Percutaneous closure of patent foramen ovale reduces the frequency of migraine attacks

Schwerzmann et al [1] found that closure of patent foramen ovale (PFO) reduced the frequency of attacks by >50% in migraine patients with aura (MA+) and without aura (MA-). These authors suggest PFO closure for prophylaxis of migraine and recommend a prospective trial.

The incidence of migraine headache in patients in the year prior to PFO closure was twice the expected prevalence. [1] Stress is one of the most common precipitants of migraine attacks. [2] The cerebral and peripheral events associated with PFO in these patients [1] are significant medical occurrences correctable only by invasive intervention. To exclude event-related stress, the incidence of migraine attacks prior to the event, diagnosis of PFO, or both, must be determined.

Secondly, the >50% reduction of migraine attacks following PFO closure [1] is statistically significant but biologically debatable. The placebo responsiveness of patients with migraine is increased. Inclusion of migraine patients with as few as two attacks per month in the analysis [1] could represent an important confounding variable; the probability of comparable replication of low-frequency attacks during the pre-trial, run- in and trial periods is low. Migraine patients with less than four headache attacks per month for at least three prospective pre-trial months should not be considered suitable for trials of prophylaxis. Moreover, inclusion of a post-PFO closure period of six-months of antiplatelet therapy into a composite 12-month post-procedure headache frequency analysis, [1] increases the confounding effect.

The reason that a higher prevalence of right-to-left shunt (RLS) should prevail in migraine patients with PFO is unclear. Periodic RLS in PFO occurs only when the right atrial pressure or pulmonary circulation afterload intermittently exceeds that of the systemic circulation. Is the systemic circulation in migraine patients a relatively low-resistance system that permits intermittent RLS? This is important because propranolol lowers systemic blood pressure and afterload. Also, whereas the clinico-pharmacological similarities of MA+ and MA- outweigh their phenomenological differences, [3] in one study no therapeutic benefit of PFO closure was found in of MA- patients. [4] Thirdly, MA+ has been associated with both RLS and correction of left-to-right shunt in atrial septal defect. [5]

Fourthly, it is difficult to accept that paradoxical emboli are being repeatedly directed over months or years to the same cerebral site to produce consistently lateralizing headache. The importance of lateralization of headache cannot be overemphasized. [3]

Finally, the neuroprotective effect of CSD in cerebral ischemia is well known.

References

1. Schwerzmann M, Wiher S, Nedeltchev K, et al. Percutaneous closure of patent foramen ovale reduces the frequency of migraine attacks. Neurology 2004;62:1399-1401.

2. Blau JN, Thavapalan M. Preventing migraine: a study of precipitating factors. Headache 1988;28:481-483.

3. Gupta VK. Classification of primary headaches: pathophysiology versus nosology? Published electronic response to: Peatfield R. A revised classification of headache disorders. Available at: http://bmj.com/cgi/content/full/328/7432/119?etoc (22 January 2004).

4. Sztajzel R, Genoud D, Roth S, et al. Patent foramen ovale, a possible cause of symptomatic migraine: a study of 74 patients with acute ischemic stroke. Cerebrovasc Dis 2002;13:102-106.

5. Gupta VK. Closure of atrial septal defect and migraine. Headache 2004;44:291-292.