Acute hydrocephalus associated with aSAH is usually managed by external ventricular drainage (EVD) or lumbar drainage. EVD for patients with aSAH-associated hydrocephalus is generally associated with neurological im- provement.246 249 The risk of aneurysm rebleeding with EVD has been studied in 3 retrospective case series, 1 of which found a higher risk of rebleeding with EVD,250 whereas the other 2 studies found no increased risk.239,251 Lumbar drainage for the treatment of aSAH-associated hydrocephalus has been reported to be safe (no increase in the risk of rebleeding), but it has only been examined in retro- spective series,214,252 255 1 of which specifically evaluated intraoperative lumbar drainage for brain relaxation.256 The theoretical risk of tissue shift after placement of a lumbar drain in patients with severe intracranial hypertension should be considered when deciding what method of cerebrospinal fluid diversion to use, particularly in patients with associated intraparenchymal hematomas. When obstructive hydroceph- alus is suspected, an EVD should be preferred. Preliminary data have suggested that lumbar drainage is associated with reduced incidence of vasospasm.214,255 Serial lumbar punc- tures to manage acute aSAH-associated hydrocephalus have been described as safe, but this strategy has only been assessed in small retrospective series.239,257 Chronic hydrocephalus associated with aSAH is usually treated with ventricular shunt placement. Only a proportion of patients with aSAH-associated acute hydrocephalus develop shunt-dependent chronic hydrocephalus. 