**Abstract**

Non-traumatic subarachnoid hemorrhage is a devastating neurological emergency, the main cause of which is aneurysmal rupture. The treatment of the aneurysm, whether microsurgical or endovascular, is essential for the recovery of these patients, however, a series of pathophysiological events in the days following the bleeding cause great damage to the brain tissue. For many years efforts have been focused on the prevention and treatment of cerebral vasospasm, which is believed to be the cause of late cerebral ischemia. However, new pathophysiological perspectives point to a series of events that begin immediately after bleeding, known as early brain injury, mainly involving brain microvascular dysfunction, cortical spreading depolarizations and neuroinflammation, which we discuss below.

**Keywords:** subarachnoid hemorrhage, early brain injury, microvascular dysfunction, cortical spreading depolarizations, neuroinflammation
