Assessment of Cerebral Perfusion Asymmetry in Chronic Migraine Patients Using Intravoxel Incoherent Motion...

Chronic migraine (CM) is associated with neurobiological alterations beyond episodic attacks, yet cerebral microvascular perfusion changes during the interictal phase of CM remain underexplored. Intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) provides diffusion-derived pseudoperfusion parameters that reflect regional microvascular alterations in the brain parenchyma. Accordingly, this study aimed to investigate right-to-left hemispheric asymmetry of IVIM-derived perfusion parameters in migraine-implicated cortical and subcortical regions during the interictal phase of CM. Thirty patients with CM imaged during the interictal phase, along with 30 age- and sex-matched healthy controls, underwent IVIM imaging. IVIM parameters, including the pseudodiffusion coefficient (D*), perfusion fraction (f), and their composite metric (fD*), were estimated using a Bayesian probability-based fitting algorithm. Region-of-interest (ROI) analysis was performed bilaterally in migraine-implicated cortical and subcortical regions. Hemispheric asymmetry indices (HAIs) of IVIM parameters were calculated and compared between groups using Benjamini-Hochberg (FDR) false discovery rate correction. No absolute IVIM parameter showed significant interhemispheric differences in either group after FDR correction. In addition, no significant group differences in HAI of IVIM parameters were identified across the six cortical regions or pontine tegmentum. In contrast, posterior thalamic fD* asymmetry was significantly greater in patients with CM than in controls (median HAI: 27.91 vs. 10.43; p = 0.002, q = 0.017). Exploratory analysis confirmed greater separation between bilateral posterior thalamic fD* measurements in CM versus control subjects (0.429 vs. 0.151 × 10^-3 mm²/s; p = 0.002), whereas leave-one-out analysis showed that this outcome was not driven by any single participant. Interobserver agreement for HAI measurements was good for D* (ICC = 0.81) and moderate for f and fD* (ICC = 0.70 and 0.69, respectively). These findings indicate that CM is associated with increased hemispheric asymmetry of IVIM-derived microvascular perfusion in the posterior thalamus during interictal phase, suggesting lateralized thalamic microvascular alterations in CM.