FIGURE 113.1 Traumatic subdural hemorrhage Axial noncontrast CT shows a significant 6-mm SDH over the left hemispheric convexity with approximately mm of midline shift In contrast, the vascular injury causing epidural hemorrhage, typically the middle meningeal artery or dural venous sinus, allows blood to transverse the space between the dura and overlying bony surface The accumulating epidural blood is not able to transverse the dural attachments at the sutures accounting for the lens-shaped biconvex appearance on radiographic imaging ( Fig 113.2 ) Venous bleeding may accumulate slowly and account for the classic presentation of patients with epidural hematomas with a period of lucidity followed by rapid clinical deterioration