Subarachnoid haemorrhage

**Definition:** Subarachnoid hemorrhage (SAH) is defined as the accumulation of blood in the space between the arachnoid membrane and the pia mater around the brain, referred to as the subarachnoid space. SAH demonstrates as acute neurological dysfunction, and is often a devastating clinical event with substantial mortality and high morbidity among survivors. The classic presentation is often a sudden-onset, severe headache typically described as the "worst headache of my life". The etiology of SAH can be either nontraumatic (about 85% are secondary to aneurysm rupture) or traumatic in nature. This category is intended only for nontraumatic SAH.

**Exclusions:** - Traumatic subarachnoid haemorrhage - sequelae of subarachnoid haemorrhage