Cortical excitability changes in chronic migraine vs episodic migraine: evidence by sound-induced flash illusions

Introduction: Sound-induced flash illusions(SIFI) permit to evaluate crossmodalaudio-visual perception. When one flash is accompanied by twobeeps, it is perceived as two flashes(’fission’illusion); a ‘fusion’ illusionoccurs when a single beep causes the fusion of a double flash stimulus.SIFI strictly depends on cortical excitability: healthy controls perceive lessillusions by increasing visual cortex excitability through anodal tDCS [1].Aim: to evaluate if, due to cortical hyperexcitability, differences in SIFIoccur in migraine and further changes can be found across migrainecycle, migraine chronification an drug overuse.Methods: we enrolled 64 patients with episodic migraine, 32 with-(MWA)and 32 without-aura(MWO) (42 F, mean age 32,3±16yrs), 44 patients withchronic migraine with medication overuse headache (36 F, mean age 39.2±12.2), and 20 healthy controls (13 F, mean age 38±18). All underwent aparadigm for SIFI induction where had to report the number of flashesseen. 13 of MWO and 12 out of MWA were examined in both ictal andinterictal phaseResults: all migraine groups showed significantly less SIFI than controls(p<.0001); illusions are more reduced in in chronic migraine andparticularly in those overusing triptans(p<.05).Conclusions: results point to a condition of visual cortical hyperresponsivityin patients with chronic migraine in analogy to what observed in episodicpatients expecially during ictal phase. This is in agreement with the view ofchronic migraine as a ‘never ending attack’. The greater effect showed intriptan overuser can follow to down-regulation of 5HT1 receptors.No conflict of interest.Reference1. Bolognini N, et al: Neuropsychologia 2011, 49:231-7.