**1. Introduction**

Subarachnoid haemorrhage (SAH) is blood in the space between the arachnoid membrane and pia matter around the brain (subarachnoid space). Hydrocephalus after aSAH (aneurysmal subarachnoid haemorrhage) is a frequent complication that can be acute, subacute, or chronic, requiring a diversion procedure such as external ventricular drain (EVD) or ventriculoperitoneal shunt insertion.

Up to 85% of subarachnoid haemorrhage occurs due to the rupture of a cerebral aneurysm, and SAH (subarachnoid haemorrhage) accounts for 5% of strokes. The overall incidence of aneurysmal subarachnoid bleeding is decreasing trend. However, aSAH (aneurysmal subarachnoid haemorrhage) remains a devastating clinical emergency with increased morbidity and mortality. aSAH varies according to geographic variation, with Finland and Japan having higher cases of SAH [1].
