The deep cervical lymph nodes (dCLNs) are sites of immune presentation and B-cell maturation from the brain, and potentially involved in mechanisms of neuroinflammation. We hypothesized a reduction in dCLN volume following B-cell depletion therapy. In a retrospective cohort, we segmented bilateral dCLN from T2-FLAIR MRI at "prebaseline," "baseline," and "post-B-cell depletion" timepoints. Using a multivariable mixed-effect regression model, we find no changes in dCLN volumes between prebaseline and baseline timepoints ( > 0.05), but a significant decrease of 158 mm following ocrelizumab infusion ( = -3.3,  = 0.005). Baseline use of a disease-modifying therapy was also significantly associated with a smaller dCLN volume and attenuated the effects of B-cell depletion. These results are congruent with therapeutic mechanisms, although other alternative explanations for reductions in dCLN volumes cannot be ruled out based on this data. Deep CLN represent potential imaging biomarkers of pharmacological or clinical utility and warrant further investigation.