Gray Matter Pathology in MS: A 3-Year Longitudinal Study in a Pediatric Population

BACKGROUND AND PURPOSE: GM pathology is considered a major determinant of disability in MS, but the comprehension of its origin and progression rate is limited by the uncertainty of dating the biologic disease onset. Thus, we planned a longitudinal study aimed at analyzing and comparing cortical pathology in pediatric and adult MS patients at clinical onset. MATERIALS AND METHODS: Within 12 months from clinical onset, 35 patients with cMS and 57 with aMS were included in a longitudinal study. At T0, GMf and CL number and volume were analyzed. Percentages of Delta-GMf and number of new CLs were assessed every year for 3 years (T1-T3). Twenty-eight age- and sex-matched NCs constituted the reference population. RESULTS: At TO, GMf did not differ between cMS and NC (P = .18), while it was lower in patients with aMS compared with both NCs (P < .001) and patients with cMS (P < .001). The number of patients with CLs, as well as CL number and volume, were higher in patients with aMS than in those with cMS (P < .001). At T3, Delta-GMf was higher in both patients with cMS (1.6% +/- 0.5%; range 0.7%-3.4%; P < .001) and aMS (1.6% +/- 0.6%; range 0.6%-3.4%; P < .001) compared with NCs (0.7% +/- 0.2%; range 0.4%-1.1%), whereas no difference was observed between patients with cMS and aMS (P = .93). Delta-GMf significantly correlated with increased CL volume (cMS: r = 0.46; aMS: r = 0.48) and with the appearance of new CLs (cMS: r = 0.51; aMS: r = 0.49). CONCLUSIONS: Our findings suggest that focal (CLs) and diffuse (atrophy) GM damage are strictly associated with the biologic onset of MS, and proceed linearly and partly independently of WM pathology.