Quantitative Measurement of tissue damage and recovery within new T2w lesions in pediatric- and adult-onset multiple sclerosis

Background: Children and adolescents with relapsingremitting multiple sclerosis (RRMS) have a similar T2 lesion burden as adults matched for disease duration. However, it is unknown whether the degree of tissue destruction within lesions is also similar. Persistent reduced T1-weighted signal intensity within lesions indicates loss of tissue integrity. Objective: We aimed to compare change over a 2-year period in T1 intensity within new T2 lesions, from pre-lesion levels to chronic post-lesion levels, between pediatric and adult-onset MS. Methods: A two-point intensity-normalization method was used to generate normalized T1-weighted (NT1) images from T1-weighted data in 29 pediatric MS patients (age(mean±SD, years), disease duration (years)=15.7±2.4, 3.9±2.6) and 24 adult MS patients (36.7±8.9, 6.9±4.8). Subjects were imaged at three consecutive timepoints, 1 year apart. For each subject, a new-T2 lesion mask was created and the NT1 intensities pre-lesion, peri-lesion and post-lesion were determined. A longitudinal model was used to capture NT1 changes. Results: The NT1 in both groups failed to recover to pre-lesion values by 1 year post-lesion (p=0.0002), with children showing significantly better recovery than adults (p=0.0089). Conclusions: Both groups showed a significant chronic reduction of T1 intensity within new T2 lesions. However, children showed a significantly greater recovery of T1 intensity, suggesting that MS lesions in the pediatric MS population are less destructive, or that pediatric patients have greater reparative capacity.