PFO and Migraine
There is speculation that a PFO (a patent foramen ovale), which is a certain type of abnormal passage in the heart, might be related to migraine headaches. The foramen ovale is a passage through the upper chambers of the heart (the atria) from right to left. This passage is normally present before birth and then usually closes after birth. It continues to remain open (patent) in an many as 25% of the population. This causes a circumstance in which venous blood is able to bypass the lungs and cross directly into the left side of the heart, thereby entering the arterial circulation. This tendency is exacerbated when a person performs a valsalva maneuver - that is - puts pressure on the thorax while holding the breath such as might occur if a person lifts a heavy item, blows up a balloon, strains while having a bowel movement, or coughs. How is patent foramen ovale associated with migraine?There have been many isolated reports regarding people who happened to have migraines who have undergone closure of a patent foramen ovale for other reasons. These patients reported fewer or no migraines after the procedure, and so physicians began speculating as to why this might have helped.PFO appears to be most strongly associated with patients who have migraine with aura or who have very frequent migraines. A study performed by Dr. Silberstein found that in patients with chronic migraine (having greater than 15 migraine headache days per month for more than three months) 66% of them had evidence of PFOs (compared to the 25% found in the general population). In addition, patients who have migraine with aura seem to have a greater chance of having white matter lesions (small abnormal areas often visible on brain MRI) and seem to have a small increased risk of stroke. Some skepticism about these associations has been expressed by Dr. Fogoros (a cardiologist and expert commentator for
About.com
). He indicates that patent foramen ovale is easy to find in a well-studied population. That is, if you start with the condition (migraines) and look hard for patent foramen ovale, you will find more of it, because you are looking harder. If you then compare this rate of finding PFO with the 'background rate', you then discover a (false) association.
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Unfortunately, the 2008 update with regard to the MIST trial is as follows: (1) The data are now in question as one of the former principal investigators feels the data was analyzed incorrectly and (2) the re-analysis of the data indicates, at least for the device being used, no positive effect on migraines. It is possible that this particular device was not effective in closing the patent foramen ovale well, as some early reports indicated, but now we are left with no good randomized trial to support the concept of closure. It was because of the early results of this trial that other PFO closure trials were started and are continuing. Now we must wait for them to be completed to see if there will be any good evidence to support PFO closure for migraine. How could PFO cause migraine?It is really just speculation as to how or why patent foramen ovale would be related to migraine. One theory is that some substance that is normally filtered out by the lungs is allowed to cross into the arterial circulation. One more specific speculation is that platelets (the tiny cells that help blood to form blood clots) become 'activated' and form microaggregates (clumps of platelets) which might normally be cleared by the lungs. Instead, some of them are able to pass through the patent foramen ovale and into the brain. While these platelet aggregates do little harm, they might stop long-enough in the brain capillaries to cause local inflammation and trigger a migraine headache (in those patients who are already prone to getting migraines).How are PFOs diagnosed?2D-Echocardiogram: This is common way of diagnosing a patent foramen ovale. In this test, an ultrasound probe is placed on the chest and the important structures of the heart can be identified. Part of the test, called color doppler analysis, may reveal evidence of the patent foramen ovale. A more sensitive method is to inject agitated saline (containing tiny harmless bubbles) into a vein while the echocardiogram is being performed. If a patent foramen ovale exists, the bubbles can be seen traversing the division (the septum) between the atria of the heart.Transesophageal Echocardiogram: Another way of detecting a patent foreman ovale is to have a patient undergo a more intense echocardiogram during which a patient is sedated while an ultrasound probe is inserted into the esophagus. The heart structures can then be revealed in greater detail than when view through the chest. TCD with bubble study: The most sensitive technique for identifying PFO is combining the injection of agitated saline (containing tiny bubbles) with ultrasound of the brain arteries (transcranial doppler). How can PFO be treated?Currently, when it comes to chronic migraine, there isn't enough evidence for most neurologists to recommend patent foramen ovale closure. But in case you are curious, it can be treated through:Open heart surgery. This would involve opening the heart surgically and directly suturing closed the hole in the atrial septum. Transcatheter closure: This would be by far the more favored approach by both physician and patient and is the technique used in the MIST trail, see above. In this approach, a wire catheter is inserted into a large vein in the leg and threaded up the inferior vena cava (the largest vein in the body) while frequent x-rays (fluroscopy) are taken to observe the locations of the tip of the wire. The wire is inserted through the patent foramen ovale and a semi-rigid flat piece of material is opened, like an umbrella, in the left side of the heart. The same is done on the right side of the heart. The two flat pieces are then pulled together effectively closing the hole. Over time, the lining that covers the inside of the heart (the endothelium) grows over the device. Return from PFO AND MIGRAINE to MIGRAINE HEADACHES
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