White matter alterations in episodic migraine without aura patients assessed with diffusion MRI: effect of free water correction

Objective To assess the efect of modeling free water (FW) on the identifcation of white matter (WM) microstructure alterations using difusion Magnetic Resonance Imaging (dMRI) in episodic migraine without aura patients compared with healthy controls. Background Difusion tensor imaging (DTI) studies examining WM in migraine patients previously overlooked the potential infuence of FW partial volume efects. Correcting FW efects could ofer a clearer understanding of WM changes in migraine. This study is the frst to incorporate FW efects when evaluating alterations in WM tracts in migraine patients, ofering a comparison to standard DTI analysis. Methods A group of 14 patients with low-frequency episodic menstrual-related migraine without aura and 15 healthy controls matched for the phase of the menstrual cycle were recruited and underwent dMRI acquisitions. FW partial volume fraction was estimated, the difusion signal corrected and the difusion parameters calculated from both FW-corrected and uncorrected signals. Tract-Based Spatial Statistics (TBSS) and WM skeleton regions of interest (ROI) analyses were used to compare between groups. Results Comparisons between control subjects and migraine patients with TBSS and ROI analyses revealed signifcantly lower axial difusivity (AD), both with and without FW correction, as well as altered FW values in migraine patients in some WM tracts. TBSS detected MD changes only after FW correction. Conclusions These fndings suggest WM alterations in these migraine patients in comparison with control subjects, in accordance with other migraine studies. Diferences in the difusion parameters might point to infammatory processes in migraine related to cellular swelling.