September 8, 2003
Laurie Barclay, MD
New guidelines from the American Academy of Neurology, published in the Sept. 9 issue of Neurology, suggest that magnetic resonance imaging (MRI) helps diagnose multiple sclerosis (MS) faster, rather than waiting for evidence of dissemination over time. Studies show that early treatment can lessen disease activity and severity, but that if MS is left untreated in the early stages, the disease is more resistant and can accelerate more rapidly.
"Before, the criteria used to diagnose people required neurologists to show that disease activity had occurred in the brain over time," lead author Elliot Frohman, MD, PhD, from the University of Texas Southwestern Medical School in Dallas, says in a news release. "People would have to wait for a diagnosis. Now that we have evidence showing that early treatment can reduce the entire course of the disease, we really needed to ask the question about how early the diagnosis can be made."
After review of the MEDLINE database from 1966 to 2003, the investigators concluded that in many cases, findings on a single MRI of the brain and spinal cord can be a strong predictor of future MS. Occult disease activity on MRI may be apparent in 50% to 80% of patients when they first present with a clinically isolated syndrome. However, the guidelines recommend that neurologists consider MRI information in the context of each patient's specific situation.
In a young to middle-aged adult with a clinically isolated syndrome, once other possible diagnoses have been ruled out, the finding of three or more brain lesions in white matter on a T2-weighted MRI (especially if one of the lesions is in the periventricular region) predicts development of clinically definite MS within the next seven to 10 years with greater than 80% sensitivity.
Similarly, two or more gadolinium-enhancing lesions at baseline and the appearance of new T2 lesions or new enhancement on follow-up scans are also highly predictive of the development of clinically definite MS in the near future. Normal MRI results at presentation make future development of clinically definite MS much less likely.
"This guideline helps us use MRI to telescope into the future to see what's going to happen with these patients," Dr. Frohman says. "The evidence allows us to predict with more certainty who will develop MS, which allows us to begin helpful treatment earlier than in the past."
The available evidence suggests that early treatment of clinically isolated syndromes of MS with MRI abnormalities lessens disease activity and severity, whereas lack of treatment in the early stages is associated with an accelerated course and with greater resistance to treatment.
"With this knowledge and the fact that the current drugs for MS have few downsides except for cost and minor side effects, there's not much sense in waiting for more disability and more attacks to occur," Dr. Frohman says.
Current criteria are not sufficiently sensitive to identify many patients who already have MS at the time of their first attack, and these criteria recommend waiting for additional signs of disease activity before making the diagnosis. The current criteria also do not account for specific distribution of lesions on MRI and thus may lead to an unjustified diagnosis of MS.
"In some ways, that's like waiting for the other shoe to drop," Dr. Frohman says. "If the majority of these patients have MS and waiting could compromise how we can affect the course of the disease, then we need to go ahead and treat them."
In an accompanying editorial, Jack H. Simon, MD, PhD, from the University of Colorado Health Sciences Center in Denver, and Alan J. Thompson, MD, from the Institute of Neurology in London, U.K., recommend additional long-term follow-up studies of MRI predictors of MS diagnosis. They note that the criterion of dissemination of lesions in space can be helpful in borderline cases.
"Despite advances in MRI, MS remains a clinical diagnosis dependent on a high level of clinical expertise to distinguish symptoms indicative of a clinically isolated syndrome versus those of ongoing disease activity," they write. "The pressure to diagnose early inevitably leads to a tension between secure diagnosis and prevention or at least amelioration of early deficit."
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