Tentorial Opening

At this stage, tentorial opening is a key part of the procedure. We proceed coagulating extensively the tentorium with the bipolar coagulation. As you can see, we are using a bipolar with a relatively high power in order to coagulate all the venous lakes that are embedded in the tentorium remaining, of course, far away from the straight sinus.

And after an extensive coagulation, we proceed fast with the thulium laser that is a very good tool to vaporize completely the tentorium. And that is very fast in opening it. Sometimes some further coagulation is necessary, but normally the thulium laser can allow a very quick, very clean, and very tailored opening of the tentorium in order to expand as much as possible our field of view on the region of the quadrigeminal cistern.

The large opening of the tentorium is a very, very important point in order to obtain the best possible vision on the contralateral side. Here, we separate the tentorium from the veins that are lying below. And we prepare the upper part of the tentorium for a further vaporization with the thulium laser. At this point, we can clearly see the capsule of the tumor that is hidden below the tentorium itself. And we can continue our work of dissection and separation of the vein from the capsule of the tumor.

The opening of the tentorium, as you see, gave us access to the higher part of the tumor capsule. And now, it is certainly more clear, the position of the right basal vein of Rosenthal and on the right complex of the internal cerebral occipital veins if compared with the capsule of the tumor. Then we continue our enlargement of the arachnoid dissection and opening. And this offers to us access to the dissection plan above the tumor.

We continue the dissection of the veins from the tumor. We recognize here the left internal occipital vein that is fortunately quite easy to dissect from the tumor capsule. We can identify a dissection plan that is very clear in this phase between the deep vein complex and the capsule of the tumor. And we can follow the dissection plan respecting the veins. At this time, coagulation and shrinking of the capsule is indicated in order to favor access to the inner part of the tumor.

We can see that the shrinking of the capsule makes easier also the dissection of the veins that are adherent to the capsule itself. And we are preparing as well as possible the capsule for a sharp opening and for access to the content that will allow a progressive debulking of the internal part of the tumor. We recognize here the left basal vein of Rosenthal. And we can continue our dissection after mild shrinking of the capsule.

We recognize always very well the plan of dissection between the tumor capsule and the deep vein complex. This work can be very, very long and must be done with extreme care in order to avoid to injure the veins that are only in the plans before our working plan. We can coagulate the small vessels that are very tiny. And that facilitates the recognition of the dissection plan.

But you see that the vision of the plan of dissection between the tumor and the deep vein complex is extremely good even using this approach. And we can have a good vision of the upper part of the tumor and of the highest part of the dissection plan with a good orientation of the microscope and with a very comfortable working angle, both for our microscope and for our instrumentation.

This work of dissection as you see is very slow. It must proceed millimeter by millimeter. And you see that the small veins that are lying above the plan of the tumor capsule can be dissected quite easily. All of this space that is progressively gained with the dissection is vital in order to improve our anatomical recognition of the tumor volume and in the respect of the vital structures that are hidden below the tumor.

And we are progressive in the dissection. You can see that fortunately the tumor is very compact. And its consistency is very favorable to our dissection, because it is completely independent from the structures of the parenchyma that surrounds it. And here, you see that the dissection is progressing slowly to go to the lower pole of the tumor. Here, we found more veins that nevertheless can be progressively and slowly dissected with a very, very careful dissection with the suction cannula that you can see is limited to the lowest power of aspiration, of course, in order to avoid the risk of injuring a vein with an inadvertent suction.

We can see the very small vessels that are on the interface between the tumor and the tectal plate in the inferior part of the tumor level. We study this distribution of vessels to understand, which are the vessels that are pertinent to the capsule of the tumor and which are the vessels that are instead part of the tectal plate venous system? So we can decide which one of these can be sacrificed. Here, we try to dissect one of these veins.

Clearly, we’re trying to understand if this vein can be sacrificed or if this vein must be preserved. In the lower part, we clearly recognize a network of veins and small arteries that need to be respected in order to preserve the venous and arterial network of the ductal plate. We position a cottonoid in the dissection plane that is most clearly and anatomically evident in this part of the dissection. Sometimes it can be difficult to dissect. And then we have to use the sharper dissection in order to separate the small vessels from the tumor capsule.

A mild traction with the suction cannula can help in understanding, what is the correct dissection plan. Here, it is very evident the dissection plan between the brain and the tumor capsule. And finally, we can progress more accurately at this level with the dissection, slowly and progressively pushing our cottonoid in the dissection plan that is identified in this way. We continue very slowly this dissection with a very gentle traction, both with the suction cannula and with the bipolar forceps.

Then we go back on the other side after this initial dissection on the lower part. And we identify some small vessels that can be coagulated on the surface of the tumor capsule. These are large tumor vessels that can certainly be coagulated , because they are inside the outer layer of the tumor capsule. And this shrinking of the capsule helps very much in understanding and facilitating the dissection from the contralateral venous system.

Here, we will take some time to dissect better the superior vermian vein. And finally, we approach the tumor with a strong scissor that is necessary to take a sample biopsy. A strong scissor is necessary because of the texture of the tumor that is quite typical of teratomas. And that requires a relatively strong instrument to perform a large sample of the lesion. You can see that the content is quite typical– white, avascular, very firm. And quite typical of teratomas.

And here, we continue our section. You see how much time it is necessary to cut this fragment of tumor, including the capsule and some part of the tumor content. You see that the lesion is relatively avascular. Vessels are mainly located on the surface. And for this reason, coagulation of the capsule from outside is extremely useful in decreasing the size, decreasing the vascularization of the lesion and facilitating further dissection of the lesion.

You see that here we take all the time to carefully coagulate the outside of the tumor capsule. This certainly helps not only the future steps of the opening of the capsule and the internal debulking, but also in depth helps significantly in the work of the dissection of the tumor. You see that the plan of dissection is relatively easy to find in teratomas. But the coagulation, progressive shrinking of the capsule helps significantly in keeping well delimited the plan of dissection and identifying the depth of the lesion.