[Opsoclonus-myoclonus syndrome in a 2 year old boy with prenatally diagnosed retroperitoneal tumour].

Opsoclonus-myoclonus syndrome, also named Myoclonic Encephalopathy of Infants, Opsoclonus- Myoclonus Ataxia, Dancing Eyes - Dancing Feet Syndrome, Dancing Eyes Syndrome, Kinsbourne syndrome, is a rare, paraneoplastic or possibly post-viral chronic neurological disorder. The age of presentation ranges from 6 months to 3 years. In 50% of affected children the syndrome is associated with an underlying occult or clinically apparent neuroblastoma. In most patients the tumour is localized, small and well differentiated, with no NMYC gene copy number amplification. The syndrome may also occur after tumour resection or at relapse. The opsoclonus-myoclonus syndrome can occur in children without neuroblastoma, in such idiopathiccases, the onset of neurological symptoms is related to infection. It is assumed, that in idiopathic cases the syndrome could have developed in the course of neuroblastoma which had undergone a complete spontaneous regression. The most characteristic clinical features of opsoclonus-myoclonus syndrome are: opsoclonus, myoclonus, ataxia, irritability, mutism and sleep disturbances. The disease course is usually long-term with episodes of remission and relapses. Approximately 80% of children with opsoclonus-myoclonus syndrome suffer from mild to severe neurological handicaps, mainly cognitive impairment. The authors present a 2-year old boy with opsoclonus-myoclonus syndrome preceded by involution of prenatally documented retroperitoneal area tumour.