Microstructural changes precede depression in patients with relapsing-remitting Multiple Sclerosis

Background Multiple Sclerosis lesions in the brain and spinal cord can lead to different symptoms, including cognitive and mood changes. In this study we explore the temporal relationship between early microstructural changes in subcortical volumes and cognitive and emotional function in a longitudinal cohort study of patients with relapsing-remitting Multiple Sclerosis. Methods In vivo imaging in forty-six patients with relapsing-remitting Multiple Sclerosis was performed annually over 3 years magnetic resonance imaging. Microstructural changes were estimated in subcortical structures using the free water fraction, a diffusion-based MRI metric. In parallel, patients were assessed with the Hospital Anxiety and Depression Scale amongst other tests. Predictive structural equation modeling was set up to further explore the relationship between imaging and the assessment scores. In a general linear model analysis, the cohort was split into patients with higher and lower depression scores. Results Nearly all subcortical diffusion microstructure estimates at the baseline visit correlate with the depression score at the 2 years follow-up. The predictive nature of baseline free water estimates and depression subscores after 2 years are confirmed in the predictive structural equation modeling analysis with the thalamus showing the greatest effect size. The general linear model analysis shows patterns of MRI free water differences in the thalamus and amygdala/hippocampus area between participants with high and low depression score. Conclusions Our data suggests a relationship between higher levels of free-water in the subcortical structures in an early stage of Multiple Sclerosis and depression symptoms at a later stage of the disease. Plain language summary Signals between the brain and spinal cord are disrupted in people with Multiple Sclerosis. For those with relapsing-remitting Multiple Sclerosis (RRMS), symptoms get periodically better and worse over time. We looked at whether changes in the brain of people with RRMS were associated with changes in their mood over time. People who had more changes in certain areas of the brain at the start of the study were more likely to have symptoms of depression later. This work suggests that early changes in the brain may be linked to increased symptoms of depression over time in people with RRMS. We believe this could be an opportunity to provide care to those suffering from RRMS to lessen the impact of severe depression