Evolution of MRI abnormalities in paediatric acute disseminated encephalomyelitis.

Objective: Acute disseminating encephalomyelitis (ADEM) is an inflammatory demyelinating disease affecting the central nervous system and mainly occurs in young children. Children who initially presented with ADEM can be diagnosed with multiple sclerosis (MS) in case new non-encephalopathic clinical symptoms occur with new lesions on MRI at least three months after onset of ADEM. We aim to study the timing of MRI abnormalities related to the evolution of clinical symptoms in our Dutch paediatric ADEM cohort.

Methods: The Dutch database for acquired demyelinating syndromes (ADS) was screened for children under age eighteen fulfilling the international consensus diagnostic criteria for ADEM. Children were eligible when the first MRI was performed within the first three months after onset of clinical symptoms and at least one brain follow-up MRI was available for evaluation. Forty-two children with ADEM were included (median age four years two months). All available MRIs and medical records were assessed and categorised as 'improved', 'deteriorated' and 'unchanged'.

Results: We found that during clinical recovery, new lesions and enlargement of existing MRI lesions occurred in the first three months in about 50% of the performed MRIs. In contrast, this was rarely seen more than three months after first onset of ADEM.

Conclusion: We recommend to perform a brain MRI as a reference scan three months after onset. Follow-up imaging should be compared with this scan in order to prevent an incorrect diagnosis of MS after ADEM.