Dysembryoplastic neuroepithelial tumors (DNET) are benign (WHO Grade I) slow growing glioneuronal tumours arising from cortical or deep grey matter. The vast majority are centred in cortical grey matter, arise from secondary germinal layers, and are frequently associated with cortical dysplasia (80%). They characteristically cause intractable partial seizures.

Epidemiology 

Typically these tumours are diagnosed in children or young adults, as a result of the investigation of seizures, which have usually had childhood onset. Only a slight male predilection is present. 

MRI features

T1: generally hypointense compared to adjacent brain

T1 C+ (Gd):may show enhancement in ~20-30% of cases. The enhancement may be heterogeneous or a mural nodule.

T2: generally high signal with a 'bubbly appearance'

FLAIR: mixed signal intensity with bright rim sign, partial suppression of some of the "bubbles"

DWI: There is no restricted diffusion