Fig.4
Fig.5
Fig.6
Fig.1
Fig.2
Fig.3Click on Images for Enlarged View
Findings: T1-weighted coronal Turboflash images (Figs 1 and 2) and T1-weighted axial spin-echo images (Fig 5) demonstrate a well-defined, lobulated, low-signal mass involving the cortex and subcortical white matter of the left temporal lobe. The mass does not enhance following Gadolinium administration (Figs 3 and 6). The lesion is high in signal on the T2-weighted coronal images (Fig 4). It exhibits mild mass effect but there is no significant associated vasogenic edema.
Diagnosis: Dysembryoplastic Neuroepithelial Tumor
Discussion: Dysembryoplastic Neuroepithelial Tumor (DNT) is a recently recognized, benign tumor associated with medically intractable, partial complex seizures. Mean age of onset of symptoms is nine years (range 1-19 years). All reported DNT's have been supratentorial, most often involving the temporal lobe (approximately 2/3) followed in frequency by the frontal lobe (1/3). The tumors are primarily cortical in location, although they may extend to involve the subcortical white matter. On CT scans, DNT's are well-defined, low-attenuation lesions which may be mistaken for cysts. The tumors tend to be low signal on T1- weighted MR images and high signal on T2-weighted images, i.e., similar to CSF, but on proton-density images, they are slightly higher in signal than CSF, allowing them to be differentiated from simple cysts. Less than 25% calcify or enhance. There is associated calvarial remodeling in approximately 1/3 of cases.
Differential diagnoses include ganglioglioma and low-grade astrocytoma. A ganglioglioma, however, is more likely to be located within the white matter. Calvarial remodeling, if present, is a helpful differentiating feature in that it would be unlikely for either a ganglioglioma or a low-grade astrocytoma to cause such changes.
The prognosis for patients with DNT is excellent. 70-81% of patients are seizure-free following surgery, and the tumor does not recur, even in cases where resection is considered incomplete.
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