[Recurrent cerebral aneurysm after successful clipping of aneurysmal neck].

Neck clipping has been widely believed to be one of the most reliable and typical treatment of the cerebral aneurysm. Recently we experienced two cases of recurrence of cerebral aneurysm several years after surgery, in spite of confirmation of perfect neck clipping not only by intraoperative inspection but postoperative angiographical studies. The histological findings demonstrated that the arterial wall at the clip edge changed into thinning, interruption, and atrophy both of the muscle layer and internal elastic lamina. Therefore, local fragility of the arterial wall adjacent to clip edge seemed to cause formation of a new aneurysm. In addition, we discussed the usefulness of riskless CT in postoperative follow-up study of the cerebral aneurysm.