.