Soft foci is a descriptive imaging term that can be observed on cranial CT or cranial MRI. They can occur secondary to any neurological disease, mainly substantial brain cell damage, and may be followed by soft foci, most commonly after various types of cerebrovascular disease, encephalitis, and brain tumor surgery. Take cerebrovascular disease as an example, soft foci can appear after cerebral infarction and cerebral hemorrhage, when cerebral infarction and cerebral hemorrhage cause brain cells to be destroyed, liquefaction and necrosis will be gradually absorbed by the surrounding tissues, and a cavity will be formed at the original place, and after that, glial cells will proliferate and gradually fill up the cavity to form scar tissues, which will be shown as soft foci on CT or MRI, suggesting that it is a non-acute old lesion. However, if the soft foci persist for a long time, there is a possibility of secondary epilepsy.