Patchy abnormal signal in the left frontal lobe is often not self-healing, and common causes include cerebral infarction, demyelinating disease, and intracranial space-occupying lesions. 1. Cerebral infarction: When cerebral infarction occurs, the left frontal lobe patchy abnormal signal can be seen on CT or MRI. When cerebral infarction occurs, it is very difficult to be cured by itself, and if the treatment is not timely, serious neurological damage may occur, and sequelae may occur. 2. Demyelinating diseases: common causes include multiple sclerosis, optic neuromyelitis optica and so on. The onset of limb weakness, sensory impairment, etc., often can not be self-healing, if the treatment is not timely aggravation of the condition can lead to limb motor dysfunction, visual impairment and other hazards. 3. Intracranial space-occupying lesions: intracranial space-occupying tumors can be manifested as patchy abnormal signals in the left frontal lobe, which usually will not be cured on its own, and if it is not treated in time, the tumor will continue to increase, leading to increased cranial pressure, and even causing brain hernia and thus endangering the lives of the patients. There are other reasons for left frontal lobe patchy shadow, it is recommended to go to the regular hospital in time, under the guidance of professional physicians to clarify the cause of the disease, and actively diagnosis and treatment.