Page 77 - Migraine, the heart and the brain

Right-to-left shunts and micro-embolization in migraine
introduCtion
Since 1998, several studies have reported on the increased prevalence of right-to- left shunt (RLS) in patients with migraine with aura, but not in migraine without aura [1 – 4]. The biological mechanism linking RLS and migraine with aura remains speculative. There have been several retrospective and uncontrolled studies, also recently, indicating promising effects of closure [5 – 9], but a robust effect of shunt closure on migraine severity has not been shown in the single randomized controlled trial published back in 2008 [10].
Several questions remain. First, migraine with aura and a RLS are associated but is
this a causal relation, and if so by what biological mechanism? Second, does closure of 4 the RLS bene t the migraine patient? The aim of the current article is to answer these
questions and comment on whether diagnosing RLS in migraine patients should be
advised in clinical practice or not.
Background
A RLS is an abnormal communication between the right (venous) circulation and the left (arterial) circulation. Several structural abnormalities can cause right-to-left shunting; the most frequent cause is a patent foramen ovale (PFO) [11,12], a remnant from the fetal period that is located in the atrial septum of the heart. Other causes of RLS are atrial and ventricular septal defects and arteriovenous malformations or stulae (PAVMs) at the pulmonary level [13]. When comparing publications on this subject, one should distinguish between the various types of RLS investigated. We will review the relationship between migraine and RLS, and more speci cally PFO and PAVM.
Right-to-left shunt is more frequent in migraine with aura
Since 1998, several clinic-based case – control studies have been published, indicating a two to three times increased prevalence of RLS in migraine with aura patients compared with controls and migraine without aura patients using transcranial Doppler with aircontrast (TCD-c) [1 – 4,14]. This increased prevalence was also found speci cally for PFO using cardiac echography [4]. A systematic review reported that PFO was more prevalent in migraine with aura patients than in the general population (pooled odds ratio 2.54, 95% con dence interval 2.01 – 3.08) [15]. Recently, two new case – control studies evaluating PFO prevalence were published. In the rst, a population-based sample of mostly non-white participants from the North-
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