The numbness of the left side of the tongue is considered to be caused by intracranial vascular infarction, cervical spondylosis, peripheral neuritis, hyperlipidemia and other reasons, the specific causes of the disease to go to the hospital in time to confirm the examination. 1. Intracranial vascular infarction: when the blood circulation in the brain is ischemic, hypoxia, etc., so that the brain tissue has limited ischemic necrosis, causing the sensory nerve function of the tongue to be dysfunctional, which leads to numbness on the left side of the tongue. 2. Cervical spondylosis: If you suffer from cervical spondylosis, the vertebral artery protruding from the body will compress the nerve root, causing the body to have obstacles, which can lead to the symptoms of numbness on the left side of the tongue. 3. Peripheral neuritis: it is due to a variety of factors leading to damage to the nerve endings, causing symmetrical numbness, tingling and other sensory abnormalities in the distal limbs, which can lead to symptoms of numbness on the left side of the tongue. 4. Hyperlipidemia: when hyperlipidemia occurs, it will make the blood viscosity increase, make the circulation speed in the blood vessel decrease, cause the local tissue blood supply is insufficient, which will lead to the symptoms of numbness on the left side of the tongue. When the symptoms appear, you should go to the hospital in time for examination, to clarify the cause of the disease, under the guidance of professional doctors combined with their own situation for targeted treatment.