Despite less variability of its antiplatelet effect, we recognized that HTPR or LTPR of prasugrel measured by P2Y12 assay were not absent in endovascular treatment of intracranial aneurysms; thus, we decided to investigate the predisposing factors related to responsiveness to prasugrel in the neurointerventional field. The gene discussed is P2RY12; the disease is Dilatation of the cerebral artery.