INTRAVENOUS MAGNESIUM-SULFATE RELIEVES CLUSTER HEADACHES IN PATIENTS WITH LOW SERUM IONIZED MAGNESIUM LEVELS

Patients with cluster headaches have been reported to have low serum i onized magnesium levels. We examined the possibility that patients wit h cluster headaches and low ionized magnesium levels may respond to an intravenous infusion of magnesium sulfate. Thirty-eight infusions of magnesium sulfate were given to 22 patients with cluster headaches. Th e mean ionized magnesium level prior to 23 infusions which provided re lief for at least 2 days and enabled the patient to skip two or more a ttacks, was 0.521 +/- 0.016 mmol/L; this value was 0.561 +/- 0.016 pri or to 15 infusions which were ineffective. These latter 15 infusions w ere preceded by higher total magnesium levels. The ionized magnesium l evel prior to the 23 effective infusions was below 0.54 mmol/L in 19 p atients. Five of the 15 ineffective infusions were accompanied by basa l ionized magnesium levels below 0.54 mmol/L. In 76% of the infusions, there was a correlation between a response and an ionized magnesium l evel below 0.54 mmol/L. Nine patients (41%) obtained clinically meanin gful improvement. Spontaneous remissions and a placebo effect might ha ve accounted for some of the improvement. However, this should have ap plied equally to all patients, regardless of the ionized magnesium lev el. Measurements of ionized magnesium may prove useful in elucidating the pathogenesis of cluster headache and in identifying patients who m ay benefit from treatment with magnesium.