[Dysembryoplastic neuroepithelial tumors. A benign tumor cause of partial epilepsy in young adults].

Dysembryoplastic neuroepithelial tumor (DNT) is a newly recognized brain lesion first reported in 1988 by Daumas-Duport et al. The authors described five cases of DNT, that occurred in young people and were characterized by partial seizures. Seizures could become intractable and secondary generalised. Usually, the interictal neurological examination was normal. In most cases, computed tomography showed a supratentorial, "pseudocystic" low density appearance associated in some cases with calcific hyperdensity or focal contrast enhancement. Magnetic resonance imaging demonstrated a predominantly intracortical lesion. Common features included low signal intensity on T1-weighted images and high signal on T2-weighted images. Temporal and frontal lobes were mainly involved. Dysembryoplastic origin explained the clinical and radiological stability and the benign evolution of this tumor. Tumor resection was required only when epilepsy was intractable or when there was intracranial hypertension. Earlier intervention can prevent the physical and psychosocial damage resulting from chronic seizures and can improve the prognosis for these young patient. Histologically, DNT have been incorporated amond the category of neuronal and mixed neuronoglial tumors. Three patterns are described: a simple form with a unique glioneuronal element, a complex form with specific glioneuronal element, nodules being made of multiple variants looking like astrocytomas, oligodendrogliomas or oligo-astrocytomas, foci of dysplastic cortical disorganisation, and a non specific form. When specific glioneuronal composant is absent (50% of cases), the identification of DNT has therapeutic and prognostic implications because aggressive therapy may be avoided, sparing these young patients the long term effects of radio-or chemotherapy.