Why do flashes of light and black spots appear in front of my eyes before a headache attack?

　　+Why do flashes of light and black dots appear in front of my eyes before a headache attack?　　In about a quarter of migraine patients, the headache is preceded by a number of aura symptoms. The visual aura is the most common, lasting from a few minutes to an hour. In addition to the visual aura, some patients also experience other physical discomfort, such as numbness of the hemiplegia and speech disturbances. This phenomenon occurs due to a change in the visual cortex of the brain called cortical spreading inhibition prior to the headache, resulting in abnormal stimulation and inhibition changes in the higher centers of the brain that manage vision, causing the patient to experience illusions such as flashes of light in front of the eyes, and after this illusion occurs, a more intense headache often begins!