De novo aneurysm formation after stereotactic radiosurgery of a residual arteriovenous malformation: case report.

We report a case of a 19-year-old woman who underwent radiosurgical treatment of a residual arteriovenous malformation. Nine months after treatment, repeat angiography revealed a de novo paranidal aneurysm that was treated endovascularly. We postulate that changes in flow dynamics or vessel integrity after radiosurgery contributed to the formation of her de novo aneurysm.