The following clinical conditions can cause frequent pain in the left side of the brain: 1, caused by high blood pressure, when the body has high blood pressure, the elevated blood pressure can have a strong impact on the cerebral blood vessels, or produce a certain expansion and compression of the cerebral blood vessels. The brain is rich in nerve distribution, so the expansion of the cerebral vessels can lead to the nerves on the vessels are strained and stimulated, thus causing pain in the left side of the brain. 2, may also be due to brain aneurysm or brain embolism, etc. When there is a brain aneurysm or brain embolism, the blood circulation of the lesion will be impaired, causing blood blockage, resulting in ischemia and hypoxia of brain cells in the lesion, leading to The aneurysm or embolized blood vessel may also compress the normal brain nerve and cause pain in the left side of the brain.