Objective: To examine the relationship between inflammation and brain atrophy in patients with a clinically isolated syndrome (CIS) suggestive of multiple sclerosis (MS).
Methods: Monthly triple-dose gadolinium (Gd/DTPA)-enhanced MRI scans over 6 months were obtained in 62 consecutive CIS patients with an abnormal baseline MRI scan. Subsequently MRI was performed at months 12 and 18. Patients who developed a clinically definite MS (i. e., a second clinical episode) ended the study at the time of the relapse. For each scan, the number and volume of newly active lesions (Gd-enhancement/new or newly enlarging T2 lesion that did not enhance), and the number and volume of T2 hyperintense lesions (T2-LL) and T1-black holes (T1-LL) were calculated. The percentage of brain volume changes (PBVC) was assessed using a fully automated technique (SIENA; Structural Image Evaluation using Normalization of Atrophy).
Results: Twenty-four (39%) developed clinically definite MS by month 18. Thirty-eight (61%) were relapsefree and completed the MRI follow-up. Relapse-free patients showed a progressive median increase between baseline and month 18 in T1-LL (25%, p<0.001), but not in T2-LL (8.5%, p=ns). PBVC decreased by 1.1% (p<0.001) in a time-dependent pattern (Kendall coefficient of concordance=0.85). Exploratory subgroup analyses showed a trend towards progressive decreases in brain volume in active patients (i. e., those with at least one newly active lesion during monthly MRI scanning; Spearman's R=-0.61; p<0.001), but not among inactive patients (Spearman's R=-0.10; p=0.53). Significant differences in median brain volume changes between the active and inactive patient groups were found at months 12 and 18; the difference detected at month 6 was not significant. The cumulative number and volume of new Gd-enhancing lesions developed during the 6 months of frequent MRI scanning were highly correlated with PBVC over the 18-month period (Spearman R values were 0.73 and 0.85, respectively). The strongest predictor of PBVC at 18 months was the cumulative volume of newly active lesions during frequent MRI scanning [ss=-0. 83, standard error (SE)=0.07, p<0.001].
Conclusions: This study shows that visible inflammation as detected by monthly, triple-dose Gd-enhanced MRI is an important factor in the pathogenesis of brain tissue loss in CIS patients. However, inflammation and brain atrophy do not proceed in parallel: atrophy appeared only after a delay of months following acute inflammation. Frequent MRI scanning allows for the detection of CIS patients who will develop brain atrophy in the short-term.