“…In the literature, only several case reports have described the presence of dural or perimedullary arteriovenous fistulas (DAVF) [2,10,14,17,22,28,31,44,45,48] and cavernous malformations [1,4,7,15,20,[25][26][27]42] as a cause of angiogram-negative SAH. The incidence of a spinal origin of SAH has been reported on in only three articles: Walton [47] described three cases, including one spinal AVM in 312 angiogram-negative SAH, resulting in a incidence of SVM of less than 1 % of total SAH.…”