Disappearing saccular intracranial aneurysms: do they really disappear?

SUMMARY: Evolution and natural history of cerebral aneurysms is a dynamic process. Spontaneous regression in size or complete disappearance of an aneurysm is a known phenomenon, more commonly noted in giant intracranial aneurysms. However, reappearance or regrowth of such aneurysms is rare with few anecdotal reports. We report a series of four cases including one giant aneurysm, which either disappeared or regressed on sequential angiograms. Regrowth or reappearance of two of these previously disappeared or regressed aneurysms was noted and endovascularly treated while the other two cases are being followed up. The decision to follow up was crucial considering the nature of the aneurysms to change in morphology under the influence of various hemodynamic factors.