Dysembryoplastic neuroepithelial tumor

Dysembryoplastic neuroepithelial tumor (DNET or DNT) is a rare, benign (WHO grade I) brain tumor that arises from the cerebral cortex. It is classified as a glioneuronal tumor, meaning it is composed of both glial and neuronal cell elements. DNETs most commonly occur in the temporal lobe, though they can develop in other cortical regions. These tumors are believed to originate during embryonic brain development, which is reflected in their name. The hallmark clinical feature of DNET is drug-resistant (medically intractable) focal epilepsy, which typically begins in childhood or adolescence. Seizures are often partial complex seizures and may be present for many years before diagnosis. Neurological examination is usually otherwise normal, and most patients have preserved cognitive function, though some individuals may experience learning difficulties or mild neurological deficits depending on tumor location. On MRI, DNETs characteristically appear as well-circumscribed, multicystic cortical lesions that may have a "bubbly" appearance, often without surrounding edema or mass effect. DNETs are slow-growing tumors with an excellent prognosis. They rarely undergo malignant transformation. The primary treatment is surgical resection (lesionectomy), which is particularly indicated for patients with medically refractory epilepsy. Complete surgical removal often results in seizure freedom in a high proportion of patients, with reported seizure-free rates of 60–90% following surgery. Chemotherapy and radiation therapy are generally not required. Long-term follow-up is recommended to monitor for recurrence, though recurrence rates are low after complete resection. For patients whose seizures are well-controlled with antiepileptic medications, observation with serial imaging may be considered.

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