MRI of long-term epilepsy-associated tumors.

In 20 to 30% of patients with long-term drug-resistant epilepsy neuroepithelial tumors, usually glioneuronal tumors are found. Gangliogliomas and dysembryoplastic neuroepithelial tumors (DNTs) are well characterized, both clinically and on MRI. Both tumor types are located in the cortex or in the cortex and subcortical white matter, gangliogliomas most commonly in the mesial temporal lobe ("around the collateral sulcus"). Both tumor types have typical imaging features, and from both, location and imaging features, they can be usually distinguished from glial tumors. This distinction is important since more than 70% of patients with drug resistant temporal lobe epilepsy caused by gangliogliomas and DNTs get seizure free following extended lesionectomy.