{"id":"307f0696-478a-4bcc-910e-871a29d6301f","slug":"a-large-peri-aneurysmal-cyst-formation-following-coil-embolization-of-an-unruptured-middle-cerebral-artery-aneurysm-a-case-report-and-review-of-the-literature","title":"A large peri-aneurysmal cyst formation following coil embolization of an unruptured middle cerebral artery aneurysm: A case report and review of the literature","authors":["Daiki Matsuda","Yushi Nagano","Hiroshi Hosoyama","Masaaki Yamamoto","Shunichi Tanaka","Sei Sugata","Ryosuke Hanaya","Kazunori Arita"],"abstract":"Background: Peri-aneurysmal cyst formation is a rare but serious complication that may develop after endovascular treatment. Case Description: A 72-year-old woman underwent endovascular treatment for an incidentally found oblong middle cerebral artery aneurysm measuring 17 mm in its largest diameter, resulting in complete obliteration. Peri-aneurysmal parenchymal edema, however, began to develop 1 year after the procedure. Follow-up magnetic resonance imaging revealed the emergence of a small cyst and a gradual increase in peri-aneurysmal edema in the basal ganglia. A susceptibility-weighted imaging showed hemosiderin deposition in the basal ganglia and cerebral cortices around the aneurysm. The cyst finally grew to 55 mm at 71 months after the initial treatment, causing headaches and cognitive dysfunction. Wide fenestration of the cyst wall, pathologically confirmed as gliosis, resulted in shrinkage of the cyst and rapid improvement of symptoms. Conclusion: A review of the literature identified 14 cases of symptomatic peri-aneurysmal cyst formation following coil embolization, including the present case. Based on this review, peri-aneurysmal cyst formation should be anticipated after repeated endovascular treatments for large aneurysms embedded in the brain, particularly when peri-aneurysmal brain edema develops. Continuing microhemorrhage from the aneurysm or vasa vasorum may play a role in the cyst formation.","thumbnailUrl":"https://sni-digital-videos.s3.amazonaws.com/articles/307f0696-478a-4bcc-910e-871a29d6301f/featured/hero-1781557509777.png","publishDate":"2026-05-15T00:00:00.000Z","doi":"10.25259/SNI_236_2026","categories":["Neurovascular","Case Report"],"fullTextUrl":"https://surgicalneurologyint.com/api/articles/307f0696-478a-4bcc-910e-871a29d6301f/pdf"}