RESUMO
Paraneoplastic neurologic syndromes are a rare and heterogeneous group of immune-mediated syndromes caused by underlying solid and nonsolid tumors. We present a case of 8-year-old female with long history of mild headaches and central instability who presented multiple poorly defined signal abnormalities at the subcortical white matter of both cerebral hemispheres and cerebellar atrophy on brain magnetic resonance imaging. Further studies revealed a posterior mediastinum ganglioneuroma derived from a mature ganglioneuroblastoma that was treated with surgery. Two paraneoplastic neurologic syndromes were considered: Anti-N-Methyl-D-Aspartate Receptor (NMDAR) encephalitis due to the resolution of subcortical signal abnormalities after mediastinal mass resection and opsoclonus-myoclonus-ataxia syndrome due to cerebellar atrophy. Intertnational guideline established the criteria for definite diagnosis of paraneoplastic neurologic syndromes and detection of onconeural antibodies is not mandatory for their diagnosis. Paraneoplastic neurologic syndromes may appear several years before the tumor is detected.