Demyelination and white matter injury in MS
This study looked at the changes that occur in the brains of people during the different stages of MS. The researchers used brain tissue taken from 52 people with MS. 11 people had a very rare acute form of MS called Marburg’s where disease progression was sudden and severe leading to death within months after onset. Six had relapsing remitting, 15 primary progressive, 20 secondary progressive and 15 without any known disease as a comparison.
The samples were investigated for the following aspects:
- areas of inflammation where immune (white blood) cells have entered the brain and damaged the protective outer casing (myelin) of nerve fibres to form a lesion or scar,
- demyelination, where myelin is damaged or destroyed,
- axonal damage (damage to the long extensions of nerve cells which allows cells to talk to each),
- diffuse white matter injury (damage to large areas of the brain that contain large amounts of myelin).
Results showed that acute MS had the highest number of ‘active lesions’ where large numbers of white blood cells were still entering into the brain to form localised areas of damage. Fewer lesions were seen in relapsing remitting type than in acute MS. Low numbers of “active lesions” were found in people with progressive MS.
In contrast, the progressive forms of the disease were characterised by more demyelination and axonal damage compared to the other types of MS. Higher levels of demyelinated areas and inflammation throughout the brain were found in secondary progressive disease compared to primary progressive. The level of widespead damage within the brain was found to be independent of the number of lesions seen.
This study reports that MS starts as a local inflammatory disease of the brain with localised demyelinated lesions. As the disease progresses, inflammation appears to become more widespread throughout the whole brain, causing further demyelination and damage to axons.
This report was published in Brain, volume 129 part 11, November 2005.
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