Disrupted functional connectivity in the hippocampal subregions of patients with migraine without aura: a functional study on mechanisms underlying migraine chronification

Background Despite increasing evidence indicating hippocampal dysfunction in migraineurs, they overlooked the functional differences among hippocampal subregions and mostly used static functional connectivity (sFC). This study aimed to combine sFC and dynamic functional connectivity (dFC) to investigate the role of hippocampal subregional functional changes in migraine chronification. Methods Resting-state functional MRI scans were performed on 52 patients with episodic migraine (EM), 22 patients with chronic migraine (CM), and 67 healthy controls (HCs). The bilateral rostral hippocampus (rHipp) and caudal hippocampus were selected as regions of interest. Differences in sFC and dFC values between the hippocampal subregions and other brain regions among the three groups were compared through the analysis of the general linear model. Spearman partial correlation analyses were used to assess the relationship between FC and clinical parameters in the migraine cohort. Results In the sFC analysis, both EMs and CMs showed reduced connectivity between the left rHipp and the left orbital part of medial frontal gyrus as compared with HCs. In the dFC analysis, both the CM and EM groups exhibited increased connectivity between the right rHipp and the right calcarine compared to HCs, and the CM group demonstrated decreased dFC between the aforementioned brain regions relative to the EM group. No significant correlations were found between sFC and dFC values and clinical characteristics in patients with EM and CM. Conclusion Altered sFC and dFC between the rHipp and the orbital part of medial frontal gyrus and calcarine in CM patients may be associated with dysfunctions in emotion, cognition, and multisensory integration, providing new insights into mechanisms of migraine chronification.