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Papaverine – A drug that causes blood vessels to dilate. In the setting of severe vasospasm, a neuroradiologist may perform an angiogram and then inject papaverine into the narrowed arteries to help them dilate.

Parent Artery Occlusion – A procedure performed by a neuroradiologist or neurosurgeon in which an artery is permanently blocked to treat a cerebral aneurysm. In rare cases when neither clipping nor coiling is possible, aneurysms are treated by blocking the entire involved artery and aneurysm together.