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Lateral Ventricular Tumor (Neurocytoma): The Interhemispheric Transcallosal Approach

December 17, 2015

Transcript

Let's talk about resection of lateral ventricular tumors and more specifically a neurocytoma. This video also describes the details of the interhemispheric transcallosal approach for reaching the deep lateral ventricle. This is a 48 year-old female who presented with fatigue, memory difficulty and headaches. And on MRI was noted to have a heterogeneously enhancing acystic mass centered over the lateral ventricle and more toward the left side. And the mass is also centered over the ear of this septum pellucidum. You can see that this tumor is along the mid to posterior aspect of the corpus callosum. Also there is close association of the inferior pole of the mass to the veins along the inferior aspect of the lateral ventricle and roof of the third ventricle. Since the tumor is more toward the left side, a left sided interhemispheric transcallosal approach was deemed more appropriate. Lumbar drain was placed to allow decompression and a smooth dissection through the interhemispheric corridor. The patient may be placed in a lateral or supine position. In this case, the patient is in a semi-lateral or semi-supine position. The contralateral shoulder is propped up using a large gel pad. The sagittal suture is parallel to the surface of the floor. This maneuver allows retraction through the gravity on the hemisphere and obviates the need for fixed retractors. The skullclamp is pretty standard in its position. A neuronavigation using MRI is indicated and a lumbar drain was used. Here is completion of the craniotomy. Two burr holes were placed over the super sagittal sinus. A left posterior frontal craniotomy was completed. The coronal suture is approximately over this area therefore the extent of the craniotomy just slightly posterior to the coronal suture to allow a more posterior trajectory toward the tumor along the posterior aspect of the lateral ventricle. On of the superior sagittal sinus is necessary to allow its mobilization during retraction of the dura. This maneuver moves the sinus out of the working zone of the surgeon during the interhemispheric dissection. Approximately 40cc of CSF is slowly drained to allow decompression of the brain. The dura is open in a curvilinear fashion based over this sagittal sinus. As you can see here, one of the lagoons or lakes of the super sagittal sinus in the parasagittal area was inadvertently entered. Bipolar coagulation is avoided and the dural tear is closed using a suture primarily. Here's the location of our entry along the interhemispheric corridor. Based on this craniotomy, you can see that the craniotomy is posterior and is somewhat to the middle of the tumor as desired. Next the adhesions along the interhemispheric space are dissected, there's a piece of bone in the dura that will be removed. Two sutures are placed over the superior aspect of the falx and these retention sutures move the sinus out of the working zone of the surgeon. Here's the final product without any use of fixed retractors. You can see gravity retraction and its effect. You can see the location of our dissection. Interhemispheric sub-arachnoids dissection is started. The vessels are used as a roadmap to dissect the section between the two cinguli. Here you can see the glistening yellow color of the corpus callosum compared to the cortical color of the cinguli or cingulium. I continued dissection between the two pericallosal arteries. Here is the two pericallosal arteries. Here's the corpus callosum. Aggressive coagulation is avoided. Ample amount of irrigation is used that can be cleared through gravity. Generous dissection on tethers, the two hemispheres and allows ample amount of space for the later stages of the operation. You can see the dissection of the arachnoid bands, the use of short dissection as much as possible between the two arteries avoiding any peel injury to the cingulate gyrus especially if it's the laterally which is a dominant one. Two cotton balls are used to open the interhemispheric corridor and keep it open without the use of fixed retractors. The brain is covered with a piece of to avoid injury from the intense heat of the microscope. Here's an unfortunate situation that occurred due to some bland dissection. One of the perforator arteries to the ipsilateral preauricular was injured. You can see the hole within the preauricular artery. In this circumstance use of 8-0 or 9-0 sutures to close the defect is often not very fruitful based on my experience. I use a piece of cotton soaked in thrombin and hold gentle pressure over the area of the bleeding. This maneuver seems to work every time. The use a suture often creates additional bleeding through the holes of the suture and the working space can be quite limited for placement of the suture at this juncture. You can see this small piece of cotton was effective. The artery remains very healthy. It's manipulation may lead to some vasospasm that will be relieved using papaverine soaked piece of cotton over the artery. Here's the artery more spasm because of its significant manipulation. A piece of cotton soaked in papaverine is used to bathe the artery and relieve the spasm. Micro-Doppler ultrasonography confirms adequate flow within the artery. I continue with it small callosotomy over the center of the tumor. The initial callosotomy is very limited until the tumor is exposed. And based on the initial findings within the ventricle, the callosotomy is extended anteriorly or posteriorly. You can see the cystic fluid that is discolored from the tumor within the ipsilateral ventricle. This is the location of our callosotomy over the center of the tumor. Now the callosotomy is extended more posteriorly to be able to reach the most posterior pole of the mass. Here's the tumor that's being exposed. Here's the tumor injured. And we continue with tumor debulking Pituitary injures are used to decompress and debulk as much of the tumor as possible until the walls of the ventricle are identified. Here is again our location and the working zone. As the tumor is debulked, the ventricles are exposed and anatomical orientation is more complete. Again, this tumor affects the septum pellucidum. It's a neurocytoma and both ventricles have to be identified before the tumor is transected and its spaced. So here is entry most likely into the right lateral ventricle. Here's the tumor affecting the septum pellucidum. Here are the inferior aspect of the ventricle and the choroid plexus on the right side. Now it's time to find a ventricle on the left side. Here's additional space and CSF leading us to the ipsilateral ventricle. Here's more tumor. Most likely now we are in the ipsilateral hemisphere, and this is the wall of the ventricle. Now we have both ventricles identified. I can be more aggressive for tumor removal, getting to the base of the tumor at the roof of the third ventricle and rolling the tumor more posteriorly. So here you can see again the ventricular space is more anteriorly. That's the contralateral ventricle. Let's go ahead and find the ipsilateral ventricle. Here's the septum pellucidum that's being dissected and transected so additional space is secured. Here's the ipsilateral ventricle that is now much more evident. Here's the unaffected septum pellucidum. So now the tumor is transected at its base and rolled posteriorly. The unaffected inferior aspect of the septum pellucidum is evident. These anatomical landmarks and steps and their orders are quite critical to avoid any inadvertent injury to the surrounding walls of the ventricle. Here's more devascularization of the tumor more posteriorly. Here a dissection of the tumor from the septum pellucidum along the contralateral ventricle. Here's some residual tumor on the ipsilateral ventricle. Contralateral ventricle looks clean. Portion of the tumor was removed. Here now you can see that tumor is affecting the ipsilateral ventricle and some of the veins along the ventricular wall. Here is additional tumor affecting the posterior septum pellucidum. Here is the tumor reaching the walls of the ipsilateral ventricle. You can see the tumor normal septum pellucidum interface. Here is the more posterior aspect of our dissection cavity. The normal medial ventricular wall and part of the splenium can be evident. Here's the tumor being lifted away and delivered into our resection cavity from a posterior to anterior direction. The most difficult part and the blind spot is under the corpus callosum within the ipsilateral ventricle. That's where the surgeon often leaves tumor behind. The internal cerebral veins are located along the posterior superior aspect of the third ventricle just below the tumor posteriorly and have to be carefully preserved. Here's additional tumor within the posterior lateral ventricle. I'm coming back to that blind spot I talked about just underneath the ipsilateral corpus callosum. Here's the internal cerebral veins we talked about along the posterior aspect of the floor of the lateral ventricle. Here's the tumor that is being delivered into the resection cavity. However the tumor seems to be very adherent to the lateral ventricle wall. Here's some of the veins that are engulfed by the tumor. Here's another vein. Small piece of the tumor had to be left behind to protect these veins. Here is the internal cerebral veins posteriorly. Here's septum pellucidum that is no longer affected by the tumor. Coagulation of the small remnants of the tumor was performed over the veins. Here is a final view of the resection cavity. Further inspection was performed using an endoscope. You can see the tumor is adherent to the veins on the lateral wall of the lateral ventricle. Further inspection of the space underneath the contralateral corpus callosum was also conducted to ensure complete resection of a tumor within the blind spots of the surgeon. Here's another funnel view of the operative space and postoperative MRI demonstrated. Radical subtotal resection of the tumor with small amount of residual tumor adherent to the large draining vein onto the lateral wall of the ventricle. And this patient recovered from surgery without any complications, thank you.

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