Stereotactic Localization of the Monro Foramen and the Safest Stereotactic Interforniceal Approach to the Third Ventricle: A Neuroanatomical Study

Abstract

The present study shows how neurosurgeons can localize and use crucial anatomical landmarks, namely the AC and foramen of Monro, to approach the third ventricle safely via a stereotactic interforniceal technique. This can be achieved during preoperative planning with simple identification of stereotactic points A, B, and M on preoperative median sagittal magnetic resonance images.

Stereotactic anatomy of the third ventricle

“…Previously we used 26 adult cadaveric brains and 200 adult brain MRIs describing the third ventricle floor and related structures and concluded that, in older subjects and when the basilar artery caliber was larger, its apex was closer to the floor of the third ventricle [ 5 ]. Mavridis and Anagnostopoulou described the stereotactic localization of the anterior-inferior border of the IVF and the midpoint between it and the anterior commissure, using 44 cadaveric hemispheres to define a safer approach to the third ventricle [ 15 ]. Using the posterosuperior border of the anterior commissure as the stereotactic reference point, these authors found that the mean stereotactic Y coordinate of the IVF anterior-inferior border was -0.61 ± 1.58 mm and the mean stereotactic Z coordinate for the same point was 2.41 ± 2.93 mm [ 15 , 20 ].…”

“…Mavridis and Anagnostopoulou described the stereotactic localization of the anterior-inferior border of the IVF and the midpoint between it and the anterior commissure, using 44 cadaveric hemispheres to define a safer approach to the third ventricle [ 15 ]. Using the posterosuperior border of the anterior commissure as the stereotactic reference point, these authors found that the mean stereotactic Y coordinate of the IVF anterior-inferior border was -0.61 ± 1.58 mm and the mean stereotactic Z coordinate for the same point was 2.41 ± 2.93 mm [ 15 , 20 ]. Comparing these measurements with the present results (mean ± SD: Y = − 1.92 ± 0.779 mm; Z = 3.94 ± 1.175 mm), it was found that the anterior border of the IVF seems to be placed slightly more posteriorly and superiorly, but the difference does not appear to be significantly different.…”

“…In the cadaveric brains, analysis regarding the differences between sides and sexes were not conducted due to an insufficient number of specimens and their anonymity. However, Mavridis and Anagnostopoulou found that the anterior border of the left IVF was located more posteriorly than the right one, even though there was no statistical significance [ 15 ].…”

“…The size of the IVF, the location of the infundibular recess and third ventricle floor, the termination of the basilar artery and the emergence of the oculomotor nerve are critical to obtain an optimized ETV trajectory [ 1 ]. Therefore, neuroanatomical studies to obtain normative morphometric data are one of the basic means to minimize complication rates [ 5 , 14 , 15 ].…”