Multiple Intracranial Arterial Aneurysms: A Congenital Metameric Disease?

We reviewed the angiographic study and clinical charts of 398 consecutive cases of intracranial arterial aneurysms, involving adults and children in the last 11 years (1986–1997). Giant aneurysms, dissecting aneurysms, mycotic aneurysms, and fusiform aneurysm were excluded. From the 341 patients presenting so-called berry aneurysm disease, attention was paid to multiple aneurysm sub group. One hundred and thirteen cases were analysed and compared with a group of single AA (228 cases) from the same material. Three longitudinal embryological territories giving rise to cranial endothelial cells and media were used to regroup the aneurysm sites. Eighty four cases presented aneurysms in the rostral region (74%), 20 cases with aneurysms involving rostral and middle territories (18%), 1 case presented aneurysm involving the middle and caudal territories (0.9%), 5 cases had aneurysms in the rostral and caudal territories (4.4%) and three cases presented aneurysm involving rostral, medial and caudal territories at the same time (2.7%). No multiple group was located in the middle or caudal territories alone. When several arterial territories were concerned they were adjacent in 95.6% of cases. Multiple AA could therefore result from mesodermal/neural crest stem cell or focal endothelial cell defect within one or two (usually consecutive) embryonic segments. Mirror lesions would correspond to bilateral symmetrical impairment in the same territory or involvement of a group of cells with bilateral distribution. AA may result from a constitutional vasculopathy, later expressed with focal overproduction of the arterial wall without remodelling correction. Secondary mutations and triggers are likely to be needed to lead to such AA production.