Comment

摘要

Spontaneous, nontraumatic subarachnoid hemorrhage (SAH) is a significant clinical problem that most 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].