Subarachnoid Hemorrhage Causing Hydrocephalus: Narrative Review of a Neurosurgical Emergency.

Hydrocephalus is a common complication following aneurysmal subarachnoid hemorrhage (aSAH) and remains one of the most frequent causes of readmission in patients with subarachnoid hemorrhage (SAH). If left untreated, hydrocephalus may lead to significant neurological deterioration and can be fatal; therefore, it represents a neurosurgical emergency. This review summarizes the current understanding of hydrocephalus following SAH based on the available literature. Hydrocephalus occurs in approximately one third (1/3) of patients with SAH. Depending on the timing of onset, it can be classified as acute, subacute, or chronic hydrocephalus. The underlying pathophysiology is multifactorial and includes obstruction of cerebrospinal fluid (CSF) circulation by blood clots and blood degradation products, impaired CSF absorption due to inflammation and fibrosis, and in some cases increased CSF production.  Diagnosis is primarily based on clinical deterioration and neuroimaging findings, with computed tomography (CT) of the brain remaining the gold standard for detecting ventricular enlargement and confirming the presence of hydrocephalus.  Management of acute hydrocephalus mainly involves CSF diversion, most commonly through external ventricular drainage (EVD). In some patients, hydrocephalus may persist and progress to a chronic form requiring permanent CSF diversion with ventriculoperitoneal (VP) or lumboperitoneal (LP) shunts. Hydrocephalus following SAH is associated with increased mortality, prolonged hospitalization, and long-term neurological impairment, emphasizing the importance of early diagnosis and timely management to improve patient outcomes.