The space between the leaves of the septum pellucidum is called which of the following?

• A. Cavum septum pellucidi
• B. Falx cerebri
• C. Corpus callosum
• D. Interhemispheric fissure

Answer: (A)

The space between the two leaflets of the septum pellucidum is called cavum septum pellucidi. The septum pellucidum is a thin, double membrane that separates the anterior horns of the lateral ventricles, and the gap between these leaves forms a potential cavity known as CSP. In normal development this space often closes with age, but it can be seen in fetal or neonatal imaging.

The other structures are not the space between the leaves of the septum pellucidum: the falx cerebri is a dural fold within the interhemispheric fissure that helps separate the two cerebral hemispheres; the corpus callosum is the broad bundle of nerve fibers connecting the hemispheres; and the interhemispheric fissure is the long groove between the hemispheres that contains the falx and other midline structures, not specifically the space between the septal leaves.