Experts answer MS questions.

The short answer is yes -- although MRI is a very helpful tool when MS is suspected. Changes seen on MRI are not specific to MS. This means that if we find some white spots (technically, areas of increased signal) on an MRI, it doesn't mean the person has MS. There can be many reasons for areas of increased signal. They can even occur as a normal variation.

The diagnosis of MS ultimately depends on the person's medical or clinical history and the neurological exam. If the clinical history raises the suspicion of MS, and the MRI is consistent with MS -- then the likelihood that MS is the right diagnosis increases a great deal. Studies show that about 90 percent of people who have both a history of problems and exam findings that suggest MS also have changes on their MRIs.

On the other hand -- if we find no changes on the MRI but the person has a history of problems and exam findings that suggest MS, we may still suspect MS or we may make the diagnosis if these other findings are sufficiently strong. Some people with MS have changes only in the spinal cord, a much harder area to study using MRI.

But if a person's medical history doesn't point clearly to MS and the MRI is normal, I'd be very cautious. I would probably try other tests, including evoked responses and examinations of fluid obtained by spinal tap. Changes consistent with MS in either of these areas would help establish diagnosis.

A definite diagnosis of MS requires evidence that different parts of the central nervous system are involved at different times. Only part of this information can come from MRI.