Originally posted by jumpinjiminy
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It’s true that lesions can heal and disappear and be small enough to fall between MRI slices. But in active disease, where new lesions are forming, the laws of probability (and randomness) dictate that they won’t always occur between slices. Eventually -- like a coin toss -- some of those lesions -- by chance alone -- are going to show up in a slice. At some point it becomes more suspicious if they don’t.
That 5% rate of diagnosis without MRI findings isn’t proof of MS. It’s an assumption made in the absence of evidence that the condition is anything else. Plus, it's usually made in the presence of other supporting information, such as a positive LP and/or abnormal VEP. I don't know what percentage of people have been diagnosed with MS who have no imaging or lab findings to back it up, but it has to be notably less than 5%.
It’s also true that the MRI machines in common aren't particularly sensitive to changes in gray matter. But MS doesn’t primarily affect gray matter. (The estimated ratio of white matter lesions to gray is 95:5). Myelin covers cell axons (white matter) not cell bodies (gray matter). The primary action of MS is to demyelinate axons. It isn’t reasonable to think that the damage (inflammatory or otherwise) in your brain is from MS but it’s in gray matter and just not showing up on MRI. It's also debatable whether there can be damage and symptoms affecting large areas of the body but all of the damage is microscopic.
The 7T units haven't moved into widespread use yet because research hasn't shown there to be a major clinical/diagnostic advantage to using them. Even though they're picking up smaller lesions that the less-powerful units don't, diagnosing, say, 2% of MS cases earlier hasn't yet proved to be enough of an advantage to justify the cost or overcome some of the drawbacks of the technology.
Another reason brain lesions are important in your case is that something needs to explain the long-lasting episodes of blurry vision. Every structure involved with vision and visual processing is contained inside the head. It isn’t reasonable to think that demyelination from MS is making your vision blurry on multiple occasions and for long periods of time yet leaving no evidence in your brain. It's also questionable that MS would cause long-lasting inflammation in your brain on multiple occasions but never cause demyelination. The lack of physical evidence of MS indicates that the cause probably isn't MS. It makes more sense that whatever’s causing the visual problems is something occurring inside the brain that doesn’t have the same modus operandi as MS.
It also isn’t reasonable to think that MS is responsible for your blurry vision, yet all of the physical clues are going to be found outside your brain. The cause of your visual problems isn’t in your thoracic spinal cord.
That comes back to the 5% who have been diagnosed with MS with clean MRIs -- or maybe the couple of percent who have been diagnosed with no specific objective evidence at all. Can someone have purple creeping crud if what they have isn't purple, creeping or cruddy? Can a person have multiple sclerosis if they don't have multiple scleroses?
The revising panel for the McDonald diagnostic criteria aimed to eliminate the confusion about MS being diagnosed with questionable findings. The 2010 McDonald criteria closed the door to MS being diagnosed without MRI evidence of dissemination in time and space. There will be no more "confusing everyone" by saying it can be determined without an MRI. So it remains to be seen how many people will be diagnosed in the future with clean MRIs. But it's clear that those people will be diagnosed at the discretion of the doctors, outside the scope of the McDonald criteria.
If they choose to either edit or not approve my posts so be it. However, since I am expressing my opinions in a civil way and not getting personal, as well as discussing facts, I think my posts are ok. You may choose to add me to your ignore list so you don't have to see me.
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