Early factors associated with later conversion to multiple sclerosis in patients presenting with isolated myelitis

Objective To identify early clinical and paraclinical factors that may help predict later conversion to multiple sclerosis (MS) in patients presenting with isolated myelitis (ie, 'transverse myelitis' without clinical or radiological evidence of inflammation/demyelination elsewhere in the central nervous system). Methods In this retrospective cohort study, we included patients with isolated myelitis who were followed clinically and radiologically at our specialised myelopathy clinic. We excluded patients with MS at the onset, aquaporin-4-IgG seropositivity, myelin oligodendrocyte glycoprotein-IgG seropositivity or other identified aetiology. Logistic regression was used to identify factors predictive of conversion to MS (defined by the 2017 McDonald criteria). Results We included 100 patients, followed for a median of 4.3 years. Conversion to MS occurred in 25 of 77 patients (32%) with short-segment myelitis (longest lesion spanning <3 vertebral segments on MRI) as compared with 0 of 23 patients (0%) with longitudinally extensive myelitis (p=0.002). Among patients with short-segment myelitis, factors identified as highly predictive of conversion to MS using multivariate logistic regression included cerebrospinal fluid (CSF)-restricted oligoclonal bands (OCB) (OR (OR) 9.2, 95% CI 2.1 to 41.0, p=0.004), younger age (OR 1.1 for each year younger, 95% CI 1.0 to 1.1, p=0.04) and longer follow-up (OR 1.3 for each year longer, 95% CI 1.0 to 1.6, p=0.04). Conversion to MS occurred at a median of 2.8 years after myelitis onset. Conclusions Short-segment MRI cord lesion(s), CSF-restricted OCB, younger age and longer follow-up are all factors predictive of conversion to MS in patients presenting with isolated myelitis.