Parenchymal perianeurysmal cyst in the brain: case report.

Objective And Importance: Parenchymal perianeurysmal cysts are rare, and only seven cases have been reported. We present a case report with a 30 month follow-up on this topic. The possible etiopathogenetic mechanisms of cyst formation are discussed.

Clinical Presentation: A 54-year-old man with a 5-month history of headache and a computed tomography scan showing a giant parenchymal cyst located in the right temporal lobe with a mural enhanced nodule was admitted to our neurosurgical department with the diagnosis of cystic brain tumor. Magnetic resonance imaging followed by digital subtraction angiography identified the enhancing nodule as a large right middle cerebral artery aneurysm.

Intervention: Surgical treatment was performed; the aneurysm was clipped and the cyst evacuated. Postoperative digital subtraction angiography confirmed the clipping of the aneurysm at the neck. Serial magnetic resonance imaging controls showed the permanent collapse of the cyst.

Conclusion: Parenchymal perianeurysmal cysts are rare. In the presence of parenchymal cysts neighboring main vessels, the possibility of a perianeurysmal cyst should be considered. In regard to the etiopathogenetic mechanisms responsible for the cyst development, the action of multiple coexisting factors seems to be the most applicable.