Objectives Using current diagnostic criteria, patients who present with a clinically isolated syndrome (CIS) may develop multiple sclerosis (MS) by subsequently exhibiting dissemination in space and time on clinical (clinically definite (CD) MS) or radiological (MRI) grounds. This study investigated the frequency of radiological without clinical conversion to MS after long term follow-up as this has not previously been defined.
Methods Two cohorts who underwent serial clinical and MRI studies from presentation with a CIS and who were followed-up over a mean of 6 and 20 years were investigated. The distribution and formation of lesions visible on brain MRI were assessed using the revised McDonald criteria (2005). Radiologically defined (RD) MS was determined by fulfilment of the MRI but not the CDMS criteria.
Results 105 people were followed-up for 6 years after a CIS, of whom 51% developed CDMS, 15% RDMS and the remainder were classified as still having had a CIS. 70 people were followed-up at 20 years, of whom 61% and 11% had developed CDMS and RDMS, respectively.
Conclusion About 10–15% of CIS patients may develop MS on MRI criteria only, without further clinical events for up to two decades.
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Funding The NMR Research Unit is supported by the MS Society Great Britain and Northern Ireland, and Department of Health's NIHR Comprehensive Biomedical Research Centre at UCLH.
Competing interests CMD received funding from Novartis, through a grant held by the UCL Institute of Neurology, to perform MRI analysis. AJT has received honoraria for consulting services, speaking and serving on scientific advisory boards from Novartis, Eisai, Weleda/Society for Clinical Research, Hoffman La Roche, UCB Pharma, Serono Foundation, Sanofi-Aventis and the MS Society of Great Britain and Northern Ireland. He is editor-in-chief of Multiple Sclerosis for which he receives an honorarium from Sage Publications. DHM has received honoraria from UCB Pharma, Schering, Biogen Idec, GSK and Wyeth for consulting services, speaking and serving on scientific advisory boards. He has received reimbursement for work as co-chief editor of Journal of Neurology and research grant support from the MS Society of Great Britain and Northern Ireland, Wellcome Trust, Medical Research Council UK, Biogen Idec, Novartis, GlaxoSmithKline and Schering. GTP is editor-in-chief of Neuro-Ophthalmology and the Institute of Neurology has received payments in respect of this work.
Ethics approval This study was conducted with the approval of the National Hospital for Neurology and Neurosurgery and UCL Institute of Neurology Joint Research Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.