Dysembryoplastic neuroepithelial tumor (DNET) associated with dysgenesis of the corpus callosum
Presentation
A young patient presented with long-standing epilepsy.
Patient Data
The axial contrast-enhanced CT study shows a relatively well-demarcated cortically-based hypoattenuated lesion involving the lower posterior right frontal lobe, including the right inferior subcentral gyrus, without significant enhancement, mass effect, or calcification. The study also shows features suggestive of corpus callosum agenesis.
The MRI study shows a well-demarcated cortically-based lesion that appears with a hyperintense signal on T2WI, with a bubbly appearance, and hypointense in T1WI without significant enhancement or mass effect. A thin, hyperintense rim is seen in the FLAIR study. Subtle scalloping of the overlying cranial bone is seen, denoting chronicity. Features of partial agenesis of the corpus callosum (CC) are also noted, manifested by the absence of the body and splenium of the CC, with relative preservation of the genu and rostrum. The lateral ventricles show a typical "racing car" appearance on the axial plane.
Case Discussion
The differential diagnosis in this particular case is between DNET and a low-grade glioma. The imaging characteristics and presentation of the patient align more favourably with the former.
Dysembryoplastic neuroepithelial tumor (DNET) is a unique type of low-grade glioneuronal tumor, usually presenting with childhood or adolescent epilepsy refractory to medical treatment. DNETs are slow-growing tumors arising from the cerebral cortex, usually involving an entire gyrus or a wedge-shaped part of a cerebral lobe. Pathologically, typical DNETs comprise the tumor core surrounded by the rim of dysplastic cortex; this rim of dysplastic cortex is regarded as highly epileptogenic. Complete resection of the tumor is crucial for seizure control. DNET appears on CT as a low-attenuating cortically-based mass with extension into the subcortical area. MRI is the imaging modality of choice for diagnosing DNET. It usually demonstrates a bubbly appearance with low signal intensity on T1W images and high signal on T2W images and FLAIR, without noticeable enhancement. Poor enhancement is a common feature that distinguishes DNET from gangliogliomas, which usually show intense enhancement.
Dysgenesis of the corpus callosum represents an in-utero developmental anomaly characterized by incomplete corpus callosum development. It is associated with many other CNS anomalies, including Chiari II malformation, Dandy-Walker spectrum, and grey matter heterotopia. However, no clearly proven association between this anomaly and DNET exists.
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