BACKGROUND: In patients with aneurysmal subarachnoid haemorrhage (SAH), headache 
typically is severe and often requires treatment with opioids. Magnesium has 
analgesic effects in several conditions, but whether it reduces headache after 
SAH is unknown.
METHODS: In a cohort of 108 SAH patients included in the randomised controlled 
trial Magnesium in Aneurysmal Subarachnoid Haemorrhage-II (MASH-II), severity of 
headache was regularly assessed on an 11-point scale until day 10 after SAH. 
Headache was treated according to a standardised protocol with acetaminophen, 
codeine, tramadol or piritramide. Serum magnesium levels were assessed every 
other day. Differences in mean headache scores between patients with mean high 
(>1.0 mmol/l) and normal (< or =1.0 mmol/l) magnesium levels were analysed with 
a Student t test. Crude and adjusted ORs for the use of codeine, tramadol and 
piritramide for patients with high versus normal magnesium levels were 
calculated with logistic regression.
RESULTS: The 61 patients with high magnesium levels had lower mean headache 
scores (4.1) than the 47 patients with normal magnesium levels (4.9; mean 
difference, 0.8; 95% CI 0.1 to 1.6) and required less tramadol (adjusted OR, 
0.3; 95% CI 0.1 to 0.7) or piritramide (adjusted OR 0.2; 95% CI 0.1 to 0.5). 
There were no differences in the use of acetaminophen or codeine.
CONCLUSION: In SAH patients, elevated serum magnesium levels are associated with 
slightly less severe headache and less frequent use of opioids. These data imply 
that intravenous magnesium therapy, besides a supposed beneficial effect on 
outcome, also provides pain relief for SAH patients, for whom it might also 
improve functional outcome.