Epidural hematoma is a hematoma located between the inner plate of the skull and the dura mater, which is usually found on the convex surface of the supratentorial hemisphere, with the most frontotemporal and parietotemporal areas, and is closely related to skull injury. CT manifestation: most of them have typical features, with biconvex or shuttle-shaped high-density shadow with clear edges below the inner plate of the skull, with CT value of 40HU-100HU; some hematomas are seen with small round or irregular-shaped low-density areas, which are thought to be caused by fresh bleeding (lower density than that of clotted blood) still present in too short a time of trauma and mixed with the serum spilled during the retreat of the clot. A few hematomas may be semilunar or crescentic in shape; individual hematomas may leak under the extracranial soft tissues through the separated fracture gap; bone windows: often reveal fractures. In addition, the hematoma may show a dominant effect, displacement of midline structures, and compression, deformation, and displacement of the lateral ventricle of the lesion. In chronic epidural hematomas, the hematoma may dissolve on CT scan and appear as a slightly dense or hypodense area. In a small number of patients who are asymptomatic at the time of injury and later develop a delayed, chronic epidural hematoma, enhanced scans may reveal an enhancement of the envelope at the edge of the hematoma, contributing to the diagnosis of an isointense epidural hematoma. MRI manifestations: the site of hematoma occurrence is mostly located at the location of direct violence, mostly with local fractures, not beyond the limits of the cranial suture, and corresponding scalp hematoma. The morphological changes of the epidural hematoma are similar to those of CT. The hematoma is biconvex or pyknotic in shape with sharp borders and is located between the inner plate of the skull and the brain surface. The signal intensity of the hematoma changes in relation to the temporal variation of the hematoma. In the acute phase, on T1-weighted images, the hematoma signal resembles that of the brain parenchyma. In T2-weighted images the hematoma appears as a low signal. In the subacute phase, it appears as high signal in both T1- and T2-weighted images. In the chronic phase, the hematoma may be resorbed or softened or cystic, with low signal on T-weighted images and high signal on T2-weighted images; in addition, due to the occupational effect of the hematoma, the adjacent cerebral cortex on the affected side is compressed and the distance to the inner edge of the skull increases, suggesting signs of extracerebral occupational lesions and leading to a more definite diagnosis.