In subfalcine herniation, brain tissue is pressed against which dural structure?

• A. Falx cerebri
• B. Tentorium cerebelli
• C. Dura mater overlying the skull
• D. Arachnoid mater

Answer: (A)

Subfalcine herniation involves a midline shift where brain tissue is pushed under a dural fold that separates the two cerebral hemispheres. The falx cerebri is that sickle-shaped fold of dura mater running in the longitudinal fissure. When intracranial pressure rises, the medial part of a hemisphere, the cingulate gyrus, can herniate beneath the edge of the falx cerebri, so the tissue ends up pressed against the falx itself. This specific barrier—the falx cerebri—defines subfalcine herniation. The other structures mentioned don’t form the barrier involved in this pattern: the tentorium cerebelli lies horizontally to separate cerebrum from cerebellum (relating to transtentorial herniation), the dura mater over the skull is the periosteal layer, and the arachnoid mater is the middle meninx, not the structure the brain is pressed against in this scenario.