Loculated Intracranial Aneurysms: Angiography and Possible Etiology

Four-vessel femorocerebral angiography on 51 patients revealed 60 aneurysm of the circle of Willis or its major branches. Of these, 20 were multichambered or loculated and 10 had more than two chambers. Subarachnoid bleeding did not always occur, suggesting that loculations may represent areas of localized weakness on a parent aneurysm. Dye indicator studies on model aneurysms showed delayed dye retention beneath the aneurysm dome with turbulent flow, increased flow velocity, thicker aneurysm walls, increased pulse frequency, and smaller “necks.” Certain hemodynamic conditions could predispose to abrupt flow changes, resulting in aneurysm wall hypoxia, wall weakness, and regional loculation.