The vasodilatory effect of intra-cisternal infusion of magnesium sulfate 
solution was evaluated in 10 patients with symptomatic vasospasm after 
aneurysmal subarachnoid hemorrhage (SAH) who underwent early clipping surgery. 
Cisternal drainage was installed in the prepontine and/or sylvian fissures. 
Carotid angiography was performed immediately after the onset of symptomatic 
vasospasm, then intra-cisternal infusion of 15 mmol/l magnesium sulfate in 
Ringer solution was started at 20 ml/hr and continued until day 14. Irrigation 
was performed from the cisternal tube (inlet) to the spinal drainage (outlet). 
The cerebrospinal fluid magnesium ion concentration (1.2 +/- 0.2 mEq/l) 
significantly increased after the infusion therapy (6.0 +/- 1.7 mEq/l, p < 
0.001). Repeat angiography showed vasodilatory effect on the spastic cerebral 
arteries at 3 hours after the infusion, especially in the arteries near to the 
site of cisternal drainage placement. The magnesium infusion also caused 
decreased mean arterial blood velocity in the spastic arteries in 6 of the 7 
measured patients (162 +/- 38 cm/sec to 114 +/- 42 cm/sec, p < 0.001). Finally, 
5 of the 10 patients achieved good recovery, 1 patient had moderate disability, 
1 patient became severely disabled due to meningitis, and 3 patients were 
vegetative or dead, due to failure of magnesium irrigation in 1 patient and 
advanced age in the other 2 (more than 80 years old). This preliminary study 
indicates that intra-cisternal infusion of magnesium sulfate solution has 
vasodilatory effect on the spastic cerebral arteries after aneurysmal SAH.