A brain CT showing hypodense shadows is not necessarily a problem. Cerebral infarction, cerebral edema, brain tumor, soft foci left after cerebral hemorrhage and other common causes can lead to low density shadow. 1. Cerebral infarction: Cranial CT in the acute stage of cerebral infarction may have no abnormality, while cranial CT in the chronic stage may show hypodense shadow. 2. Cerebral edema: It shows low-density shadow on cranial CT and needs to be treated with mannitol dehydration to reduce intracranial pressure as prescribed by doctor. 3. Brain tumor: most patients with brain tumors show low-density shadows on cranial CT, and cranial magnetic resonance enhancement examination can further clarify the diagnosis if necessary. 4. Soft foci: soft foci left behind by craniocerebral injury or cerebral hemorrhage will show hypodense shadows in CT, which usually has no effect on patients, and patients can review CT regularly to observe the changes. Cranial CT shows low-density shadow, not necessarily a problem. If there is discomfort, timely consultation, do not be careless, delay treatment.