TRANSCHOROIDAL APPROACH TO THE 3RD-VENTRICLE - AN ANATOMIC STUDY OF THE CHOROIDAL FISSURE AND ITS CLINICAL-APPLICATION

OBJECTIVE: We review the anatomic features of the lateral ventricle, t he foramen of Monro, the third ventricle, and the choroidal fissure, a nd we describe the transchoroidal approach to the third ventricle. Thi s approach consists of opening the taenia fornicis of the choroidal fi ssure in the body of the lateral ventricle and approaching the third v entricle between the two internal cerebral veins. This route allows fu rther posterior enlargement of the foramen of Monro without sacrificin g any neural structures, When necessary, the anterior septal vein can be sacrificed. METHODS: Twenty adult cadaveric brains and four adult c adaveric heads were studied, using a magnification ranging from 3 time s to 40 times, after perfusion of the arteries and veins with colored latex. RESULTS: The choroidal fissure is a natural cleft between the t halamus and the fornix, and it is identified by following the choroid plexus in the lateral ventricle. The choroid plexus in the body of the lateral ventricle originates from the tela choroidea of the roof of t he third ventricle and is apparently attached to the fornix by the tae nia fornicis and to the thalamus by the taenia choroidea. The taenia i s actually the ependyma that covers the internal wall of the ventricul ar cavity and the choroid plexus. CONCLUSION: An understanding of the choroidal fissure is fundamental for use of the transchoroidal approac h. Unlike transforaminal, subchoroidal, subforniceal, and interfornice al approaches to the third ventricle, which sacrifice some neural or v ascular structures, the transchoroidal approach follows a natural rout e, and certainly it is one of the options to be considered when entry into the third ventricle is required.