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Dysembryoplastic neuroepithelial tumors current: concepts and clinical management in 2006 Volume 18, issue 2, Avril-Mai-Juin 2006

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Authors
Service de neurochirurgie, Centre hospitalier Sainte-Anne, Paris

Dysembryoplastic neuroepithelial tumors (DNTs) correspond to indolent tumors of glial origin located into the cortex, mostly in the temporal lobe. The main manifestation consists of partial intractable epilepsy starting in childhood or in young adult, without any neurological associated symptoms. Focal EEG abnormalities are concordant with the location of the lesion in 3/4 of the cases. MRI characteristics consist of cortical topography, hyposignal or isosignal T1 and hypersignal T2 or FLAIR, without mass effect or perilesional oedema. Several patterns have been described : type 1 « pseudocystic ou pseudopolycystic », corresponding to histological simple or complex specific forms ; type 2 « homogeneous or heterogeneous megagyric » corresponding to non specific forms ; type 3 « diffuse » associated with severe cortical dysplasia. Intralesional interictal activities recorded during stereo-EEG consist of spikes or poly-spikes associated with depression of activity. Intralesional ictal discharge onset demonstrates intrinsic epileptogenicity of DNTs. Epileptogenic zone (EZ) widespread depends of lesional location and structure. EZ coincides with the lesion in simple or complex histological forms and includes perilesional areas in non specific forms, especially when severe cortical dysplasia is found. Epilepsy can be cured by surgery in 80 % of the cases. The resection may be limited to tumoral tissue or extended to perilesional areas. A corticectomy including the mesial temporal structures may be associated according to the EZ extent.