Evolving Cognitive Dysfunction in Children with Neurologically Stable Opsoclonus-Myoclonus Syndrome.

Cognitive and acquired neurodevelopmental deficits have been reported in children with opsoclonus-myoclonus syndrome (OMS) and are known to be associated with more severe and relapsing disease course. However, there is a paucity of data regarding cognitive dysfunction in children with stable neurological disease. We report three children with OMS and evolving cognitive dysfunction in the context of a mild disease course. The children's ages at disease onset were between 17 and 35 months and they were followed up for 4-10 years. Neuroblastoma was identified in one child. OMS severity scores ranged between 8 and 12/15 at presentation. They underwent immunotherapy and all were in remission by 7 months (range 4-13 months), with treatment maintained for 1 year. One child remained relapse-free, while two others had one clinical relapse each and were immunotherapy-responsive again. In all cases, evolving cognitive dysfunction was reported despite being in remission and stable off treatment for a median of 20 months (range of 12-31 months; two OMS scores of 0/15 and one of 2/15). In children with OMS who have completed treatment and have made full or near full neurological recovery, concerns remain regarding long-term outcome in terms of future learning and cognitive development.