Ocrelizumab-Induced Brain Volume Dynamics in Relapsing-Remitting Multiple Sclerosis

Area of Science:

• Neurology
• Neuroimaging

Background:

• Ocrelizumab effectively reduces inflammation in relapsing-remitting multiple sclerosis (RRMS).
• Brain volume changes, including white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF) contributions to atrophy and pseudoatrophy, require further characterization during ocrelizumab treatment.

Purpose of the Study:

• To analyze longitudinal brain compartment dynamics in RRMS patients treated with ocrelizumab.
• To identify clinical and time-dependent predictors of ocrelizumab-induced brain volume changes.

Main Methods:

• A four-year prospective study of 51 RRMS patients.
• Evaluation of WM, GM, CSF, and total brain volume (TBV) at absolute time points and infusion intervals.
• Correlation analysis with Expanded Disability Status Scale (EDSS), age, age at onset, and disease duration (DD).

Main Results:

• Significant increases in ventricular CSF (vCSF) and CSF; significant decreases in WM, WM fraction (WMF), TBV, and brain parenchymal fraction (BPF).
• Transient, non-linear changes in the first year suggest pseudoatrophy (inflammation resolution) rather than irreversible tissue loss.
• Higher EDSS, older age, later age at onset, and longer DD correlated with reduced GM, peripheral GM (pGRAY), and TBV.

Conclusions:

• Ocrelizumab-induced pseudoatrophy is primarily WM-driven and age-dependent.
• WM shrinkage contributes most to parenchymal loss, leading to secondary CSF space widening.
• Age is a critical predictor of brain atrophy and neurological impairment in RRMS patients undergoing ocrelizumab therapy.