Rupture of anterior communicating artery aneurysms during computed tomography angiography: description of the pathway for intraseptal and intraventricular hemorrhage.

Intraventricular hemorrhage is common after the rupture of anterior communicating artery (ACoA) aneurysms, although the anatomical pathway has not been described. Knowledge of the mechanism of hemorrhage may enhance understanding of its prognosis. Using CT angiography, the authors analyzed this pathway in 2 cases of ACoA aneurysm rupture associated with intraventricular hemorrhage. The initial hemorrhages created a hyperdense ventriculographic image on which the subsequent contrast medium ejection could be followed. The contrast medium entered the subarachnoid space of the anterior interhemispheric fissure and broke through the lamina rostralis into the septum pellucidum and into the frontal horns of the lateral ventricles. Thus, the authors provide an explanation for bleeding from ACoA aneurysms into the ventricular system in the presence of an intact lamina terminalis. The septum pellucidum may act as a buffer before extension of the bleeding into the ventricular system.