There are many diseases that mimic MS, including Lupus, Lyme disease, B12 deficiency, etc. MS is a often dx of "exclusion", whereby it is often diagnosed only once all other conditions have been ruled out.

"Lesion" basically means any kind of damage. Within the brain, lesions (damage) may be caused by many conditions, i.e. migraines or strokes.

With MS, what they are looking for is a certain type of lesion; correct size, shape, and location, either on the brain, or spinal cord. If the right kind of lesions are visible on an MRI, this is one indication that we have MS. However, lesions are not the be-all/end-all as far as diagnosing MS, or monitoring disease progression. Our history is equally important.

MRI's are just one tool used in the dx, but the results of this test (or a spinal tap), are not 100% reliable either. That is why Neuro's first eliminate all other conditions and factor in additional testing results - clinical testing, Evoked Potentials, patient history, etc. - into the dx process.

If the lesions are not enhanced, it is sometimes because dye was not with the MRI. If it was used (and they are MS lesions), it is likely that the unenhanced lesions are plaque (scar tissue) which is not currently inflammed.

It may be that the lesions do not "appear" to be MS lesions, or they are in a different area of the brain then where ours are typically found. Then, with the lesions not currently enhancing (or perhaps because there was little change from the last MRI) this has the Neuro uncomfortable about making a firm dx as yet. (In your sisters case, it does seem that MS is distinct possibility based on her clinical results and history . . . but they really like to see precisely what they are looking in the MRI too).

Did she have a spinal MRI or any other testing? Personally, I would push the Neuro to explain these lesions and neuro signs away, to try to determine where there seems to be doubt. If the Neuro is JUST looking for (yet) another piece of evidence, I would suggest that a spinal MRI, Evoked Potentials, or ANY other type of testing be done to firm up the MRI results. Personally, I wouldn't do an Spinal Tap again, except as a LAST resort.

Good luck!

Cherie