Case Presentation

The case is of a ten year old girl admitted for intracranial hypertension with an MRI showing obstructive triventricular hydrocephalus due to a large mass located in the posterior half of the third ventricle occluding the sylvian aqueduct. Hydrocephalus was treated with endoscopic third ventriculostomy, and an attempt to biopsy the tumor failed due to hemorrhage from the lesion. It was therefore decided to approach the tumor directly for an attempt to maximum safe removal.

MRI shows a significant ventricular dilation. The mass in the posterior third ventricle probably arising from the left thalamus and a significant dilation of the both lateral ventricles. Sagittal images confirmed the central necrotic area of the tumor and the location in the posterior third ventricle. T2 drive sections are the best ones to clearly define the anatomical relationships of the tumor with the surrounding structures. And the coronal sections are important for the position of the cerebral veins. And on this basis, we can plan our options.

Through a standard callosotomy, the vision that is offered of the tumor is hidden in this case by the large massa intermedia that is anterior to the tumor. So any trajectory we choose through the callosotomy will be limited in the vision of the tumor because of the presence of the massa intermedia so probably transchoroidal approach will be better. But if we look carefully at this tumor and we realize that the superior part of the midbrain is separated by the tumor by a film of fluid and that the quadrigeminal plate is displaced posteriorly opening largely the aqueduct, certainly the approach from above is better.

And through the standard callosotomy, if we open largely the choroidal fissure, we can have very nice control of the whole tumor and of the whole third ventricle and be able to have better vision if compared to the transtentorial approach that at the end of the procedure would have less good vision of the region of the aqueduct. This is the area to cross interhemispheric fissure lateral ventricle, then the choroidal fissure to the cerebral veins.

Position of the patient is supine, head in a neutral position with 15 degrees flexion in 3-pin Mayfield head frame. Standard bicoronal incision and a standard bone flap for transcallosal approach extending three centimeters behind coronal and five, six centimeters anterior to coronal exposing the midline and controlling sagittal sinus. The dura is opened in a U or X fashion.

This is the 3D reconstruction of the tumor in relation with the brain. And in the following images, the 3D reconstruction of the trajectory with all the anatomical structures that have to be crossed and dissected during the approach to the tumor until the final target that is located at the inlet of the cerebral aqueduct. Again, the surgical trajectory in a profile view showing how deep is the final target and how long is the surgical trajectory for this kind of approach.