TY - JOUR T1 - Refractory in-stent stenosis after flow diverter stenting associated with delayed cobalt allergic reaction JF - Journal of NeuroInterventional Surgery JO - J NeuroIntervent Surg DO - 10.1136/neurintsurg-2021-017948 SP - neurintsurg-2021-017948 AU - Shoko Fujii AU - Kyohei Fujita AU - Hiroto Yamaoka AU - Kazunori Miki AU - Sakyo Hirai AU - Shigeru Nemoto AU - Kazutaka Sumita Y1 - 2021/08/25 UR - http://jnis.bmj.com/content/early/2021/08/24/neurintsurg-2021-017948.abstract N2 - In-stent stenosis (ISS) triggered by a metal-induced allergic reaction of Pipeline embolization device (PED) placement is extremely rare. The present report describes a patient who presented with delayed parent artery occlusion and refractory ISS after PED placement due to cobalt allergy. A patient in her 70s underwent PED placement for a right internal carotid artery (ICA) large aneurysm; 4 months later, the patient presented with left-sided hemiparesis, and MRI revealed right ICA occlusion even though antiplatelet therapy was optimal. She underwent mechanical thrombectomy, and successful recanalization was achieved. However, follow-up angiography 6 months after the thrombectomy revealed severe ISS, and the patch testing showed a positive reaction for cobalt. As a result of long-term administration of oral steroids and antihistamine, progression of ISS was suppressed. It was supposed that a delayed hypersensitivity reaction to cobalt might induce refractory ISS after PED placement. ER -