Is it possible to differentiate the impact of pediatric monophasic demyelinating disorders and multiple sclerosis after a first episode of demyelination?

A first episode of acute demyelination of the central nervous system may be a monophasic transient illness or represent the first attack of multiple sclerosis (MS). This study investigates if it is possible to distinguish these two groups of patients retrospectively at the time of the first episode, in a pediatric population. For each patient, the method consists in fitting an individual brain growth curve using multiple follow-up time-points, and using this curve to predict 4 metrics at the first attack: brain volume, brain growth rate, thalamus volume normalized by the brain volume (called normalized thalamus) and normalized thalamus growth rate. These metrics were compared to age-and-sex matched healthy controls by computing z-scores. In this study, 85 patients were scanned up to 8 years after the first attack. During this follow-up period, 23 patients were subsequently diagnosed with MS (MS group). Among the 62 patients with a transient illness, 9 suffered from monophasic acute disseminated encephalomyelitis (ADEM group). The 53 remaining formed the non-ADEM monophasic (MONO) group. The normalized thalamus growth rate was the only metric that distinguished patient groups: the z-scores were significantly smaller for MS than for the MONO group (p<0.01). Whereas 93% of monophasic subjects were correctly classified with a linear discriminant analysis, only 13% of the MS subjects were correctly classified, due to a large inter-individual variability in this group.