[Anterior transcallosal approach for the mass lesions in and around the third ventricle: with particular reference to the method of enlarging the foramen of Monro].

Enlargement of the foramen of Monro is an essential maneuver to obtain an appropriate surgical view when large, solid lesions in and around the third ventricle are to be removed via the anterior transcallosal approach (ATA). For this purpose, three methods, i.e., the subchoroidal, transchororidal, and transfornicial approaches have so far been reported. However, since the locations and the pathological natures of space occupying lesions in this region are widely variable, the indication as well as the feasibility of each approach has remained rather unclear. The present paper deals with our surgical experience with six patients (2 gliomas, 1 angioma, 1 AVM, 1 plexus papilloma, 1 basilar top aneurysm) operated on using the ATA in which variable methods of enlarging the foramen of Monro were employed. Aiming at complete removal or clipping of the lesion, the seemingly best among the above three approaches was determined preoperatively, considering the size, location, and pathological nature of the lesion. The shape of the choroid plexus of the roof of the IIIrd ventricle as revealed by MRI was also taken into account. The subchoroidal, transchoroidal, and the transfornicial approaches were employed in 3, 2, and 1 cases, respectively. Except for one glioma which ended up being removed extensively, all the tumors and AVM were totally removed and the aneurysm successfully clipped. From the above experience, the merits and demerits of each approach for different types of lesions are discussed in view of their suitability for achieving total removal.(ABSTRACT TRUNCATED AT 250 WORDS)