Atrial/Splenial AVM: Transfalcine Route
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The posterior contralateral interhemispheric transfalcine approaches, specially well-suited for removal of periatrial or peritrigonal or splenium arteriovenous malformations. This is a 32 year old female who presented with headaches and was diagnosed with this unruptured periatrial located along the medial wall of the atrium and partially splenium arteriovenous malformation. As expected the feeding vessels are primarily from the anterior cerebral artery and its distal branches, as well as some of the PCA distal branches. The draining vein obviously joins the Galen into the straight sinus. The ipsilateral interhemispheric approach that is commonly used for removal of the smell formation, can be somewhat challenging. In my view, since the lateral pole of the tumor would require significant amount of cortical retraction and potentially transgression for its exposure and control. Any bleeding from this portion on the nidus, can be difficult to control, since it's within the blind spot of the surgeon. Therefore, the contralateral interhemispheric approach provides a more direct line of view toward the lateral projection of the malformation. And importantly provides early control over the feeding vessels at a pedicle or the lower portion of the malformation. Facing the choroid plexus and also controls the plexal feeders to the malformation. Let's go ahead and review the events of this surgery as they unfolded. You can see the patient is placed in the latter position with the unaffected hemisphere down. So I can exploit gravity retraction. Superior sagittal sinuses unroofed, a lumbar drainage installed for early brain decompression. The head is turned 45 degrees toward the floor. Here's another view for head positioning, a placement of the skull clamp. Here's the craniotomy, a relatively small, you can see the superior sagittal sinus is unroofed. We'll go in and open the door in a curvilinear fashion. Lumbar drainage is used to decompress the brain. You can see some of the veins transversely, operative view and the interhemispheric trajectory, the arachnoid bands are carefully untethered, so that the dominant veins can be protected, as you can see here. You can see the brain is falling away because of gravity retraction. The transfalcine approaches utilized as described in the present chapter. The T-shaped transfalcine incisions are created. The first one of which is parallel to the superior sagittal sinus, the splenium somewhat posterior. And the incision within the falx has to extend posteriorly. One of the important pitfalls in the falx seeing incisions is protection of the straight sinus. As the incision extends posteriorly, the T-shaped incision is extended inferiorly and the inferior sagittal sinus is transected again. One has to be very careful using neuro navigation and anatomical landmarks to protect the straight sinus and its associated venous lakes within the junction of the tentorium and falx. You can see, here the junction of the falx in the tentorium. Here's the final cut within the inferior sagittal sinus until the corpus callosum and the splenium are unveiled. Here you can see the straight sinus draining posteriorly incision ended up to be just next to the interior of the sinus. Here, you can see the transfer sinus associated with a lake. You can see how I'm cutting the falx just around the straight sinus and not perpendicular to it. So that I can extend my operative view more posteriorly. Here's dissection along this straight sinus contralaterally. This is really a beautiful exposure for this location. Here, you can see, the veins draining the arteriovenous malformation. The arachnoid bands are generously opened. So that the identity of the arterialized vein here is evident. Here, you can see it in magnified view of our exposure. This is the arterialized vein, leaving the AVM. Is the splenium. Next, the arterials manus pursued using navigation until the nidus is exposed. Here, you can see the arterialized vein joining the vein of Galen. Medial occipital lobe is located here. Here's a small incision within the precuneus so that the nidus of the malformation can be circumferentially dissected. I continue to remain within the who the Arctic brain porting the malformation here again, continuation of RD section to expose the nidus. You can see that the operative distance is quite long dynamic retraction, especially beneficial, fixed retractors should be avoided. As these blades can actually interfere with the extent of exposure. I continue to follow the vein. The malformation is most likely more interior. The vein is being untethered. Here's part of the splenium that is being dissected from the vein. Some of the white matter feeders to the nidus are also identified and sacrificed. Here's the dissection below the nidus across the splenium. Some of the feeding vessels are co-coagulated and cut. Here is a more distal part of the vein. The vein appears to be slightly darker at this step of the operation. Here's some of the feeding vessels originating more inferiorly facing the AVM. This portion of the nidus that is removed, here, is there atrium of the lateral ventricle that is being entered. Here's a vein on the wall that was sacrificed. I did not see any other abnormality to make me believe additional pieces of nidus could have been left behind. Carefully inspection reveals no other residual AV shunting or malformation. However, I was suspicious that is potentially some residual malformation anteriorly that has gone unnoticed. I was just not very impressed with the size of the nidus that I removed. I continue to co-coagulate some of it surrounding periatrial surfaces. All the veins appeared dark. Here's the fun or a section cavity and the entry into the triagonal or the atrium. I requested an intraoperative angiogram next to evaluate any potential of residual malformation. The intraoperative angiogram confirmed my suspicion that there is some evidence of malformation anterior to my resection cavity. Therefore I explored this area more effectively. I continued along the anterior aspect of the previous resection cavity found some of these feeding vessels. I do believe that this AV was more diffused than anticipated based on preoperative angiogram. However, I remained somewhat conservative for my planes of resection, but unfortunately faced some intraoperative bleeding most likely related to these diffuse white matter feeders involving this splenium and the walls of the ventricle. Persistence in controlling bleeding is specially important. You can see that the bleeding is somewhat directed, more anteriorly. I had to extend my cordectomy in the same direction to be able to clearly visualize the source of bleeding. You can see these are the white matter feeders at the medial wall of the ventricle. There's also a plexal feeder here that was controlled and cut. These white matter feeders originating from the wall of the ventricle and quadplaxes can be quite challenging to control. The choroid plexas should not be aggressively, co-coagulated as some of it's emphasized feeding vessels to the walls of the ventricle or important for nourishing the optic radiations. Here's again, the lateral wall of the ventricle part of the core plexus in this case had to be co-agglulated because it feeders ended up in the nidus no obvious AV shunting is apparent. I continue to explore their medial wall of the ventricle to assure myself that no other predominant white matter of feeder could be responsible for additional AV shunting. Here's the residual nidus that is being mobilized, disconnected, sharply while preserving portion of the CT plexus medially, You can see the medial wall of the trigonal that was affected by the smell formation further inspection makes me more satisfied that the malformation has been now addressed. The walls of the ventricles are preserved as much as possible without their injury. My indiscriminate coagulation. Post operative angiogram demonstrates gross total removal of the malformation without any complicating features. This patient did not suffer from any visual field deficit after her surgery. Thank you.
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