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Unenhanced and enhanced magnetic resonance imaging in the diagnosis of multiple sclerosis.

Initial enthusiasm about the role of magnetic resonance imaging (MRI) in the diagnosis of multiple sclerosis decreased substantially with the notion that (a) lesions of various pathological origins may resemble demyelinating plaques and (b) a dissemination of lesions throughout the brain is not unique for multiple sclerosis but may even be a "normal" finding. Current experience still does not allow the identification of the aetiology of a single hyperintensity but has identified multiple features of multiple sclerosis related signal abnormalities which, in combination, provide rather high diagnostic accuracy. Useful characteristics include the distribution of lesions such as a strictly periventricular, infratentorial or juxtacortical location, and involvement of the corpus callosum. The presence of contrast enhancement in some but not all lesions-that is, evidence of both old and new lesions-provides additional diagnostic support. Improved instrumentation for imaging of the spine further extends the diagnostic options. Intramedullary signal abnormalities are detected with increased sensitivity and may disclose the presence of multiple lesions even in patients with an equivocal or a negative MRI of the brain. The high sensitivity to plaques and the opportunity to simultaneously rule out other gross morphological damage justifies the use of MRI as the primary diagnostic modality in the evaluation of multiple sclerosis.