There was no significant difference in mortality rate at discharge (p = 0.328). A trend toward improved outcome as measured by the modifed Rankin Scale (p = 0.084), but not the Glasgow Outcome Scale (p = 1.0), was seen in the MgSO4 treated group. CONCLUSIONS: Analysis of the results suggests that MgSO4 infusion may have a role in cerebral vasospasm prophylaxis if therapy is initiated within 48 hours of aneurysm rupture.