Smouldering inflammation detectable even in the earliest stages of MS

It may be that chronic lesion-associated smouldering inflammation is more pronounced in the later phase of the disease, but it can be detected from the earliest stages of MS, according to Finnish research. The prevalence of paramagnetic lesions (PRLs) was highest in patients with the shortest disease duration.

A Finnish study evaluated the presence of smouldering inflammation associated with chronic lesions throughout the various stages of MS. Dr Markus Matilainen (University of Turku, Finland) and colleagues used concurrent MRI and PET imaging with a [¹¹C]PK11195 radioligand, binding to 18 kDa translocator protein (TSPO), which is increased in activated microglia. Quantitative susceptibility mapping MRI was used to detect PRLs.

A total of 127 patients underwent concurrent MRI and PET. Of these, 91 patients had relapsing-remitting MS and 36 had progressive MS; mean age was 45 years and median disease duration was 9.2 years. T1 lesion load and number of T1 lesions correlated with disease duration. Newly diagnosed patients and patients with the longest disease duration (>20 years) had the highest amount of PRLs. Microglial activation in the normal-appearing white matter correlated with disease duration, disability, and age. The proportion of rim lesions with active microglia correlated with disease duration.

Dr Matilainen noted that the proportion of patients with no active rim lesions was lowest in the longest disease duration group, but the proportion of patients with ≥7 active rim lesions was highest in that same group.

Dr Matilainen concluded that lesions with high TSPO PET-detectable microglial activity at the rim were more prevalent in late stages of the disease, while prevalence of PRLs was also high among patients with the shortest disease duration. Therefore, the main takeaway message, according to Dr Matilainen, is that smouldering inflammation is already present in the earliest stages of MS.

1. Matilainen M, et al. Evolution of smouldering inflammation throughout MS disease course. O027, MSMilan 2023, 11–13 October, Milan, Italy.

 

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Posted on 4 December, 2023