Abstract Details

The dominant lesion type in progressive multiple sclerosis is a chronic lesion, and particularly chronic active lesions harboring a lesion border of activated microglia and macrophage cells have been associated with lesion growth and disability accumulation.

To investigate whether the frequency of TSPO-PET-identifiable chronic active lesions predicts later multiple sclerosis disease progression.

The innate immune cell activation was evaluated at baseline using PET-imaging with a TSPO-binding radioligand ¹¹C-PK11195 in 82 multiple sclerosis patients. Conventional MRI and disability measurements using the Expanded Disability Status Scale were performed for patients at baseline and 5.0±1.7 years later (mean±SD). Chronic lesions were categorized into three categories: rim-active, inactive and overall-active, based on their PET-detectable innate immune cell activation patterns in the lesion core and in the 2-mm perilesional rim. Progressed and non-progressed patients were first compared using Wilcoxon rank-sum test and finally forward-type stepwise logistic regression was used to find the most important predictors of progression.

Twenty-one (26%) patients experienced disability progression during the follow-up. These patients had significantly higher absolute and volume proportions of rim-active lesions (P < 0.001 in both) and significantly lower absolute and volume proportions of inactive lesions (P < 0.001 and P = 0.007, respectively) compared to non-progressed patients. The results were similar in the patient group free of relapses (n = 60). In logistic regression the model with categorized variable ‘patients with proportion of rim-active lesions > 10% and proportion of inactive lesions ≤ 50% vs. others’, predicted disease progression both in the entire patient cohort (OR = 26.8, p < 0.001) and in the patient group free of relapses (OR = 34.8, p = 0.002).