Choroidal fissure [Neurosurgery Wiki]

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====== Choroidal fissure ======

{{::choroidal_fissure.jpg?400|}}

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]] 
((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.))
((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.)).
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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]]
(( 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.
)).

===== Importance =====
see [[Transforaminal transchoroidal endoscopic colloid cyst resection]]
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It is one of the most valuable anatomic [[landmark]]s 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

(c) 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 ((Nagata S, Rhoton AL Jr, Barry M. Microsurgical anatomy of the choroidal
fissure. Surg Neurol. 1988 Jul;30(1):3-59. PubMed PMID: 3394010.)).

{{http://www.med.wayne.edu/diagradiology/The%20CT%20Anatomy%20Tutor/PPT2-11%20Transverse%20Cerebral%20Fissure.jpg?400}}

Red arrows: transverse cerebral fissures
Green arrows: choroidal fissures

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