can an mri alone diagnose ms?

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i have had 3 episodes of optic neuritis, once in june 2006, once whilst pregnant in february 2007 and again 4 months after giving birth in november 2007, since then i have had numbness and tingling all over my body excluding my torso for 2 weeks then on another occasion i have had the right side of my body just do as it pleases, if i tried to touch my finger on my nose for example it would get nowhere near, and with my leg and foot i would actually have to look at it to make sure it was doing what i thought it was doing. i am have my second mri scan this weekend and wondered if this is likely to give a diagnosis or not. my neurologist thinks it is either the onset of ms or a complicated migraine - from what i read there is a big difference betweeen the two
any advice much appreciated