The distribution of subarachnoid and intraventricular hemorrhage on computed tomography suggests the location of an idiosyncratic vascular lesion

The incidence of aneurysmal subarachnoid hemorrhage (SAH) associated with intraventricular hemorrhage (IVH) varies. In general, the anterior communicating artery and posterior circulation aneurysms cause such IVHs. A 48-year-old man visited the Neurosurgical Department for the evaluation of a severe thunderclap headache that had awakened him from sleep. Brain computed tomography revealed diffuse, but asymmetric, SAH. Digital subtraction cerebral angiography (DSA) showed multiple vascular lesions, including an obvious saccular aneurysm on the left anterior choroidal artery. After surgical clipping, rebleeding was noted, and repeat DSA demonstrated that the bleeding site was on the right posterior cerebral artery. The distribution of SAH associated with the preserved Liliequist membrane may suggest the origin of the bleeding. Treatment of the correct bleeding site is effective for preventing rebleeding.