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Recurrent Insular Pilocytic Astrocytoma

March 02, 2015


Let's discuss resection of a reccurent insular pilocytic astrocytoma. This is a 16 year old male who underwent surveillance imaging and was noted to have recurrence of his cystic pilocytic astrocytoma in the left insular. You can see the location of the nodule relatively lateral and also just underneath the posterior surface of the insular. There is some mass effect associated with the cyst. The surgeon underwent re-opening of his left front temporal craniotomy. The dura is obviously very adherent to the surface of the pia because of the history of surgery. I, therefore, only cut the dura over the area of the Sylvian fissure to minimize any injury to the surface of the brain. Next, I carefully inspect the inner surface of the dura to make sure there are no veins significantly adherent to the dura. Sharp dissection is used. Obviously, there will be some veins that are very adherent and the small ones may have to be coagulated. Here's the previous area of the corticotomy. I attempt to use the previous operative corridor and avoid creating new operative corridors, especially in this area which is quite functional. I inspected the area for any other important veins including vein of Labbé. And the dura was also opened more posteriorly as guided by inter-operative image guidance to make sure that the nodule is adequately exposed. Here's the route of the vein of Labbé. This area is not very adherent and this is the target area. I go ahead and enter the previous operative corridor and corticotomy. The nodule should be situated just underneath this area, reaching just the surface of the nodule. This cyst should be also easily drainable. I used retention sutures to mobilize the dura out of my working zone. Additional surface of the brain was exposed just in case an extended corticotomy beyond the previous borders would be necessary. Here's the surface of the cyst. Thin membrane over the cyst. I'll go in and open the cyst and inspect its walls to find the nodule. Here's nodule just underneath the corticotomy. I'll go ahead and undermine the edges of the corticotomy to be able to remove the nodule. Here's the drainage of the cyst. I can see the walls of the cyst, the gliotic walls. Obviously, I'm not going to remove the entire wall of the cyst, but just only the nodule. You can see the part of the nodule that is somewhat of a different color than the surrounding peritumoral, gliotic tissue. And using the bipolar forceps to disconnect the nodule from the surrounding, relatively normal, brain. Neuro-navigation assists with localization and the borders of the nodule. You can support the nodule that was left behind more inferiorly. This part is being removed until relatively normal appearing brain is found. You can see another small nodule potentially within the cavity. This will be removed as well. Here's the larger nodule that will be removed momentarily. There is a MC branch within this portion of the nodule that obviously has to be protected. I may have to leave a small piece of the tumor around the vessel to protect the viability of the vessel. One has to be very cognizant of these vessels. As you can see, this is a relatively robust vessel that should not be sacrificed. One has to always look for these during the dissection, especially in this area. I did not find any other nodule and you can see the wall of the cyst. No significant discoloration related to the tumor is apparent. The vessel is gently mobilized using dynamic retraction. You can see the other walls of the cyst that appear tumor free. And the post-operative MRI, in this case, demonstrated adequate removal of the nodule, drainage of the cyst and no evidence of untoward effects. Thank you.

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