I just thought I'd do a smell test. Google Scholar: mri brain lesions -ms
There are a lot of hits. So I think you have a point. Here is a good one:
Brain lesions in alcoholics
If having a few ... ok, a lot of beers can give you lesions ....... well?
I say this tongue in cheek somewhat. But, then, you read something like this ....Incidental Brain Lesions on Magnetic Resonance Imaging and Neurobehavioral Functions in the Apparently Healthy Elderly
Looks like someone has thought about this. I'm not going to beat this up. Looks like there are lots of reasons folks might have lesions and perhaps ordinary folks or crazy ones like me.
But to change my directionless thinking,
Lyon, WAY more folks host long term bacterial infection. Lots and Lots of folks are carrying the bacteria that causes pneumonia and don't know it. But, it's a smaller number (if you accept the CPn thinking on this) of folks who get this bacteria through the obstacle course that gets it into the CNS. We know it gets out of the lungs, just ask the cardiology folks, and we know it can live in your body for decades.
So I'm just trying to tie back to your thinking - this idea works and is tangentially explanatory of how billions are exposed to pneumonia and a fraction of those get MS. I bet if most of us had the test for pneumonia anti-bodies, we'd be surprised at the results. Ken