The choroidal fissure starts at the posterior edge of the Foramen of Monro as a cleft between the body of the fornix and thalamus. It contains the choroid plexus (CP), which is attached by the tenia fornicis (medial) and tenia thalami (lateral) to the fornix and thalamus, respectively
It ends immediately behind the uncus as the inferior choroidal point, which is inferior and anterior to the entrance point of the choroidal artery and exit of the inferior ventricular vein.
The posterior two-thirds of the medial wall of the temporal horn, posterior to the inferior choroidal point consists of the choroidal fissure.
The choroidal fissure is located between the thalamus and fimbria; it begins at the inferior choroidal point behind the head of the hippocampus and constitutes the medial wall of the posterior two-thirds of the temporal horn 1).
The choroidal fissure is divided into three parts:
(a) a body portion situated in the body of the lateral ventricle between the body of the fornix and the thalamus
(b) an atrial part located in the atrium of the lateral ventricle between the crus of the fornix and the pulvinar
© a temporal part situated in the temporal horn between the fimbria of the fornix and the lower surface of the thalamus.
The three parts of the fissure are the thinnest sites in the wall of the lateral ventricle bordering the basal cisterns and the roof of the third ventricle. Opening through the body portion of the choroidal fissure from the lateral ventricle exposes the velum interpositum and third ventricle. Opening through the temporal portion of the choroidal fissure from the temporal horn exposes the structures in the ambient and crural cisterns. Opening through the atrial portion of the fissure from the atrium exposes the quadrigeminal cistern, the pineal region, and the posterior portion of the ambient cistern 2).
Red arrows: transverse cerebral fissures Green arrows: choroidal fissures
The vascular structures that converge on the choroidal fissure include the thalamostriate vein, anterior/ posterior septal vein, caudate vein and superior choroidal veins, and medial/lateral choroidal arteries. The thalamostriate veins course between the caudate nucleus and the thala- mus and traverse through the posterior margin of the FM to drain into the internal cerebral veins (ICV)