Does foramen closure improve migraine?

12 Feb 08

A. During fetal development, the foramen ovale allows blood to flow from the right to left atrium, facilitating circulation of oxygenated blood. Anatomical closure usually occurs during early childhood but remains patent, maintaining a right-to-left shunt, in about one-quarter of the population.

There is persuasive evidence of an epidemiological link between migraine with aura and the presence and size of patent foramen ovale. However, there is no evidence for a link between this and migraine without aura. The prevalence of migraine with aura is very high in patients with patent foramen. Migraine with aura is present in 18 to 43% of people with right to left shunt, significantly higher values than in the general population of about 5%.

Migraine with aura prevalence increases with the size of the shunt, from 4% with small shunts to 25% with medium and 53% with large shunts. The prevalence of a foramen in migraine with aura is also higher than expected. Aura migraine attacks are postulated to occur in people with foramen by the passage of vasoactive substances, platelet emboli or paradoxical emboli through the right-left shunt to the brain, bypassing the lung filter and triggering the migraine aura.

Closure of the foramen by implantation procedure is used in stroke and decompression illness. Data indicates that closure may be highly effective in resolving or improving aura migraine attacks in these patients. Overall, 70 to 91% of patients reported resolution or improvement and very low adverse event rates were reported with experienced cardiologists. However, further data is required before closure can be recommended as a treatment for migraine with aura. The MIST trial was designed to provide grade A evidence for this and full results are expected shortly.

Dr Andy Dowson is director of the King’s Headache Service, King’s College Hospital, London