Abstract
To the neurosurgeon, the surgical treatment of third ventricular tumors, which are located in the deep midline of the cerebrum, an area considered inaccessible, present a major technical challenge, and the authors describe various possible approaches that can be used. One surgical method is the anterior trascallosal approach, based on the location, extension, and pathological characteristics of the tumor. This approach can be considered for patients with a third ventricular tumor that has no accompanying ventriculomegaly, with the site of the craniotomy determined on the basis of the angiographical localization of the parasagittal draining vein to the superior sagittal sinus. The technical problems involved with this type of callosotomy and with the separation of the interhemispheric fissure, so as to approach the corpus callosum, are discussed. Following a lateral ventricular entry, access to the chamber is then accomplished through the diencephalic roof to expose a third ventricular tumor by using the following approaches : 1) transforaminal, 2) interforniceal, 3) transforniceal, 4) subchoroidal, 5) transchoriodal, 6) transseptal, or 7) a combination of these approaches, and the authors discuss the possible physiological damage that may occur through using each of these approaches. With particular reference to the microsurgical anatomy, the topographical landmarks encountered when the third ventricular tumor in debulked and dissected also are discussed, as well as complications resulting from brain retraction, the division of the superficial and deep veins, the procedures of the callosotomy, and surgical injuries that may occur to the fornix, diencephalon, mesencephalon, and/or the basal forebrain structures.
