Subarachnoid hemorrhage (SAH) is bleeding right outside of the brain tissue, between the pial and arachnoid layers covering the surface of the brain. About 85% of SAH are caused by the rupture of a brain aneurysm, ie a weak portion of blood vessels around the brain that results in ballooning out of the arterial wall. A visible aneurysm is not found despite adequate workup for the remaining 15% and these are called "spontaneous" non-aneurysmal SAH. Like other brain bleeds, SAHs are severe medical/surgical emergencies that require immediate treatment in specialized centers. The goals in acute SAH management are to identify the aneurysm and treat it with an intervention (either clipping or coiling) to prevent re-bleeding and careful observation in an ICU setting to prevent and treat complications such as vasospasm. 

With frequent use of non-invasive brain blood vessel imaging, unruptured asymptomatic brain aneurysms are more commonly found on CT Angiography and MR Angiography scans as well as catheter based angiograms. If such a pathology is found, getting official advice from a Neurosurgeon or Interventional Neuroradiologist who treat such patients is helpful to discuss the best management approach.