A 25-year-old man sustains head trauma in a road traffic accident. Non-contrast CT head shows a biconvex (lentiform) hyperdense extra-axial collection over the right frontoparietal convexity that stops abruptly at the coronal suture. Which feature explains this limitation of the collection?

• A The blood lies between dura and arachnoid, which are tightly fused at sutures
• B The arachnoid granulations absorb blood at suture lines
• C The tentorium cerebelli blocks centrifugal spread of blood
• D The blood is confined between the periosteal and meningeal layers of dura, which are firmly attached at cranial sutures ✓

Explanation

Epidural hematoma is arterial (middle meningeal artery) blood dissecting between the inner table and the periosteal layer of dura. The periosteal dural layer is continuous with the periosteum and firmly anchored at cranial sutures, so the collection cannot cross sutures and appears biconvex. Subdural blood lies in the potential space between dura and arachnoid and crosses sutures freely, giving a crescentic shape.

Reference: Gray's Anatomy for Students, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.