Introduction: Shunt-dependent hydrocephalus (SDHC) after aneurysmal subarachnoid hemorrhage (aSAH) is the occurrence of symptomatic ventriculomegaly requiring permanent shunt diversion. Although several studies investigated the predictors of SDHC, the role of many of these factors, as well as the prevalence of SDHC and patients' clinical outcome, remain a matter of controversy.
Evidence acquisition: According to PRISMA guidelines we performed a systematic search looking into four databases with the purpose of clarifying the prevalence of SDHC after aSAH, the predictors of SDHC, the mortality rate and clinical outcome of patients with and without SDHC.
Evidence synthesis: Our analysis included 23 studies involving 22,264 patients. The overall prevalence of SDHC was 22.3% (95% CI: 17.9-26.6%). The predictors of SDHC included radiological hydrocephalus at presentation (OR 6.3, 95% CI: 2.27-17.51%), external ventricular drainage insertion (OR 5.7, 95% CI: 3.77-8.61%), high Hunt and Hess scale score (HHS 3-5: OR 3.3, 95% CI: 2.64-4.15%; HHS 4-5: OR 3.2, 95% CI: 2.4-4.2%), high Fisher grade (OR 3.1, 95% CI: 2.58-3.72%), intraventricular blood (OR 3.1, 95% CI: 2.60-3.71%), vasospasm (OR 1.9, 95% CI: 1.30-2.81%), intraparenchymal hemorrhage (OR 1.8, 95% CI: 1.2-2.78%), female gender (OR 1.3, 95% CI: 1.14-1.65%) and posterior circulation aneurysms (OR 1.4, 95% CI: 1.11-1.71%). The modality of aneurysm repair did not affect the rate of permanent shunt diversion. Patients with SDHC were more likely to be associated with a poor clinical outcome (mRS 3-6) (OR 4.3), even if mortality rate was similar between shunted and non-shunted patients (9%, 95% CI: 2-16% vs. 10.8%, 95% CI: 3.2-18.5%) (P=0.09).
Conclusions: The prevalence of SDHC is 22.3%. Our analysis identified several predictors of SDHC that can assist clinicians in monitoring patients with an aSAH. Shunt dependency is not related to the treatment modality of the ruptured aneurysm, whereas the occurrence of SDHC is a predictor of poor clinical outcome.