De novo aneurysm of the anterior communicating artery presenting with subarachnoid hemorrhage 7 years after initial cryptogenic subarachnoid hemorrhage: a case report and review of the literature.

Spontaneous subarachnoid hemorrhage (SAH) is usually caused by a ruptured cerebral aneurysm. Despite the use of initial four-vessel cerebral digital subtraction angiography (DSA), 15 % of all cases remain idiopathic. According to the initial computed tomographic scan, the spontaneous SAH can be divided into a perimesencephalic group associated with a benign nature and a nonperimesencephalic group with a similar clinical course as aneurysmal SAH. We present a case of a 49-year-old man with a de novo aneurysm formation of the anterior communicating artery with SAH 7 years after initial cryptogenic nonperimesencephalic SAH. This observation suggests that in some cases, long-term angiographic studies might be justified.