General
- The choroidal fissure is found in the lateral ventricle
- Forming a C-shaped arc that parallels the fornix.
Extension
- Rostrally (Anteriorly): Beginning at the foramen of Monro.
- Through the Ventricle: Continuing through the body, atrium, and temporal horn of the lateral ventricle.
- Surrounding the superior, inferior, and posterior surfaces of the thalamus.
- Caudally (Inferiorly): Terminating at the inferior choroidal point, which is located just behind the head of the hippocampus.
- Inferior choroidal poin
- The inferior termination of the choroidal fissure
- Located
- Immediately behind the uncus
- Below and slightly anterior to the lateral geniculate body of the thalamus
- Vessels enter and exit
- Anterior to the site where the anterior choroidal artery enters the temporal horn
- Inferior ventricular vein exits the temporal horn to join the basal vein of Rosenthal
Borders
- The fissure represents a natural cleavage plane and anatomical boundary between two major deep structures of the cerebrum, which form its margins:
- Outer Margin (Forniceal Side): Formed by the components of the fornix.
- In the body of the ventricle, the outer edge is formed by the body of the fornix.
- In the atrium, it is formed by the crus of the fornix.
- In the temporal horn, it is formed by the fimbria of the fornix.
- Inner Margin (Thalamic Side): Formed by the thalamus.
- In the body portion, it is bounded inferiorly by the superior surface of the thalamus.
- In the atrial part, it is bounded anteriorly by the pulvinar (part of the thalamus).
- In the temporal horn, it is bounded superiorly by the stria terminalis and the inferolateral surface of the thalamus.
Embryonic Development
- The fissure is formed at approximately eight weeks of embryonic development when the vascular pia mater that forms the epithelial roof of the third ventricle invaginates into the medial wall of the cerebral hemisphere.
Anatomical Subdivisions
- Based on the area of the lateral ventricle they border:
- Body Part:
- Located in the body of the lateral ventricle, between the body of the fornix and the thalamus (superior surface).
- Opening the body portion exposes the velum interpositum and the roof of the third ventricle.
- Atrial Part:
- Located in the atrium, between the crus of the fornix and the pulvinar.
- Opening the atrial part exposes the quadrigeminal cistern and the pineal region.
- Temporal Part:
- Located in the temporal horn, between the fimbria of the fornix and the inferolateral surface of the thalamus.
- Opening the temporal part exposes the structures in the ambient and posterior part of the crural cisterns.
Significance and Function
- Choroid Plexus Attachment:
- It is the cleft along which the choroid plexus of the lateral ventricle is attached.
- The choroid plexus arises from the tela choroidea, and the fissure is bordered by small ridges along the fornix and thalamus, called teniae, where the membrane (tela choroidea) attaches.
- Thinnest Ventricular Wall:
- It is the thinnest site in the wall of the lateral ventricle because no nervous tissue develops between the ependyma and pia mater along this invagination.
- Yellow: The cavity of the temporal horn
- Green: The ependymal covering
- Red: Pia mater
- Note that the choroid plexus is covered by pia mater and ependyma.
- The taenia choroidea and taenia fimbriae are ependymal covering that attaches the choroid plexus to the thalamus and to the fimbria, respectively.
- 1, Choroid plexus;
- 2, Fimbria;
- 3, Hippocampus;
- 4, Hippocampal sulcus (between the dentate gyrus superiorly and the parahippocampal gyrus inferiorly);
- 5, Brainstem;
- 6, Occipitotemporal sulcus;
- 7, Collateral sulcus;
- 8, Parahippocampal gyrus;
- 9, Inferior temporal gyrus;
- 10, Fusiform gyrus.
Images
- Vascular Passage: It serves as a crucial passage for major vessels:
- Arteries: The choroidal arteries (Anterior Choroidal Artery (AChA) and Posterior Choroidal Arteries (PChAs)) that supply the choroid plexus arise in the basal cisterns and enter the ventricles by passing through the choroidal fissure. For example, the AChA enters the temporal horn by passing through the inferior choroidal point at the lower end of the fissure.
- Veins: The ventricular veins that drain the walls of the lateral ventricles (including the internal capsule, basal ganglia, and thalamus) exit the ventricles by passing through the margin of the fissure in a subependymal location to reach the internal cerebral, basal, or great veins. This convergence of ventricular veins on the fissure aids in identifying its location during surgery.
Images
1, Internal carotid artery;
2, Anterior cerebral artery;
3, Anterior segment of the uncus;
4, Optic tract and oculomotor nerve;
5, Basal vein (first or striate segment) and anterior choroidal artery (cisternal segment);
6, Amygdala;
7, Peduncular vein and posterior perforated substance;
8, Basal vein (peduncular segment);
9, Inferior choroidal point, inferior ventricular vein, and anterior choroidal artery (plexal segment);
10, Lateral geniculate body;
11, Pulvinar of the thalamus,
12, Splenium of the corpus callosum;
13, Vein of Galen;
14, Lingual gyrus.
- Surgical anatomy
- The choroidal fissure is one of the most important landmarks in microneurosurgery involving the body, third ventricle, and temporal lobe. (see anatomical subdivisions)
- Most valuable anatomic landmarks that a neurosurgeon can count on during surgical procedures.
- The choroidal fissure of the temporal horn is easily identified by following the choroid plexus in the medial aspect of the temporal horn;
- All structures located laterally to the choroid plexus belong to the temporal lobe and can be removed, and all structures located medially to the choroidal fissure in the temporal horn belong to the thalamus and should not be harmed.
- Opening the choroidal fissure in the temporal horn leads to the contents of the ambient cistern.
Stepwise dissection from the Lateral ventricle → 3rd → Choroidal fissure →Basal cistern
A., artery; Ant., anterior; Bas., basilar; Call., callosum; Caud., caudate; Cer., cerebral; Ch., choroidal; Chiasm., chiasmatic; Chor., choroid; Col., column; Coll., colliculus; Comm., commissure; Corp., corpus; CN, cranial nerve; For., foramen; Front., frontal; Gen., geniculate; Infund., infundibular; Int., intermedia, internal; Lam., lamina; Lat., lateral; Mam., mamillary; M.P.Ch.A., medial posterior choroidal artery; Nucl., nucleus; P.C.A., posterior cerebral artery; Pell., pellucidum; Plex., plexus; Rec., recess; Sept., septal, septum; Tent., tentorial; Term., terminalis; Thal. Str., thalamostriate; V., vein; Vent., ventricle
- Superior view of the lateral ventricles.
- The choroidal fissure is the cleft between the fornix and the thalamus along which the choroid plexus is attached. The frontal horn is located anterior and the ventricular body behind the foramen of Monro.
- The thalamus forms the floor of the body of the lateral ventricle and the anterior wall of the atrium
- Enlarged view.
- The columns of the fornix form the anterior and superior margins of the foramen of Monro.
- The choroid plexus in the body extends through the posterior margin of the foramen of Monro and is continuous with the choroid plexus in the roof of the third ventricle.
- The right thalamostriate vein passes through the posterior edge of the foramen of Monro and the left thalamostriate vein passes through the choroidal fissure behind the foramen.
- Floor of the frontal horn rostrum of the corpus callosum
- Anterior wall is formed by the genu of the corpus callosum.
- Lateral wall is formed by the caudate nucleus.
- The septum pellucidum is attached to the upper edge of the body of the fornix.
- Enlarged view of the right foramen of Monro.
- The columns of the fornix form the anterior and superior margins of the foramen.
- An anterior septal vein passes backward along the septum pellucidum and crosses the column of the fornix.
- The thalamostriate vein passes forward between the caudate nucleus and thalamus and turns medially to pass through the posterior margin of the foramen of Monro to empty into the internal cerebral vein.
- The choroid plexus is attached medially by the tenia fornix to the body of the fornix and laterally by the tenia thalami to the thalamus.
- The transchoroidal exposure is begun by dividing the tenia fornix that attaches the choroid plexus to the margin of the fornix.
- The tenia thalami that attaches the choroid plexus to the thalamus is not opened.
- The opening of the choroidal fissure has been extended backward from the foramen of Monro to expose both internal cerebral veins and the medial posterior choroidal arteries coursing in the velum interpositum.
- The anterior septal vein crosses the septum pellucidum.
- The lower layer of tela choroidea, attached to the striae medullaris thalami deep to the internal cerebral veins, is intact.
The lower layer of tela choroidea that forms the floor of the velum interpositum has been opened, exposing the massa intermedia and posterior commissure within the third ventricle.
The internal cerebral veins have been separated to expose the anteroinferior part of the third ventricle.
The upper end of the midbrain forms the posterior part of the floor of the third ventricle
The mamillary bodies are situated in the midportion of the floor.
The floor anterior to the mamillary bodies and behind the infundibular recess in very thin and is the site commonly opened in a third ventriculostomy.
The chiasmatic recess extends forward above the posterior edge of the optic chiasm and below the anterior commissure
Enlarged view of the inner surface of the anterior wall of the third ventricle.
The columns of the fornix extend downward behind the anterior commissure toward the mamillary bodies.
The lamina terminalis, chiasmatic recess, posterior edge of the chiasm, and the infundibular recess are located along the anterior and lower wall of the third ventricle
The opening along the choroidal fissure has been extended posteriorly by opening the tenia fornix along the edge of the body and crus of the fornix.
The upper part of the quadrigeminal cistern, where the internal cerebral veins converge on the vein of Galen, has been exposed.
The medial posterior choroidal arteries course with the internal cerebral veins
The opening of the choroidal fissure has been extended downward along the choroidal fissure to the central part of the quadrigeminal cistern, exposing the basal and internal cerebral veins, pineal, and superior colliculus. Branches of the medial posterior choroidal arteries course beside the pineal.
Enlarged view. The tip of the pineal projects posteriorly above the superior colliculus and between the terminal part of the internal cerebral veins.
The dissection has been extended forward along the choroidal fissure toward the temporal horn by dividing the tenia on the edge of the fimbria of the fornix to expose the basal vein, posterior cerebral arteries, and trochlear nerve in the posterior part of the ambient cistern below the thalamus
The choroidal fissure in the temporal horn has been opened by dividing the tenia fimbria. The choroid plexus attachment to the thalamus has not been disturbed. The posterior cerebral artery and basal vein course through the ambient cistern on the medial side of the temporal portion of the choroidal fissure.
The exposure has been extended through the amygdala anterior to the choroidal fissure to expose the oculomotor nerve and origin of the posterior cerebral artery. The posterior cerebral artery passes above the oculomotor nerve.
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