Magnesium, one of the essential trace elements, plays important roles in 
maintaining both normal cellular and body functions. S100 calcium-binding 
protein B (S100B) has been used as a marker of glial damage in several 
neurological disorders. Thirty patients with ruptured intracranial aneurysms 
treated by clipping are included. The patients were randomized within 4 days 
after the attack of hemorrhage. The patients were divided into two groups with 
15 patients in each group. Group I received magnesium infusion within 4 days. 
Group II is the control group. World Federation of Neurological Surgeons, 
Fisher, and Glasgow outcome scores are evaluated at an intensive care unit in 
addition to 3 months clinical follow-up evaluation. Samplings of serum S100B 
were performed on admission and on postoperative days 1, 3, and 7. There is a 
statistically significant difference between both groups as regards the second 
reading of the S100B (day 1 postoperative; P < 0.05). There is no statistically 
significant difference between both groups as regards outcome at 3 months using 
clinical status and S100B values. There is a tendency in the magnesium group to 
have better outcomes. Further studies with more number of patients with 
subarachnoid hemorrhage are needed to determinate the accuracy of S100B protein 
as a prognostic marker and of magnesium sulfate as a neuroprotector.