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Orbitofrontal and Frontopolar Aneurysms: Technical Challenges

August 17, 2016


This is an interesting case of a patient who was harboring two A2 aneurysms, one at the level of the orbitofrontal and one at the level of the frontopolar arteries. This patient previously underwent clip ligation of MCA aneurysm that was ruptured and these two other ACA aneurysms were found incidentally. After recovery from the initial MCA aneurysm rupture, the patient underwent clip ligation of this orbitofrontal and frontopolar arteries. You can see the origin of the orbitofrontal artery from the neck of aneurysm. The sagittal CT angiogram also localizes the location of these aneurysms. More specifically, an interhemispheric approach was the most appropriate for exposure of these aneurysms safely. The craniotomy involves bone removal just above the frontal sinus using a bicoronal incision. This 3D reconstruction of the angiogram further demonstrates the morphology of these aneurysms. Here's the bicoronal incision. The bone over the superior sagittal sinus was unroofed. The anterior interhemispheric fissure was entered. The frontal peel membranes are quite interdigitating. In this interior part of the anterior hemispheric space, dissection can be quite challenging and tedious, patience is required for preservation of the peel surfaces. I use the arteries as a roadmap. I follow the routes. You can see the frontopolar artery was readily exposed. Obviously the more proximal aneurysm has to be clipped first so the clip on the distal aneurysm is not interfering with clip placement on the more proximal aneurysm neck. I follow the A2's, brain appeared somewhat tense. I therefore exposed the anterior corpus callosum as you'll see in a moment and a small callosotomy was completed to drain some CSF. Again, here's the proximal aneurysm. Brain up here is somewhat tense. Here's exposure of the corpus callosum. Small callosotomy was created and CSF was removed to achieve brain relaxation. Here's the ependyma, equally serves CSF. Now that the brain is more relaxed, let's go back to dissection of the more proximal or orbitofrontal aneurysm. Small amount of brain or the neck of the aneurysm was removed more anteriorly. Here's the proximal neck. I still have to expose the origin of the orbitofrontal artery. Here you can see the origin just about there. The neck has to be generously dissected so that the clip blades are not advanced blindly. Here's the origin of the orbitofrontal artery, here's the neck of the aneurysm, here's more proximal A2. Now I prepare the part of the A2 just proximal to the neck so that the temporary clip can be placed. Placement of the temporary clip is important so that the neck of the aneurysm on the more medial side can be adequately dissected via deflation of the aneurysm sac. Here's a more demagnified view of our operative corridor. Here's an angle temporary clip, just proximal to the aneurysm neck. Working space is quite limited and the working distance is long. Here you can see the dissection of the other side of the neck so that the clip blades can be advanced readily. Here's the angled clip that was used in this case to go across the neck of the aneurysm while preserving the origin of the orbitofrontal artery. Fluorescein and ICG angiogram demonstrated complete exclusion of the aneurysm and patency of the branching vessels including the orbitofrontal artery. Next, I divert my attention toward the more distal frontopolar aneurysm, you can see the neck. One more time, the circumference of the neck of this aneurysm is also dissected adequately. Preparing soak gel foam was used to relieve spasm on the parent and branching vessels. Here's a temporary clip on the frontopolar artery. Dissection of the neck, just behind the aneurysm. Sharp dissection was utilized. This part of the aneurysm sac was very embedded within the peel. The aneurysm had to be completely mobilized so adequate exclusion of the neck can be performed. Here's the straight clip across the neck. Micro-Doppler ultrasonography revealed complete exclusion on the aneurysm with patency of the surrounding vessels and post operative angiogram revealed complete exclusion of both aneurysms and this patient made an excellent recovery. You can also again see the extent of the craniotomy based on the post-operative CT imaging, just above the frontal sinus. The post operative CT scan revealed no evidence of ischemia. Thank you.

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