SLC1A2 and secondary progressive multiple sclerosis: Non-parametric Kruskal–Wallis test revealed statistically significant differences (p < 0.001) among the four groups and the Mann–Whitney U test showed a statistically significant increase in the percentage of plasma EV-EAAT2 in relapsing RRMS patients compared to remitting RRMS patients, SPMS patients and healthy controls (Fig. 6A).