The search for an effective neuroprotective agent has not been a fruitful one. We had high hopes for magnesium, but it failed both as a neuroprotectant after aneurysmal SAH (MASH-I, IMASH, MASH-II, MASH trials), and in the prehospital setting as a neuroprotectant when administered early after suspected ischemic stroke (FAST-MAG). The authors of this meta-analysis hypothesized that earlier treatment with magnesium after SAH may in fact be effective, but that prior trials administered it too late and were underpowered to show effect in the small numbers of patients who were treated earlier. 

Five trials comprising 1981 patients were included, and the patients were binned according to how long after symptom onset they received magnesium (<6 hours, 6-12 hours, 12-24 hours, >24 hours). FAST-MAG included 5 patients with SAH (as the criteria were clinical stroke symptoms), so these 5 patients were incorporated into this meta-analysis. The primary endpoint was poor clinical outcome (mrs 4-5) or death at 3-6 months, with a secondary endpoint of delayed cerebral ischemia (which was determined differently by each trial).

Unfortunately, no benefit was seen with early magnesium treatment after SAH with respect to either functional outcome or delayed cerebral ischemia. A possible criticism is that only 83 patients (of a total 1981) were in the <6 hour group. However, if there were a strong effect in this early group, we would expect to at least detect a trend in improved outcome, which there was not. So long, magnesium; on to the next!