PTGS2 and Dilatation of the cerebral artery: Hasan et al. demonstrated in a small group of patients who cyclooxygenase-2 (COX2) and microsomal prostaglandin synthase E2-1 (mPGES-1) are expressed in human intracranial aneurysms, and their expression increases with aneurysm rupture, which can be blocked by ASA [23].