Magnetic resonance imaging at baseline and follow-up to differentiate between pediatric monophasic acquired CNS demyelination and MS

Abstract

BackgroundIt is essential to distinguish acute disseminated encephalomyelitis (ADEM) from MS early. Our aim was to determine MRI features at baseline and follow-up to distinguish pediatric ADEM from MS stratified according to age at onset. MethodsUsing hospital ICD-10 codes for acquired demyelinating syndromes from a nationwide register and subsequent chart review, we identified 52 children (<18 years) with ADEM and 66 children with MS. We undertook a retrospective analysis of MRI scans at onset and at follow-up. The MRI rater was a senior neuroradiologist blinded to clinical characteristics. ResultsAt baseline, children with ADEM had more diffuse poorly demarcated lesions, particularly in the basal ganglia/thalamus (p = 0.001) and cerebellar peduncles (p < 0.0001). Further, longitudinal extensive transverse myelitis was strongly associated with ADEM (p<0.0001). Children with ADEM had fewer contrast-enhancing lesions (p = 0.0004), occipital lesions (p = 0.01), optic nerve lesions (p = 0.01), periventricular lesions, well-defined lesions only (p<0.0001), and fewer fulfilled dissemination in time according to the McDonald 2017 criteria (p = 0.005). On baseline MRI, dissemination in space and time was fulfilled in 17% of children with ADEM and in 34% of children with MS (p = 0.06), and 60% of children with ADEM fulfilled the criterion for dissemination in space. The mean time from baseline MRI to follow-up MRI was 1.0 year for children with ADEM and 2.1 years for children with MS. On follow-up MRI, 85% of children with ADEM had partial or complete T2 lesion resolution, but in the 58% without complete resolution lesions were predominantly frontal. Only 47% of children with MS had partial or complete T2 lesion resolution, and therefore more MRI features differed between children with ADEM and MS on follow-up. MRI had the greatest distinguishing value after age 11 years because MS is exceptional in the first decade of life. ConclusionAge at onset and the timing of MRI in relation to disease onset are critical in the interpretation of MRI to distinguish between ADEM and MS.