Abstract

Since its introduction in 1981 magnetic resonance imaging (MRI) has become the single most important paraclinical investigation in the diagnosis of multiple sclerosis (MS). Its sensitivity surpasses that of cerebrospinal fluid examination and trimodal evoked potentials. The clinical suspicion of multiple sclerosis remains mandatory because this greatly influences the specificity of MRI. Follow-up studies of MS patients using MRI with and without paramagnetic contrast enhancement have given us an insight in the 'realtime' dynamics of this disease which waxes and wanes for more than expected on clinical grounds alone. The impact of this 'subclinical' disease activity on the understanding of the disease and on the monitoring of therapeutical trials is discussed. The recently published European Community (EC) guidelines for the use of MRI in MS-related studies are the result of a major international effort to coordinate the multiple centers involved in MS related MRI research and should optimise multicentric (e.g. therapeutic trial) studies.