A rare central nervous system tumor of childhood with spongiform appearance on brain magnetic resonance imaging; primary diffuse leptomeningeal oligodendrogliomatosis.

Primary diffuse leptomeningeal oligodendrogliomatosis is a rare fatal tumor of childhood. Symptoms usually occur when the tumor causes hydrocephalus. Brain magnetic resonance imaging (MRI) may be nearly normal in the early stages of the disease, while hydrocephalus and multiple leptomeningeal cysts with spongiform appearance may appear later on. One may consider the diagnosis when radiologic findings become apparent with multiple leptomeningeal cysts. However, failure to recognize the imaging findings due to the rarity of the disease may delay the diagnosis. Here, we report a 3.5-year-old girl who presented with ataxia and vomiting and had a diagnosis of primary diffuse leptomeningeal glioneuronal tumor with remarkable brain MRI findings as diffuse multiple tiny cystic lesions on the brain and spinal cord. She benefited from radiotherapy and temozolomide treatment with remission of brain MRI findings. Increasing the number of reported cases will enable the elucidation of the disease's pathogenesis and the development of treatment protocols.