case_images: PMC11225393_01
case_images: (a and b) Initial computed tomography (CT) shows severe subarachnoid hemorrhage with a mass lesion in the interhemispheric fissure, and CT angiography shows a large ruptured cerebral aneurysm in the anterior communicating artery. (c) Postoperative cerebral angiography reveals that endovascular treatment achieved adequate coiling with a small neck remnant. (d) Follow-up cerebral angiography 27 months after initial treatment shows recurrence of aneurysm and enlargement of neck remnant.
case_images: SNI-15-189-g001.jpg
case_images: PMC11225393_01_SNI-15-189-g001.jpg
case_images: F1
case_images: Detachable Coil -18 360 [Boston Scientific, Fremont, California, USA] and Target 360 standard [Stryker, Kalamazoo, MI, USA]). Due to the risk of parent artery occlusion, a small neck remnant remained [Figures 1a-c]. However, additional endovascular treatments for the enlarged neck remnant were required at 27 and 35 months after the initial treatment [Figure 1d].
case_images: (a and b) Magnetic resonance image (MRI) 24 months after the initial treatment shows that the cystic lesion developed from just above the coiled aneurysm (a and b). (c) Cerebral angiography reveals that there is no blood flow into the perianeurysmal cyst and no recurrence of cerebral aneurysm. (d and e) MRI just before endoscopic treatment shows that an enlarged perianeurysmal cyst led to obstructive hydrocephalus and progressive parenchymal edema.
case_images: SNI-15-189-g002.jpg
case_images: PMC11225393_01_SNI-15-189-g002.jpg
case_images: F2
case_images: During this treatment course, a perianeurysmal cyst developed immediately above the aneurysm without any additional clinical symptoms 24 months after the initial treatment [Figures 2a and b]. Cerebral angiography revealed no blood flow from the cerebral aneurysm to the perianeurysmal cyst [Figure 2c]. Magnetic resonance imaging (MRI) revealed an enlarged perianeurysmal cyst occluding the foramen of Monro, and parenchymal edema was observed on fluid-attenuated inversion recovery imaging [Figures 2d and e].
case_images: (a) Intraoperative findings. The lesion is revealed through an endoscopic approach from the left anterior horn. The cyst wall was composed of a tight and fibrous layer and obscured the foramen of Monro (white arrow). (b) The fibrous cyst wall is widely opened. A coiled cerebral aneurysm (asterisk), optic chiasma, and left optic nerve are observed from the inside of the perianeurysmal cyst. (c) Hemosiderosis is often seen in the cyst wall (white arrowhead). (d) After cyst fenestration, the left foramen of the monro was opened, and the third ventricle was preserved under the cyst. Acom: Anterior communicating artery, ON: Optic nerve, TV: Third ventricle, FOM: Foramen of Monro, V: vein.
case_images: SNI-15-189-g003.jpg
case_images: PMC11225393_01_SNI-15-189-g003.jpg
case_images: F3
case_images: Finally, in the same manner, two points of fenestration were achieved, avoiding the wall vein and confirming the patency of the Monro foramen [Figures 3a-d].
case_images: Histopathological findings. (a) Hematoxylin and eosin (HE) staining shows that the cyst wall is focally covered by monolayered flat or columnar epithelium, associated with aggregates of siderophage material. There is no inflammatory cell infiltration into the cyst wall. (b) Immunohistochemistry and Masson-trichrome staining show fibrous changes under the ependymal layer. (c) No blood vessels are detected in the Elastica van Gieson stain. (d) The cyst wall is also positive for Glial fibrillary acidic protein.
case_images: SNI-15-189-g004.jpg
case_images: PMC11225393_01_SNI-15-189-g004.jpg
case_images: F4
case_images: Histopathological examination revealed that the cyst wall was composed of eosinophilic fibrous tissue covered with a monolayer of ependymal cells, and no neovascularization was observed within the cyst wall [Figures 4a-d].
case_images: Follow-up MRI 18 months after treatment shows no recurrence of the perianeurysmal cyst and improvement of parenchymal edema.
case_images: SNI-15-189-g005.jpg
case_images: PMC11225393_01_SNI-15-189-g005.jpg
case_images: F5
case_images: At the 18-month follow-up, there was no significant recurrence of the perianeurysmal cysts or obstructive hydrocephalus [Figure 5].