"Small ghost aneurysm": delayed visualization of a ruptured thrombosed nonbranching M2 aneurysm with pathological and hemodynamic correlation. Illustrative case

Background: Ruptured thrombosed aneurysms may transiently disappear on angiography and later reappear after partial recanalization. The authors report a ruptured nonbranching M2 aneurysm with delayed angiographic visualization and pathological/hemodynamic correlation.

Observations: A 43-year-old man presented with diffuse subarachnoid hemorrhage (SAH). Initial CT angiography and digital subtraction angiography failed to identify the bleeding source. Serial follow-up imaging subsequently demonstrated delayed visualization of a small (3.5 mm) distal nonbranching M2 lesion on day 11 of angiography. Microsurgical reconstruction was performed with evacuation of organized thrombus, direct closure of the aneurysmal orifice, and preservation of parent artery flow. Histopathological examination demonstrated organized thrombosis with disruption of elastic fibers. Intraoperative indocyanine green videoangiography demonstrated preserved parent artery flow without apparent intra-aneurysmal flow despite angiographic visualization on the preceding day. Computational fluid dynamics analysis demonstrated disturbed local flow with focal stagnation and localized oscillatory flow.