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Medial PICA Aneurysms

December 09, 2015


Clip ligation of posterior inferior cerebellar artery or PICA aneurysms can be quite challenging, if the neck of the aneurysm is located more medially along the PICA. This is a young patient, a 41 year old female who presented with acute subarachnoid hemorrhage. And on CTA was noted to have a right-sided small, approximately five millimeter PICA aneurysm, which was responsible for her hemorrhage. You can see the configuration of the aneurysm neck compared to the PICA itself. The aneurysm is essentially a true PICA, aneurysm is mostly located along the origin of PICA. Endovascular intervention was known to be risky and was likely to place the PICA itself as risk and due to the young age of the patient, microsurgical intervention was deemed appropriate. The patient was placed in a lateral position, a hockey stick incision was used, as you can see here, for the performance of a right lateral suboccipital craniotomy. The shoulder was rotated out of the way, a lateral suboccipital craniotomy was completed. The condyle was not drilled away, but manual removal was extended just to level of the condyle. The C one was also not removed in this case. The dura was open, parallel to the lateral edge of the bony removal. The brain was noted to be quite at dermatis despite drainage of CSF through the external ventricular drain. You can see that significant manipulation of the cerebellum is necessary for any exposure of the vertebral artery. Arachnoid membranes along the cisterns are generously open to drain additional CSF. Here, you can see the distal aspect of the PICA, here is the vertebral artery at its entry point into the intradural space. I continued dissection along the vertebral artery from proximal to distal, as well as along the PICA distal to proximal until the origin of PICA is identified. Here is the lower cranial nerves, fixer attractors had to be used due to significant brain swelling, despite all the medical and external ventricular measures to decompress the CSF spaces. You can see the thick clot over the vertebral artery complicating our dissection. Combination of sharp and blunt dissection was used to evacuate the clot. Here's the, more proximal portion of the PICA, here's the clot that is being removed, using pituitary ron drawers. I stay just on the vertebral artery and follow the route of the vertebral artery. The more distal location of the vessel or medial location around the brain stem complicates dissection, requiring ample amount of dissection around the brain stem to reach the neck of the aneurysm. Here's continuation of my dissection along the vertebral artery that is located here. Here's the origin of PICA. The aneurysm should be just about here, so here's PICA just under the suction. Here's the vertebral artery going away from us, and here is the aneurysm itself and here is PICA again. Further dissection is necessary before any clip is placed because the neck of aneurysm more anteriorly is not exposed. Here's the aneurysm again, more revealed, blunt dissection of the clip or its deployment at this stage is prohibited because it could lead to rupture and neck injury. As the blades will be unable to be placed across the neck, that is not thoroughly dissected. Here's further dissection of the neck itself, part of the dome is also exposed as the centers in is quite small. Now I have to move just underneath the vertebral artery and continue further dissection to be able to dissect the entire neck of the aneurysm. Here's again, more medially along the vert. Here's placement of the temporary clip to allow more high-risk maneuvers for dissection of the neck. Here's the vert, here's the PICA, here's dissection along the lateral aspect so the distal vert is identified. However, as you can see at this juncture to distal vertebral artery is not clearly in view because it moves medially and somewhat anteriorly. Therefore an alternative plan is necessary for me to be able to find the distal vertebral artery before the clip is deployed. Here's a more direct view of the anatomy of the neck of the aneurysm and its configuration compared to PICA and proximal vert, at the tip of my arrow. I spend ample amount of time, now I moved just anterior to the neck, underneath the PICA and vertebral artery and assure a complete circum dissection around the neck of the aneurysm, an identification of distal vertebral artery before planning deployment of the aneurysm clips. Here is further dissection around the aneurysm. Here is the distal vert, you just saw a moment ago, dissecting along the thick clot. Here you'll be able to see the distal vert right there, a very hidden place, just anterior to the aneurysm. Here is PICA aneurysm, proximal vert, distal vert, all the three vessels that have to be identified are now in view. The aneurysm is ready for its clip. I can see the broad base and the true origin of the aneurysm neck from PICA. Again, further inspection of the entire anatomy around the neck is warranted before the clip blades are placed. Here's the distal vert, more evident and very clear. Here's the neck of the aneurysm underneath the PICA. The distal neck of the aneurysm is evident. Temporary occlusion is readily tolerated because of the contralateral flow from the vertebral artery. My curved clip was used just coming over the PICA, while keeping the distal clip blades in view, so that appropriate exclusion of the neck is possible. Here's the complete closure of the nick clip blades. The tip of the blade is all the way across the aneurysm neck. Micro doppler ultrasonography, assures exclusion of the aneurysm dome. Intraoperative ICG and fluorescein angiography, reveal exclusion of the aneurysm and preservation of all the parent and branching vessels. Here, you can see the dome of the aneurysm is dark and non-contrast enhancing. The ICG is somewhat not useful in this situation because of the small working distance and the unavailability of light to be able to excite the fluorescent contrast or the ICG within the vessels. However, fluorescein is more effective in this situation. Post operative cerebral arteriogram, demonstrates complete exclusion of the aneurysm without any complicating features or compromise of the PICA. This patient recovered from her subarachnoid hemorrhage and surgery without any untoward side effects. Thank you.

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