The hypothalamus may mediate migraine and ictal photophobia: evidence from Granger causality analysis

The hypothalamus plays a central role in the pathophysiology of migraine and is considered to be the "migraine generator." It participates in initiating a migraine attack through its connectivity to regions of the brain involved in processing and modulating pain. However, the underlying mechanisms of hypothalamic effective functional connectivity that bring about migraines remain unclear. This study investigated the hypothalamus-based directional effective connectivity in migraine without aura patients and assessed associations among the clinical characteristics.

Seven patients with migraine without aura during the attack (MWoA-DA) (four with photophobia (MWoA-DAWP) and three without photophobia (MWoA-DAWoP)), twenty-seven patients with migraine without aura during the interictal period (MWoA-DI), and twenty-nine healthy controls (HC) were included in this study. Granger causality analysis (GCA) was used to investigate the directional effective connectivity between the hypothalamus and other brain regions.

MWoA-DA patients exhibited decreased outflow from the bilateral hypothalamus to the visual cortex compared with the MWoA-DI patients and HCs. The MWoA-DAWP group primarily contributed to this result. The MWoA-DA patients showed decreased outflow from the bilateral hypothalamus to the right inferior parietal gyrus compared with the HCs. The visual analogue scale (VAS) was negatively correlated with abnormal effective functional connectivity from the right hypothalamus to the right inferior parietal gyrus in the MWoA-DA group.

These data provide evidence that the hypothalamus might serve as a central component of a multisystem network implicated in migraine and ictal photophobia, which includes hypothalamus and the visual and trigeminovascular systems.