Choroid fissure

The choroidal fissure is a narrow, C-shaped cleft in the medial wall of the lateral ventricle along which the tela choroidea and choroid plexus are attached and invaginate into the ventricular cavity. It follows the C-shaped course of the lateral ventricle from the region of the interventricular foramen toward the temporal horn.

In the body of the lateral ventricle, the choroidal fissure lies between the fornix medially and the thalamus/lamina affixa laterally.

As the choroid fissure continues into the temporal horn, its relationships change: it lies principally between the fimbria of the hippocampus inferomedially and the diencephalic/roof attachment superiorly. The choroid plexus of the temporal horn projects into the ventricle through this fissure.

Importantly, the choroidal fissure is not the choroid plexus itself. It is the cleft through which the vascular tela choroidea and its choroid plexus are related to the ventricular cavity. The fissure also provides a natural microsurgical corridor to structures around the lateral and third ventricles.