Neuroradiology
Teaching FileNeuroradiology
Teaching File
Findings:
There is a predominately high attenuation biconvex extraaxial fluid collection in the frontoparietal region. Associated mass effect is present with effacement of the cortical sulci. The overlying calvarium has a defect which is better visualized on the CT at bone window settings; a mildly depressed skull fracture is seen.
90% of epidural hematomas are caused by head trauma with a skull fracture that crosses a portion of the middle meningeal artery or vein. The middle meningeal artery is torn in 60% of cases.
Venous structures--middle meningeal vein, venous sinus or diploic
veins are affected in the rest of cases. Venous epidural hematomas
are most often seen in the pediatric population and are not as
often associated with skull fractures. 
In another patient, there is a high attenuation biconvex extraaxial
fluid collection which crosses the midline and involves both frontal
regions.
Blood which collects in the epidural space is limited by the intracranial sutures, where the dural membrane is closely adherent to the calvarium.
Patients may experience a lucid interval (50%) after injury before further deterioration.
CT reveals a high density extraaxial abnormality that takes on a biconvex (lenticular) shape. MRI performed soon after the injury will show the hemorrhage to be isointense on T1 weighted images and low intensity on T2 weighted images.
Possible complications include pseudoaneurysm of the middle meningeal artery or fistula between the middle meningeal artery and vein.
Case prepared by Steven Lee, M.D. and Anthony L. Alcantara, M.D.
Related case from the University of Alabama at Birmingham Radiology Teaching File