Flow diverter therapy for immunosuppressant-resistant vertebral artery fusiform aneurysm due to eosinophilic granulomatosis with polyangiitis: illustrative case.

backgroundEosinophilic granulomatosis with polyangiitis (EGPA) is a systemic small-vessel vasculitis characterized by the presence of asthma and eosinophilia. Because cerebral aneurysm formation induced by EGPA is a rare occurrence, there is no established treatment strategy for this condition. OBSERVATIONS: A 67-year-old female who was diagnosed with idiopathic eosinophilia 3 months ago developed de novo fusiform aneurysms in the left vertebral, left internal carotid, and bilateral superficial temporal arteries, as noted during a regular follow-up examination of a convexity meningioma. Pathological examination of the resected superficial temporal artery revealed eosinophilic granulomas, which led to the diagnosis of EGPA, as well as EGPA-induced aneurysm formation. As the partially thrombosed vertebral artery fusiform aneurysm enlarged, the compression of the medulla oblongata occurred despite intensive immunosuppressive therapy for 1 year. The patient underwent flow diversion therapy administered using the pipeline embolization device, resulting in complete disappearance of the aneurysm. LESSONS: Considering that the entire circumference of the aneurysmal wall is affected by necrotizing vasculitis, flow diverter therapy would be a reasonable and efficient approach for the treatment of EGPA-related aneurysms in cases in which the patient is nonresponsive to immunosuppressants.