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Posterior Peri-Hippocampal Tumors: Supracerebellar Transtentorial Approach

December 16, 2015

Transcript

This procedure describes the techniques for Supracerebellar Transtentorial Approach for a section of Posterior Peri-Hippocampal Tumors. This is the case of a 62 year old female who presented with a seizure and was diagnosed with a single brain metastasis. On the MRI there is a well-defined lesion along the posterior aspect of the peri hippocampus. The approaches to this lesion are quite varied. A number of different approaches have been described by the colleagues, the subtemporal approach, which is most likely the most commonly used approach requires a significant amount of temporal lobe retraction to reach the superior pole of the tumor. This amount of retraction places, the speech areas along the middle temporal gyrus at risk, and also places the vein of the bay at risk of avulsion injury. Because of the attended risks of it subtemporal approach. I have used the supracerebellar transtentorial approach to reach the poster aspect of the peri hippocampus. I find that this approach, the most flexible and least risky in terms of placing the supratentorial structures at risk. So as you can see the vector or trajectory of the approach or the operative corridor is through this supracerebellar route while cutting the tentorium in T-shape fashion to reach the tumor. Obviously this working distance is quite long and quite narrow. You can also appreciate the location of the mass along the post per hippocampus. That supracerebellar transtentorial approach can reach essentially any lesion posterior to the uncus. Anything interior to that is beyond the reach of this approach. In addition, this approach is quite inflexible. If the lesion is not a properly selected for resection. In other words, the lesion cannot be more lateral or more interior in terms of each location. Intraoperative neuro navigation is used. A lumbar drain is placed at the beginning of the surgery. The head is fixing this called clamp and the patient is positioned in the lateral position with the head turned just very slightly toward the floor. Neuro navigation is used to mark the transverse sinus approximately five or six centimeters incision is used with two third of incision below the transverse sinus and one-third of incision above the transverse sinus to provide adequate exposure of the supracerebellar corridor. The shoulder is moved out of the way as much as possible by taping it. If needed, you can see the use of the lumbar drain for early cerebellar decompression. The exposure is revealed here. You can see that a barrel was placed over the medial aspect of the transverse sinus, the bone over the transverse sinus is completely on roofed. Small craniotomy is completed. The foramen magnum is not opened and the bony removal especially focused just below the transverse sinus to dural sutures are used to retract the dura. Additional retention sutures can be placed along the poster aspect of the tentorium to mobilize the sinus out of the way more effectively. Neuro navigation is used to identify the location for the T incision within the tentorium. Again, there is a relatively straight incision, just parallel to the transverse sinus and one vertical to expose the posterior aspect of the base of temporal lobe. The lumbar drain provides adequate decompression and mobilization of the cerebellum away from the tentorium. You can see these two additional retention sutures. Neuro navigation is used to identify the poster pole of the tumor and accurately and precisely define the location of their tentorial cuts. Carlin blade is used for the initial incision within the tentorium to cut the tentorium toward the surgeon. Subsequently a pair of scissors are used to cut the tentorium to the incisura here's the T incision and its horizontal limb. You can see the use of the ankle hook to hold a 10 term away from the occipital lobe. The incision is extended medially. Two sutures are used under flaps of the tentorium to mobilize the flaps inferiorly. The limb of the T incision is extended more anteriorly. One has to be careful to avoid injury to the trochlear nerve along the edge of the incisura. The extent of this tentorial incision again is guided based on neuro navigation. I use intra-operative florists in fluorescence for guiding the resection of this tumor. You can see that I'm essentially anterior to the tumor at this juncture. So adequate exposure has been secured. Small court economy is completed along the base of the tumor and the tumor is first debulked using a pituitary rongeur. And in micro surgically resected from the surrounding. White matter tracts. You see the characteristic of the tumor, which is relatively robbery and grayish. You can see that I'm essentially in the middle of the tumor fluorescence identifies additional residual tumor, more medially, that will be also removed. Any of their vessels associated with a posterior cerebral artery should be protected in this area. The tumor can be frequently at here into some of the branches of the PCA. Here is their poster aspect of the temporal horn and some of the vessels within the ventricle that have to be carefully protected to avoid any visual decline. Again, the PCA branches that are coursing around this area should be protected to avoid any risk to the vision as well. You can see the final operative trajectory through that supracerebellar exposing generously the area of the occipital lobe and the basal temporal region. No retraction of the supra tectum contents was necessary. The cerebellum is quite healthy, fixed retractors were avoided and can often complicate that deep reach of the exposure due to their very inflexible vector of retraction. The tentorium is not sutured together and is left over the cerebellum. This is the postoperative MRI demonstrating complete resection of the tumor without any untoward side effect. Thank you.

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