BACKGROUND: A meta-analysis of current data suggests that magnesium sulfate 
infusion improves the outcome after aneurysmal subarachnoid hemorrhage through a 
reduction in delayed ischemic neurological deficit. Two multi-center randomized 
controlled trials are currently underway to investigate this hypothesis. The 
possible pharmacological basis of this hypothesis includes neuroprotection and 
vasodilatation. We aim to investigate the cerebral hemodynamic effects of 
magnesium sulfate infusion in aneurysmal subarachnoid hemorrhage patients.
METHOD: A total of 12 patients who had experienced aneurysmal subarachnoid 
hemorrhage were randomized to magnesium sulfate infusion (n = 6) or placebo 
infusion (n = 6) for 14 days. Each patient had two perfusion MRIs performed, one 
in the first week after subarachnoid hemorrhage and one in the second week after 
subarachnoid hemorrhage.
FINDINGS: Age, sex, and Fisher CT grade were not different between the two 
groups. All but one patient were of WFNS Grade I to II on presentation. There 
was no increase in rCBV, rCBF and MTT between the two perfusion scans within the 
same group or between the two groups.
CONCLUSION: Magnesium sulfate infusion, in the dosage of current clinical 
trials, did not increase cerebral blood volume and cerebral blood flow, as 
postulated by dilation of small vessels and/or collateral pathways.