The puzzling title “stroke and migraine: a cardiologists’ headache” conjures up a potential common cause: a cardiac right-to-left shunt through a patent foramen ovale (PFO). In the 16th century the Italian surgeon Botallo first described the PFO and in 1877 the suspicion of a PFO mediated stroke was published by the German pathologist Cohnheim. Since then the prevalence of PFO in adults has been established by autopsy studies (20–35%),1 2 transthoracic echocardiography (7–24%),3 4 or by the more sensitive transoesophageal echocardiography (20–40%).5^–7 The first major clinical paper associating PFO and stroke appeared in 19883 and the first reporting percutaneous closure in 1992.8

Migraine came into play rather accidentally when migraineurs were subjected to transcranial Doppler examinations and showed an increased prevalence of right-to-left shunt,9 and when a pronounced decrease in migraine symptoms was found in a series of patients undergoing atrial shunt closure for other reasons.10

All that remains to do now is to get the facts straight and rid our patients of such strokes and headaches—a task complex enough to constitute (hopefully transiently) a cardiologist’s headache.

EMBRYOLOGY, ANATOMY, AND PHYSIOLOGY

The PFO is an essential feature of intrauterine life (fig 1). Until birth and inception of breathing and pulmonary gas exchange, the PFO acts like an atrial septal defect (ASD), stays permanently open, and allows the right atrium receiving oxygenised blood from the placenta to unload directly into the left atrium. The flow through the pulmonary circulation is minimal due to the high flow resistance in the still collapsed lungs. With the first breath, the pulmonary resistance markedly drops and hence the right atrial pressure falls below the left atrial pressure. This moves the flail septum primum against the robust septum secundum, forming the cranial limbus of the fossa ovalis. Normally the two septa …