Epidural hematoma on CT is typically described as which shape?

Epidural hematoma on CT is typically described as which shape?

• A. Crescent-shaped
• B. Biconvex (lens-shaped)
• C. Diffuse low-density
• D. Subarachnoid

Answer: (B)

Epidural hematomas are best recognized on CT by a lens-shaped, biconvex collection of blood between the skull and the dura. This shape comes from blood accumulating as an arterial bleed (often the middle meningeal artery) that pushes the dura inward from both sides. The dura’s firm attachment to the skull at suture lines helps confine it into a discrete, convex-on-both-sides mass, giving the characteristic lens appearance. In contrast, a crescent-shaped collection is typical of a subdural hematoma, which spreads along the brain surface and can cross sutures. Diffuse low-density changes describe global brain edema or chronic changes, not a discrete mass. Blood in the subarachnoid space appears within the sulci and cisterns, not as a separate hematoma mass.

Epidural hematomas are best recognized on CT by a lens-shaped, biconvex collection of blood between the skull and the dura. This shape comes from blood accumulating as an arterial bleed (often the middle meningeal artery) that pushes the dura inward from both sides. The dura’s firm attachment to the skull at suture lines helps confine it into a discrete, convex-on-both-sides mass, giving the characteristic lens appearance.

In contrast, a crescent-shaped collection is typical of a subdural hematoma, which spreads along the brain surface and can cross sutures. Diffuse low-density changes describe global brain edema or chronic changes, not a discrete mass. Blood in the subarachnoid space appears within the sulci and cisterns, not as a separate hematoma mass.