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Study on Microanatomy of the Choroidal Fissure and Transchoroidal Approach

Author: WangYongHeng
Tutor: FengJi
School: Hebei Medical University
Course: Surgery
Keywords: choroidal fissure lateral ventricles third ventricle quadrigeminal cistern ambient cistern microsurgical anatomy operative approach
CLC: R651
Type: Master's thesis
Year: 2009
Downloads: 68
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Abstract

The choroidal fissure is the C-shaped natural cleft between the fornix and the thalamus in the lateral ventricle, and is divided into body, atrial, and temporal parts. Through the choroidal fissure, some deep lesions can be operated without sacrificing the surrounding neural or vascular structures.Objective: Adult cadaveric heads were studied for the microanatomy of the choroidal fissure and the related structures including the lateral ventricle, the third ventricle, the quadrigeminal cistern and the ambient cistern. Simultaneously, the transchoroidal approaches were simulated to enter the third ventricle, the quadrigeminal cistern and the ambient cistern, which provided anatomical basis for treating lesions in such sites.Methods: 10 formalin-fixed normal adult cadaveric heads were performed to observe the structure of the choroidal fissure and the relationship between the choroidal fissure and the lateral ventricle, and while to record the course and distribution characteristics of the vessels which pass though the choroidal fissure. The important anatomical structures and exposed range were recorded under the microscope when the transchoroidal approaches were performed to enter the third ventricle, the quadrigeminal cistern and the ambient cistern. The important structures were measured and recorded, and their photos were taken by camera. SAS8.0 software was used for statistical analysis.Results: The choroidal fissure is located between the fornix and thalamus in the lateral ventricle and extends from the posterior border of the foramen of Monor to the inferior choroidal point which is located behind the hippocampus head in the temporal horn. The total length of the choroidal fissure is 52.7±8.1mm. It can be divided into body, atrial, and temporal parts. The body portion of the fissure, 29.8±5.7mm in length, is located in the body of the lateral ventricle between the body of the fornix and the superior surface of the thalamus. The velum interpositum is located on the medial side of the body portion in the roof of the third ventricle. On the vertical line through the center of the massa intermedia, the distances from the choroidal fissure to the center of the massa intermedia and to the floor of the third ventricle are 13.1±2.9mm and 17.9±3.8mm respectively. The atrial portion of the fissure is located in the atrium of the lateral ventricle between the crus of the fornix and the pulvinar. The distances from the posterior border of the atrial portion of the fissure to initiation point of the fissure and to pineal body are 31.4±3.5mm and 10.8±2.1mm respectively. The temporal portion of the fissure is located in the temporal horn of the lateral ventricle between the fimbria of the fornix and the lower surface of thalamus. The distances from the inferior choroidal point to the posterior border of the atrial portion, to the lateral border of cerebral peduncle in ambient cistern, to superior border of incisure of tentorium of cerebellum are 22.9±4.1mm and 5.7±2.6mm and 10.5±3.5mm respectively.The arteries most intimately related to the choroidal fissure are anterior choroidal artery, medial posterior choroidal artery, and lateral posterior choroidal artery. There are arterial anastomoses in each of the choroidal arteries. The size of the plexal areas supplied by the choroidal arteries is inversely related. The veins most intimately related to the choroidal fissure are those course in the walls of the lateral ventricles, the roof of the third ventricle and the basal cisterns. The ventricular veins are divided into medial and lateral groups. The medial group passes through the forniceal circumference of the fissure, and the lateral group passes through the thalamic circumference of the fissure.Opening through the body portion of the choroidal fissure from the lateral ventricle exposes the third ventricle. Both the tenia fornicis and the tenia choroidea can be opened and expose all of the structures in the third ventricle well. None of the major ventricular veins pass through the tenia fornicis but the thalamocaudate vein passes through tenia choroidea in part of specimens. When incision need to be extended forward, anterior vein of septum pellucidum should be sacrificed when passing through the tenia fornicis and the thalamostriate vein should be sacrificed when passing through the tenia choroidea. To expose the structures in the third ventricle, dissection between the two internal cerebral veins may avoid the veins that come from the upper surface of the thalamus and run medially toward the internal cerebral, while dissection besides the ipsilateral internal cerebral may obtains better exposure of posterior part of the third ventricle without extensive retraction of the internal cerebral.Opening through the atrial portion of the choroidal fissure from the lateral ventricle exposes the quadrigeminal cistern and the posterior part of ambient cistern. Both the tenia fimbriae and the tenia choroidea can be opened. None of the major ventricular veins pass through the tenia fimbriae and the opportunity of damaging the choroidal arteries is minor. Many blood vessels passing though the cisterns, such as posterior cerebral artery (P2 and P3) and basal vein, will be well exposed through atrial portion of choroidal fissure. Pineal body will be exposed after remove these vessels.Opening through the temporal portion of the choroidal fissure from the lateral ventricle exposes the ambient cistern. None of the major ventricular veins pass through the tenia fimbriae. Many blood vessels passing though the ambient cisterns, such as posterior cerebral artery (P2), basal vein and choroidal arteries, will be well exposed through temporal portion of choroidal fissure. The structures in interpeduncular cistern will be exposed after extending the incision forward.Conclutions:1. The choroidal fissure is the natural cleft in the lateral ventricle. Opening through the body, atrial and temporal portion of the choroidal fissure exposes the third ventricle, the quadrigeminal cistern and the ambient cistern respectively, so the choroidal fissure can be used as a natural passageway to cure the lesions in those areas.2. Transchoroidal approach to the third ventricle is used for all kinds of lesions located in the third ventricle, especially those in the posterior portion of the third ventricle and growing unilaterally.3. Transchoroidal approach to the quadrigeminal cistern is used for vascular malformations and vascular lesions around pulvinar and the atrial portion, but lesions in the pineal region should be considered.4. Transchoroidal approach to the ambient cistern is used for arteriovenous malformations of the temporal horn, hippocampus, and medial part of the temporal lobe that are fed by the arteries entering and drained by the veins exiting the choroidal fissure and aneurysm of posterior cerebral artery (P2 segment), and also for tumors in the medial part of the temporal lobe and superior part of the ambient cistern.

Study on Microanatomy of the Choroidal Fissure and Transchoroidal Approach

Abstract

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