Table of Contents

Choroidal fissure

The choroidal fissure, or choroid fissure, is a cleft of the medial surface of the cerebral hemisphere running immediately above the hippocampus and forms the medial wall of the lateral ventricle and attachment site for the choroid plexus.

Gross anatomy

The C-shaped fissure runs between the fornix (body, crus, and fimbria) and the thalamus. At the level of the hippocampus, the choroidal fissure is a lateral extension of the transverse fissure of Bichat, which in turn is a lateral extension of the ambient cistern 1) 2).

The choroid plexus originates at the inferior choroidal point of the choroidal fissure, which is located just posterior to the hippocampal head. At this location, the anterior choroidal artery enters the temporal horn of the lateral ventricle. Only choroid plexus and a thin arachnoid membrane separate the cerebrospinal fluid space of the choroidal fissure and the lateral ventricle.

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

In the temporal horn, the choroidal fissure is located between the stria terminalis of the thalamus superomedially and the fimbria inferolaterally.

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 3).

Importance

see Transforaminal transchoroidal endoscopic colloid cyst resection

It is one of the most valuable anatomic landmarks a neurosurgeon can rely on during temporal lobe surgery.

The site of attachment of the choroid plexus in the lateral ventricle, is located between the fornix and thalamus in the medial part of the lateral ventricle.

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 4).

www.med.wayne.edu_diagradiology_the_20ct_20anatomy_20tutor_ppt2-11_20transverse_20cerebral_20fissure.jpg

Red arrows: transverse cerebral fissures Green arrows: choroidal fissures

http://www.med.wayne.edu/diagradiology/The%20CT%20Anatomy%20Tutor/Brain%20-%20Question%201.html

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)

1)
Holodny AI, George AE, Golomb J, de Leon MJ, Kalnin AJ. The perihippocampal fissures: normal anatomy and disease states. Radiographics. 1998 May-Jun;18(3):653-65. doi: 10.1148/radiographics.18.3.9599389. PMID: 9599389.
2)
Dekeyzer S, De Kock I, Nikoubashman O, Vanden Bossche S, Van Eetvelde R, De Groote J, Acou M, Wiesmann M, Deblaere K, Achten E. “Unforgettable” - a pictorial essay on anatomy and pathology of the hippocampus. Insights Imaging. 2017 Apr;8(2):199-212. doi: 10.1007/s13244-016-0541-2. Epub 2017 Jan 20. PMID: 28108955; PMCID: PMC5359145.
3)
Wen HT, Rhoton AL Jr, de Oliveira E, Cardoso AC, Tedeschi H, Baccanelli M, Marino R Jr. Microsurgical anatomy of the temporal lobe: part 1: mesial temporal lobe anatomy and its vascular relationships as applied to amygdalohippocampectomy. Neurosurgery. 1999 Sep;45(3):549-91; discussion 591-2. PubMed PMID: 10493377.
4)
Nagata S, Rhoton AL Jr, Barry M. Microsurgical anatomy of the choroidal fissure. Surg Neurol. 1988 Jul;30(1):3-59. PubMed PMID: 3394010.