Perianeurysmal edema after coil embolization of a giant ruptured aneurysm: illustrative case.

BACKGROUND: Perianeurysmal edema (PE) is a rare complication associated with treatment of intracerebral aneurysms; however, its mechanism is unclear. OBSERVATIONS: A 44-year-old woman presented with severe headache and nausea. Her imaging study showed a subarachnoid hemorrhage (Fisher group 2) due to rupture of a giant aneurysm of the left internal carotid artery. She underwent emergent coil embolization. However, she exhibited visual disturbance in her left eye that progressed a few days after the treatment. MRI revealed that the treated aneurysm developed into a partially thrombosed giant aneurysm with perifocal edema, and the mass compressed the left optic nerve. Oral prednisone was initiated, but her symptoms worsened. She finally underwent a flow diverter treatment 28 days after the endosaccular coil embolization and made a full recovery. LESSONS: The authors have reported a case of a ruptured giant aneurysm associated with PE after coil embolization. Although the mechanism of the edema remains uncertain, flow diverting stents should be considered as a potential treatment for PE following coil embolization of the aneurysm when indicated. https://thejns.org/doi/10.3171/CASE25560.