Numbness and weakness in the patient’s left hand and left foot are considered to be caused by the following three major diseases: First, cerebral infarction, which is caused by the sudden interruption of blood flow to the patient’s brain due to various reasons, causing localized ischemia, hypoxia, and necrosis of brain tissue and the formation of corresponding neurological deficit symptoms. The lesion site that causes numbness and weakness in the patient’s left hand and left foot is considered to be in the right internal capsule or the right brainstem. Second, cerebral hemorrhage, cerebral hemorrhage refers to non-traumatic brain parenchymal hemorrhage, which has a relatively high rate of disability and death. If the patient suddenly develops symptoms of numbness and weakness in the left hand and left foot during emotional excitement or activity, it is considered to be caused by cerebral hemorrhage. Because the patient’s intracranial pressure is increased, it is usually accompanied by headache, nausea, vomiting and other symptoms. If the numbness and weakness of the left hand and left foot appear slowly and gradually progress and worsen, it is considered to be caused by intracranial tumor or intracranial occupancy of the right cerebral hemisphere.