McDonald criteria?

Am I right in thinking that an MRI must show at least one lesion before a Dx of MS can be given? I have had 3 relapses in the last 12 months, but my brain and cervical spine MRI was clear. Seeing Neuro again next week and from what he said last time, next step will be a LP, but is there any point in having it yet? Gp has talked of annual MRI’s, so am I right in thinking that, even if Nuero exam and LP point to MS a Dx will not be given until I have had a positive MRi? Have spoken to people at my local MS group and many of them can’t get there heads round this as they got a Dx before MRi’s were routine.

Aha! This is just the type of question our Rizzo can help with. i`ll be watching for her reply.

luv Pollx

The McDonald criteria state that you need to have at least one lesion in at least two places typical of MS (juxtacortical, periventricular, infratentorial, spinal cord). So the smallest number of lesions is two and they have to be in the right places.


It is possible to be diagnosed with MS with a clear MRI. There are all sorts of reasons for this, but the upshot is that some people with MS do not have lesions that are visible on MRI. The neuro would have to be completely confident that there is no other cause of your symptoms though and your history and clinical exam would have to be consistent with MS.

The best place to read about the McDonald criteria is the actual paper that stipulates them. Just google Polman et al (2011). Diagnostic Criteria for Multiple Sclerosis: 2010 Revisions to the McDonald Criteria. ANN NEUROL 2011;69:292–302. I can try and help with any questions about it.

Karen x

Sorry, I should have said that a positive LP would support a diagnosis of MS, but it is not a definitive test - anything up to 20% of people with clinically definite MS have a negative LP and it is possible to have a positive LP but not have MS.

If I were you, I would have an LP. It’s another piece of the puzzle and may provide some important info. I think, however, that I would ask the neuro exactly what would happen if your LP was positive / negative, so you can make an informed decision.

I would also push for better quality MRI if you have only had the standard NHS scans to date and the neuro is sitting on the fence. Ideally a 3T scanner with 3mm slices - your neuro should know what this means!

And what about a thoracic scan? If your symptoms involve anywhere from the chest down, you should have a thoracic scan.