Which is the largest dural fold that separates the cerebrum into left and right hemispheres along the longitudinal fissure?

• A. Dural Folds
• B. Tentorium Cerebelli
• C. Foramen of Monro
• D. Falx Cerebri

Answer: (D)

The key idea is that dural folds form partitions inside the skull, and the one that sits between the two cerebral hemispheres in the longitudinal fissure is the falx cerebri. This fold of dura mater is the largest and descends like a sickle into the fissure, separating the left and right hemispheres. It attaches anteriorly to the crista galli of the ethmoid bone and posteriorly to the internal occipital crest, with its margins forming the superior and inferior sagittal sinuses. This arrangement helps stabilize the brain and maintain the separation between hemispheres. In contrast, the tentorium cerebelli sits higher up, forming a tent-like shelf that partitions the cerebrum from the cerebellum, and the foramen of Monro is simply an opening for CSF flow between ventricles, not a dural fold.