Interhemispheric differences of fMRI responses to visual stimuli in patients with side‐fixed migraine aura

Abstract

Migraine sufferers with aura often report photosensitivity and visual discomfort outside of attacks and many consider bright or flickering light an attack-precipitating factor. The nature of this visual hypersensitivity and its relation to the underlying pathophysiology of the migraine aura is unknown. Using fMRI measurements during visual stimulation we examined the visual cortical responsiveness of patients with migraine with aura. We applied a within-patient design by assessing functional interhemispheric differences in patients consistently experiencing visual aura in the same visual hemifield. We recruited 20 patients with frequent side-fixed visual aura attacks (≥90% of auras occurring in the same visual hemifield) and 20 age and sex matched healthy controls and compared the fMRI blood oxygenation level dependent (BOLD) responses to visual stimulation between symptomatic and asymptomatic hemispheres during the interictal phase and between migraine patients and controls. BOLD responses were selectively increased in the symptomatic hemispheres. This was found in the inferior parietal lobule (P = 0.002), the inferior frontal gyrus (P = 0.003), and the superior parietal lobule (P = 0.017). The affected cortical areas comprise a visually driven functional network involved in oculomotor control, guidance of movement, motion perception, visual attention, and visual spatial memory. The patients also had significantly increased response in the same cortical areas when compared to controls (P < 0.05). We discovered a lateralized alteration of a visually driven functional network in patients with side-fixed aura. These findings suggest a hyperexcitability of the visual system in the interictal phase of migraine with visual aura.

No abnormalities of intrinsic brain connectivity in the interictal phase of migraine with aura

“…A better understanding of these mechanisms is crucial for the much-needed improvement of prophylactic treatment. Functional magnetic resonance imaging (fMRI) studies have shown hyperresponsiveness of visual cortical areas in migraine patients with aura interictally [6][7][8]. These symptoms clearly originate from the cerebral cortex [4].…”

Cortical hyperexcitability and sensitivity to discomfort glare

“…Neuronal hyperexcitability has already been implicated in a number of phenomena related to discomfort glare, such as: visual discomfort (Haigh et al, 2013;Juricevic et al, 2010), photophobia (Boulloche et al, 2010;Denuelle et al, 2011) and light-induced migraine (Coutts et al, 2012;Hougaard et al, 2014). For example, using positron emission topography (PET), Boulloche and colleagues (Boulloche et al, 2010) found increased bilateral activity in the visual cortex (specifically the cuneus, lingual gyrus and posterior cingulate cortex) in migraineurs with photophobia at multiple light levels.…”

Migraine: What Imaging Reveals

“…Several studies using visual stimulation BOLD fMRI paradigms have detected hyper-responsiveness in striate areas during visual stimulation in interictal MwA [17,48] as well as more brain activation in the visual functional network including the inferior frontal gyrus and the inferior and superior parietal lobule, all regions involved with attention orienting and oculomotor control (Hougaard and colleagues 2014) [18]. Although results of a smaller study by Bridge et al (2015) [49•] did not find differences in striate cortex activation between MwA and MwoA, the authors demonstrated decreased GABA levels in the occipital cortex and a positive relationship between BOLD-signal change and occipital glutamate/ creatine ratios using magnetic resonance spectroscopy (MRS).…”

“…These studies have implicated common regions that show more activation or hyperactivation between attacks (interictally) in migraineurs relative to healthy controls during sensory processing. These include prefrontal, parietal (postcentral/primary somatosensory gyrus), temporal (temporal pole, fusiform, hippocampus, parahippocampal gyrus) cortex, and subcortical regions (cingulate, thalamic complex) [14][15][16][17][18]. Regions where migraineurs show less interictal activation or hypoactivation relative to healthy controls include areas of the brainstem (pons, medulla) and temporal and parietal (secondary somatosensory) cortex [15,[19][20][21].…”