A 68-year-old man with chronic alcoholism and cerebral atrophy presents to the emergency department 5 days after a minor fall from standing height. CT head shows a crescent-shaped hyperdense collection crossing cranial sutures, as marked **A** in the diagram. Which of the following best describes the mechanism of injury and the vascular structure responsible for this hemorrhage?

Question

Accepted Answer

A. Acceleration-deceleration injury causing tearing of bridging cortical veins crossing from cortex to dural sinuses. ## Why option 1 is correct

The crescent-shaped hyperdense collection marked **A** that crosses cranial sutures is the hallmark CT appearance of acute subdural hematoma (SDH). According to the Brain Trauma Foundation Guidelines and Greenberg Handbook, acute SDH results from bleeding into the potential space between the dura mater and arachnoid mater, classically caused by tearing of bridging cortical veins as they traverse from the cortex to the dural sinuses. In elderly patients with cerebral atrophy (as in this case), even minor head trauma from a fall can produce disproportionate stretching and tearing of these fragile bridging veins due to increased subdural space. The acceleration-deceleration mechanism is the pathophysiologic basis for this injury pattern.

## Why each distractor is wrong

- **Option 2 (Middle meningeal artery laceration)**: This is the classic mechanism of epidural hematoma, not subdural hematoma. Epidural bleeds present as biconvex (lens-shaped) collections limited by sutures (marked **B** in the diagram), not crescent-shaped collections crossing sutures.

- **Option 3 (Aneurysm rupture)**: Aneurysmal rupture causes subarachnoid hemorrhage (blood in the sulci and basal cisterns, marked **D**), not subdural hematoma. The location and imaging appearance are distinctly different.

- **Option 4 (Superior sagittal sinus occlusion)**: While venous pathology can cause intracranial bleeding, sinus occlusion typically causes venous infarction and parenchymal hemorrhage, not the characteristic crescent-shaped extra-axial collection seen with bridging vein injury.

**High-Yield:** Crescent-shaped, crosses sutures = subdural (bridging veins); biconvex, limited by sutures = epidural (meningeal artery).

[cite: Brain Trauma Foundation Guidelines 4th Edition; Greenberg Handbook of Neurosurgery]

Answer

B. Venous occlusion of the superior sagittal sinus leading to venous congestion and bleeding

Answer

C. Direct laceration of the middle meningeal artery from temporal bone fracture

Answer

D. Rupture of an aneurysm in the Circle of Willis with extension into the subdural space

Explanation

Why option 1 is correct

Why each distractor is wrong

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