Non-aneurysmal Subarachnoid Hemorrhage in an Adult With Sickle Cell Anemia: A Case Report and Review of the Literature.

Moyamoya disease (MMD) is a rare, idiopathic cerebrovascular disorder characterized by bilateral stenosis of the internal carotid arteries (ICAs) and the formation of collateral vessels at the base of the brain. In patients with sickle cell disease (SCD), chronic vaso-occlusive changes can produce moyamoya-like vasculopathy, resulting in moyamoya syndrome (MMS) and increasing the risk of aneurysm formation and rupture. Nonetheless, presentation of MMS as non-aneurysmal subarachnoid hemorrhage (NASAH) is extremely rare, with few reported cases. Our case is about a 28-year-old male, a known case of SCD, who developed NASAH. He presented with a sudden decrease in consciousness, severe headache, nausea, and vomiting. Emergency evaluation revealed significant neurological impairment. Unenhanced brain computed tomographic imaging showed pure intraventricular hemorrhage. Computed tomographic angiography revealed the absence of contrast filling in both ICAs at the level of bifurcation, with prominent posterior circulation. Suspicion of MMS was raised. Diagnostic cerebral angiography revealed a complete absence of the right ICA and an almost completely occluded left ICA terminating at the anterior communicating artery (Acom). A run-through vertebral artery injection revealed the classic "puff of smoke" appearance, confirming the diagnosis of MMS. The patient was managed conservatively with the SAH protocol and was admitted to the intensive care unit. The patient passed away after a complicated course with multiple stroke events. MMD presenting as NASAH is uncommon and is believed to result from rupture of fragile vessels associated with MMD. This case supports previous findings, highlighting the importance of recognizing this presentation for timely management.