Angiogram-negative subarachnoid hemorrhage: Is it a correct definition?

Dear Editor, Spontaneous, nontraumatic subarachnoid hemorrhage (SAH) is a significant clinical problem thatmost commonly occurs as a result of aneurysm rupture [4]. In approximately 15 % of cases, no aneurysm or other vascular malformation can be identified as the origin of the hemorrhage by cerebral angiography [4]. In the English literature, over time, several definitions have been used to define these cases: idiopathic SAH or perimesencephalic nonaneurysmal subarachnoid hemorrhage (PN-SAH), angiogram-negative subarachnoid hemorrhage (AN-SAH), and nonaneurysmal SAH [2, 4]. AN-SAH is nowadays the widely accepted term for such nosological entities [2]. In 1985, Van Gjin et al. named this type of subarachoid hemorrhage as perimesencephalic subarachnoid hemorrhage because of its anatomical blood distribution [8]. This definition was insufficient to describe those cases in which the hemorrhage extended to the carotid cisterns, Sylvian fissure, and/or interhemispheric fissure [7]. For this reason, the definition of AN-SAH has been popularized by the relevant literature. As a matter of fact, AN-SAH is definitely used as the prevalent and widely accepted definition in the medical literature [1]. But is it the best definition? We report two cases in which spontaneous SAH revealed an aneurysmal malformation that was clearly not responsible for the subarachnoid bleeding. Can these cases still be defined as AN-SAHs?