Background: The ability to predict conversion to multiple sclerosis (MS) accurately when assessing a patient with a clinically isolated syndrome (CIS) is of paramount importance. Magnetic resonance imaging (MRI) is the best paraclinical tool currently available; however the significance of a history of an event suggestive of demyelination prior to CIS presentation has not been evaluated.
Methods: A retrospective chart review of all optic neuritis cases presenting as CIS to a single neuro-ophthalmologist in London, Ontario between 1990 to 1998 was performed. Data were collected regarding demographics, past medical history, history of present illness, and family history. Conversion to MS was determined by the McDonald criteria after ten years of follow-up. Bayesian statistics and logistic regression were used to determine the best predictors of conversion to MS from CIS.
Results: One hundred and sixteen optic neuritis subjects were included in the analysis. After ten years, 42.2% had converted to MS. The best predictor of future conversion remained at least one brain lesion, disseminated in space, on MRI (sensitivity 0.90, specificity 0.75). However, if the subject additionally had a history suggestive of a demyelinating event in the past that had not been confirmed clinically, the specificity increased to 0.96. These two traits taken together had an odds ratio of 27.8 for conversion to MS in the next ten years (p<0.001).
Conclusions: A history of an event suggestive of demyelination prior to presenting with optic neuritis as CIS increases the ability of the clinician to predict conversion to MS in the next ten years.