Dysembryoplastic neuroepithelial tumour

Clinical History

An 18-year-old male patient presented to the hospital with a history of seizures lasting for several months even under antiepileptic medication. The neurological examination showed no abnormalities.

Imaging Findings

Brain MR revealed a cortical well-marginated intra-axial mass within multiple septae, located in the superficial left temporal lobe and measuring 28x34x24 mm. The lesion had a heterogeneous signal, hypointense on T1 (Fig. 1), high signal on T2 (Fig. 2) and hyperintense signal on flair at the borders (Fig. 3). The contrast enhancement was faint (Fig. 4).

Discussion

Dysembryoplastic neuroepithelial tumour (DNET) is known to be a cause of seizures that occur characteristically in the cerebral cortex of children and young adults. Daumas-Duport et al. described the following features of DNET: [1] intracortical location; [2] partially nodular structure; [3] mixed glial and neuronal composition, [4] cortical dysplasia in the adjacent cortex.
Despite their heterogeneous morphological appearance, DNET share the same clinical presentation of drug-resistant epilepsy starting at an early age. In about 90% of cases, the first seizure happens before 20 years of age [1]. Although, DNET shows a predilection for the temporal lobe [5], reports revealed new DNET locations, including the pons, thalamus, basal ganglia, cerebellum, and third ventricle [6]. Among these “ectopic” locations, the basal ganglia/lateral ventricle has been the most common site.
On MR imaging, DNETs most commonly manifest as intracortical masses, hypointense on T1-weighted images and hyperintense on T2-weighted images without surrounding perilesional oedema or signs of mass effect. Some lesions may appear as an enlarged heterogeneous gyrus, with delicate septa-like structures that are visible within the lesion, producing a soap-bubble appearance at the cortical margin [7]. In some cases, the lesions have a cortical base and an apex pointing toward the lateral ventricle giving the appearance of a comet-tail [7]. The FLAIR hyperintense rim sign [7] is described as a thin rim of well-defined hyperintensity at the borders of the DNET, separating it from the surrounding normal brain. Contrast enhancement is relatively rare (12%).
DNETs are ‘‘benign’’ lesions and do not require chemotherapy or radiotherapy. The recognition of this tumour is very important because it is surgically curable. However, DNETs can recur, and are sometimes surrounded by areas of cortical dysplasia which may be responsible for surgical failure [8].
TEACHING POINT
- Diagnosis of dysembryoplastic neuroepithelial tumours (DNETs) is based on a combination of findings: a cortical-based mass in a young patient manifesting intractable seizures with a typical soap-bubble appearance, and without mass effect or perilesional oedema on MRI.
- Recognition of DNETs is important because surgical resection is curative with a good prognosis.

Differential Diagnosis List

Final Diagnosis

Dysembryoplastic neuroepithelial tumour

URL:	https://www.eurorad.org/case/13604
DOI:	10.1594/EURORAD/CASE.13604
ISSN:	1563-4086