SUBCORTICAL VOLUMETRIC CHANGES ASSOCIATED WITH MIGRAINE CHRONIFICATION: A COMPARATIVE STUDY OF EPISODIC AND CHRONIC MIGRAINE

Migraine chronification is a significant clinical issue and may indicate long-term neuroplastic changes in subcortical pain processing and modulatory networks. We aimed to identify volumetric differences in subcortical and brainstem structures between episodic and chronic migraine by normalizing volumes to intracranial volume using automated MRI volumetry. Structural T1-weighted brain MRI scans were obtained from migraine patients classified as either episodic (n=8) or chronic (n=5). Automated segmentation and volumetric quantification were performed using volBrain. Relative volumes normalised to intracranial volume (%ICV) were extracted for the brainstem, thalamus, putamen, and caudate nucleus. Volumes of the amygdala and hippocampus were also assessed as limbic pain modulatory structures. Group comparisons were conducted using two-tailed Mann-Whitney U tests. ICV-normalised volumetric comparisons revealed an increasing trend in relative thalamic volume in chronic migraine compared to episodic migraine (median[IQR]:1.04 [0.80] vs 0.83 [0.23]; U=7.0, Z=−1.91, p=0.056), indicating a moderate-to-large effect size (r=0.53). No significant differences were observed for relative volumes of the brainstem, putamen, amygdala, hippocampus (p=0.770, 0.341, 0.497, 0.213). Despite a non-significant group difference, caudate relative volume showed a moderate effect size (U=9.0, p=0.107; r=0.45). Patients with chronic migraine demonstrated higher mean relative volumes in thalamic, striatal, and limbic structures than patients with episodic migraine. However, brainstem volume did not consistently increase. ICV-normalised subcortical volumetry suggests that thalamic structural variability may be associated with migraine chronification. The descriptive pattern of higher relative subcortical volumes in chronic migraine patients supports the possibility of neuroplastic changes in pain-related networks during the progression from episodic to chronic migraine.