BACKGROUND- During the past decade, magnetic resonance imaging (MRI) has emerged as the single most useful tool in the diagnostic evaluation of multiple sclerosis (MS). More recently, MRI has evolved as a surrogate marker of disease activity. This review discusses the impact of MRI on the assessment and understanding of MS.
REVIEW SUMMARY- Brain MRI is the most sensitive imaging modality to detect demyelination in the central nervous system (CNS). MRI criteria developed to evaluate patients with MS have a diagnostic specificity of almost 100%. MRI has also been shown to have prognostic usefulness in patients who present with isolated neurologic syndromes suggestive of CNS demyelination. A normal brain MRI at presentation is consistent with a low risk of developing MS compared with a brain MRI with multiple T2-weighted lesions, which is associated with a high risk of developing clinically definite MS. Furthermore, total lesion load on the brain MRI has been found to correlate with cognitive dysfunction. Contrast-enhanced studies allow identification of lesions indicative of blood-brain barrier breakdown or active inflammation. Newer MRI techniques, including magnetic resonance spectroscopy and magnetization transfer ratio, provide further insight into the underlying pathological processes and characterization of individual lesions and lesion behavior over time. Fluid-attenuated inversion recovery sequence has been reported to increase the conspicuity of lesions in the brain and spinal cord of patients with MS. Finally, MRI is increasingly being used as a surrogate marker of disease activity in evaluating the efficacy of novel treatments for MS. This has had a major impact on the design of pilot studies in MS.
CONCLUSIONS- Our understanding and application of MRI in MS continue to improve. This is likely to result in greater diagnostic accuracy, stronger clinical correlation, and rapid identification of effective treatments in MS. Nevertheless, until such time, MRI findings should never be used in isolation to establish the diagnosis of MS or be the sole basis of judging the efficacy of a novel therapy.