Formation of new aneurysms. Report of five cases.

Among 964 patients diagnosed and treated for intracranial aneurysms in 5 evidence of formation of new aneurysms was found. Repeat angiography, performed after the second SAH, revealed new aneurysms on arteries normal on previous angiograms; there were multiple aneurysms in 3 cases. In 4 cases, the aneurysms were formed within 3 to 6 years. In the authors' opinion, the possibility of formation of new aneurysms after the cure of a demonstrable one, should be considered in all aneurysmal patients, especially in multiple cases. Possible mechanisms of development of new aneurysms are discussed.