Small deep white matter lesions are associated with right-to-left shunts in migraineurs

The right-to-left shunts (RLS) and white matter lesions (WMLs) are frequently observed in migraineurs and in patients with ischemic stroke. Previous studies have reported that the burden of WMLs did not increase with the intracardiac right-to-left shunt (RLS) in migraineurs. However, some types of WMLs are known to be associated with RLS in patients with stroke and dementia. The aim of the study was to demonstrate the difference in the size and location of WMLs, according to the existence of RLS in patients with headache. From the prospective headache registry, a total of 425 subjects (age, 30.8 ± 5.1 years; 303 women; 242 migraineurs; 183 patients with tension-type headache (TTH)) were retrospectively reviewed and evaluated for RLS and WMLs using M-mode power transcranial Doppler sonography (mTCD) and brain magnetic resonance imaging scans. We scored WMLs, according to the Rotterdam Scan Study, and assessed the association between RLS presence and the location and size of WMLs. The number of small deep WMLs (dWMLs) and the prevalence of RLS, defined as microembolic signals (MES) ≥ 11, were higher in patients with migraine (small dWMLs, 6.23 vs. 4.05; RLS, 36.8% vs. 10.9%), compared to patients with TTH. There was no significant difference in the sum of periventricular WML grades or the total volume of dWMLs between TTH and migraine patients. Among the migraineurs, the patients with RLS more frequently had small dWMLs, aura, and heart disease compared to those without RLS. In addition, RLS were also independent predictors for the presence of small dWMLs from the multivariate binary regression analysis (p < 0.01; OR = 3.24; 95%CI 1.56-6.72). Small dWMLs are associated with RLS in young migraineurs. These results imply that paradoxical embolism may cause the small WMLs in some migraineurs.