Recurrent depressive disorder (RDD) and bipolar disorder (BD) are the most common affective disorders worldwide. However, the pathogenesis of these disorders remains far from understood. Macromolecular proton fraction (MPF) mapping is a sensitive and specific quantitative MRI method for the assessment of brain tissue myelination, but its clinical value for affective disorders remains unknown. This cross-sectional study employed fast MPF mapping on a 1.5 T MRI scanner using the single-point synthetic reference method to investigate myelin abnormalities in white matter of RDD and BD patients. ANOVA revealed a significant main effect of the group (RDD vs. BD vs. two age-matched control groups; F (3.76) = 7.42, p < 0.001, η² = 0.227). MPF values were significantly reduced in RDD versus BD patients (p < 0.001). BD showed elevated MPF compared to controls (p = 0.01). MPF levels showed significant weak-to-moderate correlations with clinical scales of affective disorders. These findings demonstrate divergent cerebral myelination patterns—hypomyelination in RDD versus an increased myelin content in BD. In conclusion, MPF mapping demonstrated a promise as a marker of myelin content changes in affective disorder.

. This study aimed to test the method of fast molecular proton fraction mapping as a tool for quantitative assessment of myelin deficiency in affective disorders between general and local measurements in seven selected regions of interest of both hemispheres in comparison with the control group, determining the sensitivity and specificity of the method. Materials and methods . The study included 24 patients with affective disorders, 13 were diagnosed with a current depressive episode as part of recurrent depressive disorder, and 11 were diagnosed with bipolar affective disorder. All patients underwent non-contrast magnetic resonance imaging of the brain using a fast MPF mapping protocol. Comparison of the MPF levels for the control and experimental groups were calculated using the Mann-Whitney U-test. ROC analysis was used to assess the prognostic value of the investigating parameters. Results . The average MPF indices of all selected regions of interest for the control group and group of patients with affective disorders (AD) were significantly different (p < 0.0001). In a pairwise comparison of each selected area, patients with AD showed a significant decrease in MPF in all selected areas of white matter compared to the control group (p < 0.05). Analyzing the ROC curves, the largest areas under the ROC curves (AUC) were 0.892 ± 0.061 (83.3%; 88.89%) and 0.888 ± 0.054 (70.83%; 83.3%) in the periventricular zone and thalamic area respectively. which indicates the “high” information content of these models for detecting the process of hypomyelination in patients with AR. Conclusion . Affective disorders are characterized by a significant decrease in the MPF of the white matter of the brain in comparison with the control group (p < 0.05), which indicates a decrease in the concentration of myelin in the observed areas. The process of hypomyelination is diffuse as it was significantly expressed in all selected regions of interest in patients with affective disorders, including the periventricular zone and the area of thalamus and basal ganglia in comparison with controls (p < 0.05). MPF changes in the periventricular zone have the greatest diagnostic value for detecting hypomyelination in AD (PPV = 91%, NPV = 80%).

Recurrent depressive disorder (RDD) and bipolar disorder (BD) are the most common affective disorders worldwide. However, the pathogenesis of these disorders remains far from understood. Macromolecular proton fraction (MPF) mapping is a sensitive and specific quantitative MRI method for the assessment of brain tissue myelination, but its clinical value for affective disorders remains unknown. This cross-sectional study employed fast MPF mapping on a 1.5T MRI scanner using single-point synthetic reference method to investigate myelin abnormalities in white matter of RDD and BD patients. ANOVA revealed a significant main effect of the group (RDD vs. BD vs. 2 age-matched control groups; F (3.76) =7.42, p<0.001, η²=0.227). MPF values were significantly reduced in RDD versus BD patients (p<0.001). BD showed elevated MPF compared to controls (p=0.01). MPF levels showed significant weak-to-moderate correlations with clinical scales of affective disorders. These findings demonstrate divergent cerebral myelination patterns—hypomyelination in RDDversus an increased myelin content in BD. In conclusion, MPF mapping demonstrated a promise as a marker of myelin content changes in affective disorder.