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Large Third Ventricular Tumors: Transcallosal Transforaminal Transvenous Route

December 17, 2015

The photos of this patient are included in this video by means of the written consent from the patient.

Transcript

This video reviews the tenants for exposure of large third ventricle tumors through the transcallosal transvenous transchoroidal route. I essentially use the transchoroidal approach to expose the foramen of Monro and then sacrifice the septal vein and then sacrifice the septal vein to expand the foramen through a minimal transchoroidal route. This minimal transchoroidal route, by transecting the septal vein, minimizes the injury to the fornix and thalamus, but at the same time provides very sufficient exposure through the third ventricle to remove large tumors. This is a 32 year old female who presented with six months history of progressive headaches and nausea. She unfortunately underwent unsuccessful resection of her third ventricular tumor through a transcortic approach, as you can see here. The tumor was biopsied. However, the exposure by the initial index surgeon was not to be insufficient for removal of the tumor. And therefore the tumor was not removed. I approached this tumor through the interhemispheric trans closer route. This case signifies the importance of the interhemispheric trans closer route in removing a large third ventricular tumors, and also emphasizes the shortcomings of the transcortical route for removing third ventricular masses. The transcortical route is quite limited in its anterior posterior reach. However, the transcallosal route provides additional space for removal of the larger tumors because of the expanded anterior posterior angles of work. You can see that this tumor is somewhat cystic, primarily located within the third ventricle and is most likely affecting the flow of the third ventricle and the pituitary stalk. Therefore, if the tumor is very adherent along the floor, small piece of tumor should be left behind to avoid any injury to the area. Another important finding on preoperative imaging is the location of the floor of the third ventricle hypothalamus which is intact, not affected by the tumor and also the optic chiasm, which is very much covering the inferior pole of the tumor. Therefore, a transnasal approach is not ideal for removal of this tumor because you will place both the floor of the third ventricle and the chiasm at risk. Let's review the nuances for the transcallosal, transforaminal, transvenous, transchoroidal approach for resection of this mass. The patient was placed in a supine position. A linear incision, just anterior to the coronal suture was used for the interhemispheric route. This is the location of the sagittal suture and the superior sagittal sinus. Previously, a similar longer incision was used. Here's the initial exposure. You can see that the roof of the superior sagittal sinus was removed. The craniotomy is relatively small and extended toward the left side. Two sutures were placed along the superior aspect of the fox to mobilize the sinus out of my working zone. I use a piece of rubber dam or a piece of cloth, cut to a shape a cottonoid in order to slide around the frontal lobe and avoid any injury from the rough surfaces of the cottonoid on the cortex of the medial hemisphere. The brain that is not manipulated is covered with a piece of Telfa to avoid any cortical injury from the intense heat of the microscope. A lumbar drain was also used to achieve early decompression of the hemisphere. You can see the location of the trans closure route in relation to the intraoperative navigation MRI. Small callosotomy was completed to the length of approximately a centimeter and a half. Here, you can see the operative trajectory under less magnification. Fix retractors were avoided and a very small callosotomy was necessary to reach this lesion. Again, their retention sutures mobilized the superior sagittal sinus out of my inter-hemispheric corridor. Here's the location of the foramen. It's very small. Some scarring is present from initial surgery. Here's the thalamostriate vein. Here's the septal vein. Here's the tumor. Here's the choroid plexus or the choroidal fissure. The plexus is coagulated and mobilized in expectation of a very minimal anterior transchoroidal incision. I extended the transchoroidal route until the septal vein is encountered. At this location the septal vein joins the thalamostriate vein. You can see the septal vein joining the thalamostriate vein. This span is coagulated and cut. Here's the thalamostriate vein. Here's the septal vein posteriorly. Here's the coagulation and transection of the septal vein. Now the foramen is expanded. The choroid plexus is further coagulated and cut. The fornix is gently mobilized medially using dynamic retraction of the dissector. Here's the apostle of the the third ventricle through the expansion of foramen of Monro. Here's the internal cerebral vein on the right, and we'll see the internal cerebral vein on the left in a moment. Here's the tumor. Here's contralateral internal cerebral vein, the posterior wall of the third ventricle and the tumor. A very generous exposure is attained. The tumor is first debulked aggressively before its capsule is dissected from the surrounding vital third ventricular walls. The magnified view of the opera field was provided for your orientation. You can see a very minimal interior transchoroidal approach was necessary. The tumor is further debulked as much as possible. And then the capsule is mobilized away from the anterior third ventriclular wall. The steps of debulking and dissection of the wall and its delivery into the resection cavity are repeated. An ultrasonic aspirator is used to remove this fibrous tumor without placing the third ventricle walls under a significant traction because of pulling on the tumor to remove it. The tumor has a very heterogeneous character. Its final pathology was consistent with a chordoid glioma, which is quite rare. Primarily found in the third ventricle. It's important to avoid inadvertent violation of the capsule with the use of the ultrasonic aspirator. As this may lead to injury to the third ventricular walls. Portion of the tumor are quite firm. The blind spot of the operator is close to their contralateral or their left third ventricular wall. So the tumor has to be really aggressively debulked in this area and then mobilize into the resection cavity. And the walls of the third ventricle has to be protected as much as possible. Here's some of the attachments of the tumor that are being released. I continue dissection very close to the capsule of the tumor. Thorough debulking is one of the key components of removing tumors through a very small working spaces such as the foramen. Here, you can see now the tumor along the poster wall of the third ventricle, the tumor slightly adherent to the left wall. This adherence is more noticeable along the hypothalamus and flow to the third ventricle as expected based on preoperative images. as expected based on preoperative images. I continue to work around the tumor in a circumferential manner, and unnecessarily in a deeper areas or in one area more deeply than the other. Here is further mobilization of the tumor along the left ventricular wall. You can see the tumor is quite adherent to the floor of third ventricle. Therefore, a piece of tumor will be left behind there. I use the ultrasonic aspirate to thin out as much as this residual piece of the tumor that'll be left behind at the floor. So only a very thin sheet of tumor is left over the hypothalamus. Here again, that small piece of the tumor that is quite adherent, flow to the third ventricle. This last piece of the tumor is again, fend out as much as possible. Here's the final operative corridor through the expanded foramen. Small piece of the tumor that was left behind is noted. This small piece is further coagulated to minimize the risk of recurrence. Here's navigation demonstrating the location of the section, just at the bottom of the tumor. An external ventricular drain catheter was placed after immaculate hemostasis. Post operative MRI demonstrated radical near total resection of the tumor radical near total resection of the tumor with a small piece of the tumor left over the stock and the floor of the third ventricle. This patient had a brief period of diabetes insipidus after surgery, but since then has made an excellent recovery and has returned to work without any untoward side effect. This video primarily describes the important learning points as related to expansion of their foramen for reaching large third ventricular tumors, and also emphasizes the importance of dynamic retraction in removal of deep seated tumors to protect the thalamus, internal cerebral veins, as well as the fornacis. This is also a picture of the patient at her three months evaluation. Thank you.

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