[Multiple intracranial aneurysms and asymmetrical circle of Willis].

In a consecutive series of 268 patients harboring saccular aneurysms confirmed by digital subtraction angiography (DSA) all major blood vessels of the brain, 36 patients (13.4%) with multiple aneurysms were identified. Majority of them (around 58%) were between 40 to 60 years of age, around 22% were below 40 years of age, but no was younger than 30 years of age. The asymmetric Willis circle was identified in 26 patients (74.2%) A hypoplastic A1 segment of the anterior cerebral artery was revealed in 10 patients; a combination of the hypoplastic A1 segment and the fetal type of the posterior communicating artery with a hypoplastic P1 segment of the posterior cerebral artery were found in 9 cases, while 7 patients had only the fetal posterior communicating artery. A suggestion was put that the asymmetric circle of Willis, prenatal or acquired in postnatal life is inclined of developing aneurysm (multiple aneurysms) only if there exist a hemodynamic stress in postnatal life producing degenerative lesions of the circle of Willis at the site of the augmented hemodynamic vascular wave.