The way they usually tell that a lesion is older than otherss is with contrast. After the initial images are taken, a contrast agent is injected. If a lesion is active, or has been active in the last 30-40 days, it will enhance in the presence of the contrast agent. Basically it will "light up".
If you have some lesions that enhance and someeee that don't you satisfy the dissemination in time component of the McDonald criteria.
hi there, i didn't ask my question very well although your answer was still very helpful. What I am wondering is what does it mean that one is older and one is newer?? Can they tell how old they are?
They can't tell how long a lesion has been there but they can tell if one is "new", meaning it "lights up" as Kyle mentioned above.
If a lesion is "old" it doesn't "light up" with contrast when an MRI is performed. There is no way to tell how old a "old" lesion is unless you are comparing a previous MRI that didn't show the lesion initially.
When I was diagnosed, I had two "old" lesions and one "new" one. I am assuming (maybe wrongly) that my two old lesions corresponded with my two previous relapses and my third relapse was currently caused by the "new" lesion since when the MRI was performed I was still experiencing MS symptoms.
Lesions can form however and you may not experience any "symptoms".
It just menas that MS has been active at different times. If some lesions enhance and ohers do not, it means that MS is active now and was active at least 30-40 days ago.
As Julie mentioned, it is also possible to guage frequency of MS activity using MRI without contrast. If you have an MRI today it may show 3 lesions, 6 months from now you have a second MRI and it shows 5 lesions. You can determine that you MS was active at some point prior to the first MRI and also at some point between the first and second MRIs.
It's just about impossible to tell how long the lesions from the first MRI have been there if none of them enhance.
Also, some people with MS have hundreds of lesions, some just a few. Just b/c you have three lesions, doesn't mean that you have had three different sets of relapses or that you have fewer symptoms than someone with 30 lesions.
The number of lesions isn't as important as location. The way it was initially described to me is that it's like shooting into a wall with electrical wires. If the shots miss the wires then there are few if any symptoms. If they hit a wire though which controls something important, it can cause major problems.
Thank ya'll so much, just trying to understand it all.
There's a lot of info to digest, MS-wise speakin' :-)
One reource that helped me was MS for Dummies. It does actually exist, and translates a lot of medspeak into human speak.