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Large Partially Thrombosed ACoA Aneurysm with Chiasmal Compression

January 26, 2016


Here's a very interesting case of a large partially thrombosed, inferiorly pointing anterior communicating artery aneurysm, leading to symptomatic chiasmal compression. This is a patient of mine who primarily presented with evidence of visual decline and underwent visual field evaluation, which demonstrated visual field deficits. You can see the right eye is more affected than the left eye. This CT angiogram demonstrates a larger aneurysm with a smaller life or patent lumen. You can see the aneurysm is pointing from the right, toward the left side. Most likely A1 is dominant. An angiogram was performed, which confirmed the angio-architecture of the aneurysm. Here's an MRI also, that demonstrates the... Patent lumen of the aneurysm, associated with a thrombosed component. Again, the aneurysm is pointing inferiorly and affecting the optic chiasm. Let's review the cerebral arteriogram before we proceed with the surgery. You can see the dominant right, A1, leading to the aneurysm, and right frontotemporal craniotomy facilitate the exposure of the aneurysm via the subfrontal approach. Please note the turn of the head. Here's the extent of the cortical exposure, primarily frontal exposure, Sylvian fissure. I use a piece of rubber dam or a piece of cloth under the Cottonoid patty to slide around the subfrontal cortex, atraumatically. An orbitozygomatic craniotomy is unnecessary. Here's the optic chiasm that is deformed by compression and... Indentation of the aneurysm that is apparent at the tip of my arrow. Anterior limb of the Sylvian fissure was dissected and proximal control was secured. Dynamic retraction is quite effective, here's the ipsilateral A1 leading to the aneurysm, artery of Heubner, Ipsilateral A2, proximal control is readily available. The neck of the aneurysm, quite atherosclerotic. Let's go ahead and find the other components of the ACoA complex. Here's in view just underneath the A1, across the aneurysm. The aneurysm is quite embedded and adherent to the superior surface of the chiasm. Here's the artery of Huebner that is being released. So, further brain mobilization is possible. You can see the neck of the aneurysm all the way across, toward the A2, contralaterally. Again, please note the use of dynamic retraction. Here's the contralateral A1. A blister over the neck of the aneurysm. Interhemispheric fissure is dissected to clearly identify the ACoA complex. I use the fenestrated straight clip while mobilizing the perforator to close the distal neck of aneurysm. Obviously, the anterior communicating artery is protected. I suspect that a second clip would be necessary to completely collapse the aneurysm neck. You can see the clip has been gently inserted into its final position, without compromising the ACoA or the origin of ipsilateral A2. Further inspection reveals protection of the perforators, the clip is all the way across. An intraoperative fluorescence angiogram using fluorescein and ICG revealed some filling of the aneurysm, primarily along the proximal neck of the aneurysm as expected. I deployed a second clip just in front of the ipsilateral A2 to collapse the proximal portion of the neck of the aneurysm. Here's the final clip construct. You can see the ACoA is patent. The aneurysm was subsequently opened and debulked to relieve its mass effect on the optic chiasm. Since the aneurysm was very adherent to the chiasm, I did not dissect the dome of the aneurysm to prevent any injury to the optic apparatus. Here's an ultrasonic aspirator debulking the internal contents of the aneurysm sac. The live lumen of the aneurysm is reached. Again, the sac was quite adherent to the optic apparatus. The chiasm appears quite decompressed. Can see minimal amount of injury to the frontal cortices. Postoperative CT angiogram demonstrated adequate clip ligation of the aneurysm without any side effects, and this patient's vision improved significantly, immediately after surgery. Thank you.

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