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An Unusual Presentation of Dysembryoplastic Neuroepithelial Tumor as a Fourth Ventricular Mass

Materials & Methods Dysembryoplastic neuoepithelial tumors (DNTs) typically occur in children and young adults with pharmacoresistant complex partial seizures. Radiographically, DNTs are generally cortically based tumors, predominately supratentorial in location, most commonly within the temporal lobe, and are frequently associated with cortical dysplasia. To our knowledge, there are only four reports describing the histologic features of DNTs in the posterior fossa and no reports of fourth ventricular DNTs. The authors present a case in which a tumor occurred in the fourth ventricle of a 13-year-old girl presenting with a 3-week history of headaches. Unenhanced CT of the head demonstrated obstructive hydrocephalus as a result of a low density mass (H.U. 15) within the fourth ventricle. On MR imaging, the 4.0 cm diameter nonenhancing mass was centered within the fourth ventricle and extended superiorly into the quadrigeminal plate and superior cerebellar cisterns. The lesion was low in signal on T1, high in signal on FLAIR. The lesion was predominately high in signal on T2 with a "speckled" appearance and was normal to slightly increased in signal with diffusion. MR spectroscopy showed an elevated choline-to-creatinine ratio, decreased NAA, and a possible small lactate peak.