Moyamoya Disease Presenting as Subarachnoid Hemorrhage without Cerebral Aneurysm

Abstract Background: Moyamoya Disease (MMD) is a rare cerebrovascular disease caused by progressive stenosis or occlusion of the distal portion of the internal carotid arteries and/or the major cerebral arteries that arise from it. The stenosis triggers the development of an abnormal network of compensatory vessels to maintain cerebral blood flow. Subarachnoid hemorrhage (SAH) is a rare presentation of MMD, and non-aneurysmal subarachnoid hemorrhage is extremely rare, with only six previously documented cases worldwide. Our case report is an example of this extremely rare case presentation. Case Description: In this report, we describe the case of a 52-year-old male who suddenly developed severe headache and loss of consciousness after sexual intercourse. CT scan revealed SAH over the left frontal and temporal cortex. Cerebral angiogram demonstrated no aneurysm, but high grade narrowing of the left middle cerebral artery (MCA) and collateral blood flow from surrounding cerebral arteries consistent with moyamoya disease. The patient was managed medically throughout his hospital course and remained neurologically intact with no further hemorrhagic events. He was referred to neurosurgery outpatient for evaluation of revascularization surgery. Conclusions: Non-aneurysmal SAH in moyamoya disease is extremely rare. The evidence from this case, as well as the literature, supports the hypothesis that it is due to rupture of fragile transdural anastomotic vessels on the brain surface as they traverse through the subarachnoid space. An understanding of this unique mechanism of disease is valuable not only for tailored management, but also for considerations in surgical approach to revascularization.