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SAN FRANCISCO, Dec. 10 -- Widespread use of MRI for conditions like migraine and head trauma is turning up what looks like evidence of multiple sclerosis -- even if patients have no symptoms of the disease, researchers said here.

Nearly a third of these patients develop MS within about five years, Darin T. Okuda, M.D., of the University of California San Francisco, and colleagues reported online in Neurology.

The researchers have dubbed the condition "radiologically isolated syndrome" (RIS), which describes the incidental white matter image findings that are suggestive of MS pathology.

"More research is needed to fully understand the risk of developing MS for people with these brain abnormalities, but it appears that this condition may be a precursor to MS," Dr. Okuda said.

For their study, the researchers looked at scans from 44 patients (41 female) who had these white matter anomalies on MRIs done for, among other reasons, migraine, craniocerebral trauma, vertigo, and panic attacks.

Neurological assessments performed at the time of those MRIs were normal, the researchers said.

Of those patients, 30 had longitudinal clinical follow up.

Nearly a third of those patients (10 out of 30) developed symptoms of MS within an average of 5.4 years, the researchers said.

Among 41 of the original patients who had additional follow-up MRI, 24 (59%) had evidence of radiologic progression -- new or larger lesions -- over a median time period of 2.7 years, the researchers said.

"The observed shorter time to radiologic progression compared with clinical progression may reflect the highly sensitive nature of MRI technology and previous observations that the development of new MS plaques outnumbers the occurrence of new relapses," the researchers said.

Patients who had lesions on the initial MRI scans had an increased risk of developing new or larger lesions on subsequent scans (HR 3.4, 95% CI 1.3 to 8.7, P=0.01).

So the researchers concluded that patients with radiologically isolated syndrome are at increased risk of developing clinical symptoms of MS or experiencing radiologic progression.

"It appears that RIS may be a precursor to MS," the researchers concluded, acknowledging that more research is needed to confirm their findings.

But editorialists Dennis Bourdette, M.D., and Jack Simon, M.D., Ph.D., both of Oregon Health & Science University, said patients with the new radiologically isolated syndrome should definitely not be considered to have early MS.

They also said patients should not be treated with a disease-modifying therapy, even though seven patients in the study had received MS treatment before being referred to the prospective study.

"Even patients who show radiologic progression cannot be considered to have MS if they have no symptoms of the illness," they wrote, because other conditions mimic MS radiologically, making a reliable diagnosis challenging.

Also, they pointed out, some patients may have pathologic changes of MS but remain permanently asymptomatic.

"This study sets the stage for establishing a process for evaluating these patients and following them to help determine the risk of developing MS," Dr. Bourdette said. "For now, it's best to remember the wise advice that we 'treat the patient, not the MRI scan.'"