Intravenous mannitol in status migrainosus treatment: a clinical case series.

Status migrainosus (SM) is defined as a severe migraine attack, usually poorly responsive to treatments, lasting more than 72 h. Recurrent SM predicts chronic migraine (CM) development in 83.7% of cases. There is evidence that in most unresponsive CM patients a sinus stenosis-associated raised intracranial pressure is causatively involved in migraine chronification. To test the hypothesis that SM may reflect a sustained rise in intracranial pressure, we tested the efficacy of a 3-day treatment with intravenous mannitol 18% 250 ml b.i.d. in seven subjects presenting with a SM unresponsive to common treatments, showing unilateral or bilateral sinus stenosis at magnetic resonance venography. Mannitol infusion induced the abrupt reduction or the disappearance of pain in all patients, at least along the 3 days of treatment. While the benefit was only observed during the days of treatment in two subjects, in the remaining five patients the time to the next headache was delayed between 20 days to 5 weeks after mannitol infusion. Due to the lack of any analgesic property of mannitol, our data indicate that in this series a rise in intracranial pressure was involved in SM causative mechanisms.