Hemorrhagic Colloid Cyst: Transcallosal Interforniceal Approach
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Hello, this is Aaron Cohen. This video review's resection of large hemorrhagic third ventricular colloid cyst, using the transcallosal interforniceal approach. This is a 42 year-old male, who presented with memory dysfunction and progressive headaches. And an MRI was noted to have a large hemorrhagic colloid cyst as demonstrated here on Cornell images. An important finding here is a very generous and spacious cavum septum pellucidum, which will affect our operative planning in terms of the operative corridor. The cyst has hypo-intensity on T2 weighted images, characteristic of hemorrhagic conversion of the large colloid cyst. The hemorrhagic colloid cyst of this size can be quite adherent to the surrounding structures, including the fornices. And this video will review technical nuances for a resection of this mass. As I discussed a moment ago, the spacious cavum septum pellucidum allowed us use the interforniceal approach, the transcallosal interforniceal approach to reach the mass. The use of the interforniceal approach in cases where the cavum is not available can be somewhat risky due to potential injury to the forniceal bodies and resultant memory dysfunction. In this case, we'll place the patient in a lateral position to be able to use gravity retraction on the non-dominant hemisphere. I use a lumbar drain to be able to achieve early decompression through CSF drainage and be able to carry on the inter-hemispheric dissection without significant intercranial tension. The cingula can be quite adherent and therefore, cerebral relaxation can be quite effective during micro dissection. This is an image from Dr. Roton's series, demonstrating the anatomy of the interforniceal approach. This is the right-sided sub-choroidal approach, which we'll not be using. And you can see compared to the interforniceal approach, the interforniceal approach is more direct toward the midline. The internal cerebral veins are located more on the sides of the operative corridor. And in this patient, the colloid cyst will be located here. So who'd expect to see both internal cerebral veins around the posterior aspect of our dissection through the interfoniceal anterior transcallosal interforniceal approach. With the patient in the latter position, the Dura is being open in the curvilinear fashion. A very small craniotomy was used just about two by three centimeters. A small parasagittal draining vein was disconnected. You can see how gravity has moved the brain away from midline. We used MRI-guided neuronavigation for this procedure. The superior sagittal sinus was unroofed, and as you can see, using dynamic retraction, the interhemispheric fissure was open. The cinguli or the cingulums can be quite adherent and patient microsurgical techniques is necessary. You can see the difference in color, the glistening white color of the callosum versus the more cortical color of the cingulum, which should not be confused or mistaken for each other. We'll go ahead and open the arachnoid membranes generously to be able to take advantage of gravity retraction. You can see the callosal marginal arteries that were separated from each other. This is a more de magnified view of the operative field. Using neuronavigation, a small callosotomy was completed. You can see the trajectory here and how the corpus callosum was very much attenuated. Just about a centimeter or a centimeter and a half of callosotomy is quite adequate to be able to reach the cavum in this case. You can see that interforniceal space, this is the left fornix. This is the cyst which is quite discolored. A small expansion of a callosotomy, more posteriorly was performed to be able to get a good exposure of the superior and posterior pole of the colloid cyst. We'll go ahead and continue. Now, coagulate the surface of the cyst. Neuronavigation continues to guide us in terms of where we are exactly. The cyst contents were evacuated using pituitary rongeurs. Here is again the operative trajectory. After the cyst was generously decompressed, we'll go ahead and find the internal cerebral veins. Should be located more posteriorly. You can see the left internal cerebral vein here. Using sharp dissection of the left internal cerebral vein and then the right internal cerebral vein, which you can see here, were mobilized away from the posterior capsule of the cyst. Sharp dissection is quite effective in protecting the veins. This is now the wall of the third ventricle. Again, the left internal cerebral vein, the right internal cerebral vein at the tip of my arrow. We'll go ahead and continue dissecting the capsule of the decompressed cyst from the left wall of the third ventricle. The internal cerebral veins are untethered from each other for me to be able to see the most posterior extended capsule of the tumor. This area can be challenging. You can see some choroid plexus. Also, these large hemorrhagic cysts are quite vascular in their capsule, as expected due to their increased risk of hemorrhage. And coagulation is necessary to exclude some of the feeders, As you can see here from the choroid plexus to the capsule of the tumor. As you will see a moment from now, I will get into some bleeding, mostly venous bleeding that I'll control with some patience and making sure only the vessel that is bleeding necessarily is controlled without an indiscriminate use of bipolar coagulation. If coagulation used indiscriminantly, it can lead to injury to the internal cerebral veins and potentially the wall of the third ventricle. So I'll continue to suction and just be able to see the exact point of bleeding, which is essentially from the choroid plexus, as expected to this lesion. And just about there, you find a feeder and bleeding was timely controlled. Here is another a feeder from the choroid plexus that was coagulated. And next cut we'll continue our sharp dissection along the walls of the third ventricle as much as possible. Here you can see the left wall of the third ventricle. Curved scissors in deep operative corridors can be quite effective for the operater to be able to see the exact tip of the instrument. Here's moving more to the midsection of the colloid cyst. Dissecting the roof of the, or the superior pole of the cyst and then mobilizing it from the bilateral forniceal bodies. You can see the fact that the cyst is so decompressed can help tremendously in it's dissection. I'll go ahead and remove more of the hemorrhage within the cyst thoroughly until only the wall of the cyst is apparent. We'll go ahead and dissect it now from the anterior aspect of the fornix on the left side. The fornices are very critical structures and they have to be very carefully protected. The use of sharp dissection as much as possible is preferred if necessary, some of the feeders should be first coagulated and then cut. Here you can see the adherence of the colloid cyst to the wall of the right lateral ventricle. Some of the small feeders are gonna be carefully coagulated and cut. But the wall of the ventricle should not be handled and rather the cyst wall should be manipulated. I sometimes use the bipolar as forceps and just pull the arachnoid layers toward the ventricle wall. We'll continue using angle instruments in the blind spot, which is more on the ipsilateral lateral ventricle. This area there was some evidence of gliosis and adherence to the forinceal body, which was dissected. We continue again further dissection along the inferior pole of the tumor here using those very fine vein that was adhering to the lateral wall of the capsule. You can see the pulling gentle avulsion of the adhering feathers of the wall to the tumor capsule, without significant coagulation to injure the surrounding structures. This is the last band that is connecting the cyst to the right side and next we'll proceed to dissect the cyst from the left side. Here is again the final dissection maneuvers and the cyst was delivered. You can see the final callosotomy, the walls of the third ventricle. Here you can see they bilateral internal cerebral veins they're both intact. The walls of the ventricles look well preserved. We went ahead and did a third ventriculostomy through the floor of the third ventricle. And bilateral septum pellucidum fenestration were also performed to assure no potential need for a ventriculperitoneal shunt after surgery. This patient did very well after surgery. Post-operative scan demonstrated removal of the mass. The patient's preoperative symptoms have since resolved. This is again using a one and a half centimeter ruler to demonstrate the extent of callosotomy, thank you.
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