The patchy hypointense shadow in the brain is most commonly caused by cerebral infarction, and whether it is serious or not depends on the patient’s condition. If the patient has sudden problems such as inflexible limb movement or sensory numbness, and patchy hypointense shadow is seen on the head CT, it indicates that the patient is in the acute stage of cerebrovascular disease and needs active treatment, which is more serious because once the condition progresses and worsens, it may lead to limb paralysis, unfavorable speech or complete aphasia. If the patient is asymptomatic and has patchy hypointense shadow, it is considered to be a manifestation of old lacunar cerebral infarction or other such as cerebral hemorrhage sequelae in recovery. For patchy hypointense shadow, if it is symmetrical in the lateral ventricle, demyelination is considered, which is a subcortical atherosclerotic encephalopathy caused by intracerebral ischemia, and the patient should control the degree of cerebral atherosclerosis to reduce the demyelination of the brain.