**Abstract**

Hydrocephalus (HCP) occurs due to the injurious effect of subarachnoid haemorrhage (SAH). It causes increased morbidity and mortality. It can be acute and frequently occurs within 48 hours and up to 7 days. Subacute hydrocephalus may occur up to 14 days and is chronic if remained or develops after 2 weeks of the subarachnoid haemorrhage. Acute hydrocephalus after aneurysmal subarachnoid (aSAH) bleeding is non-communicating or obstructive and occurs due to physical obstruction by a clot, the effect of blood in the subarachnoid space, and inflammation. Chronic hydrocephalus is due to fibrosis and adhesion, which hampers cerebrospinal fluid (CSF) absorption and increased secretion of CSF from gliosis. Various risk factors for developing hydrocephalus in aneurysmal subarachnoid haemorrhage patients range from female gender to high severity scores. Acute hydrocephalus frequently requires diversion drainage of CSF by external ventricular drain (EVD); it usually subsides within a week, and EVD is removed. Fewer patients will develop or continue to have hydrocephalus, requiring either short or longer shunting of the CSF namely by ventriculoperitoneal shunt or other modes of CSF drainage.

**Keywords:** aneurysmal subarachnoid haemorrhage, cerebrospinal fluid (CSF), hydrocephalus, communicating, non-communicating, external ventricular drain (EVD), ventriculoperitoneal (VP) shunt
