Aneurysmal subarachnoid haemorrhage (SAH) accounts for only 3-5% of all strokes but has the highest morbidity and mortality rates among all types of stroke. Experimental studies have confirmed that magnesium inhibits excitatory amino acid (EAA) release, blocks N-methyl-D-aspartate (NMDA) receptors and prevents calcium from entering cells. These changes may minimise neuronal injury during episodes of cerebral vasospasm. / Based on the aforementioned biological evidence, a pilot study of magnesium sulphate (MgSO4) infusion for aneurysmal SAH was conducted. This pilot study indicated that MgSO4 infusion for aneurysmal SAH is safe and has the potential to improve clinical outcomes. The pilot study results are supported by the findings of other research groups. / In summary, our results do not support a clinical benefit of intravenous magnesium sulphate infusion in patients with acute aneurysmal SAN. / Studies were carried out to investigate the distribution of magnesium in the cerebrospinal fluid (CSF) and the brain after intravenous magnesium sulphate infusion. We found that magnesium sulphate infusion resulted in an 11% to 21% increase in CSF magnesium, which was sustained for at least nine days. We further investigated intracellular free magnesium using 31 P-MRS, in aneurysmal SAH patients receiving and not receiving intravenous magnesium sulphate infusion. Intravenous magnesium sulphate infusion was found to produce a significant increase (15.6%) in the level of intracellular free magnesium during the first week, which covered the time frame required for neuroprotection, to improve outcomes in patients with aneurysmal SAH. / Three hundred and twenty-seven patients with aneurysmal SAH were recruited and randomly assigned to receive magnesium sulphate infusion or a saline placebo for 10 to 14 days. In the primary outcome analysis, the proportions of patients with a favourable outcome at six months (Extended Glasgow Outcome Scale [GOSE] score of 5-8) were similar, 64% in the MgSO4 group and 63% in the saline group (OR 1.0, 0.7-1.6). In the secondary outcome analyses, there were also no significant differences between the two groups. Analysis of the plasma magnesium concentration levels did not suggest that higher levels of plasma magnesium concentration result in better clinical outcomes. / Wong Kwok Chu. / Source: Dissertation Abstracts International, Volume: 73-02, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 132-152). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.