If suddenly appear left leg, left arm weak symptoms, consider acute cerebrovascular disease, such as transient ischemic attack, cerebral infarction and cerebral hemorrhage and other diseases, will lead to the patient to appear side limb weakness. 1, general left body weak, soft, consider the right hemisphere or the right side of the brain bridge lesions caused by the right hemisphere of the brain is generally the location of the internal capsule, the director of the motor nerve. The patient’s motor nerves, when there is a problem, there will be no strength in the left arm and leg. The patient’s left leg and left arm have no strength and softness; 2. If it appears slowly and progresses gradually, it is considered that it is caused by intracranial tumor occupying and compressing, and the site of the tumor should be in the right hemisphere, which can be clarified by head CT and magnetic resonance imaging (MRI).