CSF diversion after aneurysmal sub-arachnoid hemorrhage: towards personalized treatment strategies

Aneurysmal subarachnoid hemorrhage (aSAH) is a life-threatening condition associated with high morbidity and mortality, with survivors often experiencing long-term neurological and functional deficits. Cerebrospinal fluid (CSF) diversion plays a pivotal role in the acute management of aSAH, both for the treatment of hydrocephalus and for the prevention of delayed cerebral ischemia (DCI) through clearance of blood breakdown products. Four principal modalities are currently employed: lumbar puncture, lumbar, cisternal, and external ventricular drain. Each technique differs in its mechanism of drainage, monitoring capacity, complication profile, and influence on shunt dependency and long-term outcome. High-quality evidence from randomized controlled trials now supports lumbar drainage as the only intervention that significantly reduces the incidence of DCI and has been shown to improve functional outcomes, making it the preferred first-line approach in suitable patients. External ventricular drains remain indispensable in cases of obstructive hydrocephalus or reduced consciousness, while lumbar puncture may be considered in carefully selected low-risk patients. Cisternal drains represent a potential adjunct in those undergoing surgical clipping of the aneurysm. In patients without hydrocephalus, lumbar drains remain the only strategy with demonstrated long-term benefit. Given the heterogeneity of aSAH presentations and the limitations of existing evidence, individualized selection of CSF diversion techniques is warranted. We propose a pragmatic decision-making algorithm to optimize patient outcomes while minimizing iatrogenic complications, which can be adapted to institutional practices and further refined through prospective evaluation.