Fluid-attenuated inversion recovery ring sign as a marker of dysembryoplastic neuroepithelial tumors

Purpose: The aim of our study is to describe the hyperintense ring sign on fluid-attenuated inversion recovery (FLAIR) images in patients with dysembryoplastic neuroepithelial tumors (DNET), to discuss the radiopathologic correlation for this appearance, and to determine its role in preoperative diagnosis of DNETs. Materials and Methods: We retrospectively analyzed imaging features in 11 patients with pathological diagnosis of DNET. All patients had undergone surgery for refractory seizures. All had FLAIR imaging sequences performed on a 1.5-T magnetic resonance scanner. Clinical and pathological details in all cases were examined. Twenty-one age matched patients with pathologically confirmed low-grade glioma (n= 11), oligodendroglioma(n=2), and ganglioglioma (n = 9) in similar locations acted as control cases. Ten patients had follow-up imaging. Results: There were 11 patients with DNET (5 girl s and 6 boys). The age of presentation varied from 4 to 18 years (average, 9 years 1 month). Tumors were located in the temporal (n = 5), frontal (n = 4), parietal (n = 1), and occipital (n = 1) lobes. In 9 patients (82% sensitivity), the FLAIR images showed a well-defined hyperintense ring around these tumors, either as a complete or incomplete ring. Among the 21 control cases, the hyperintense ring sign was seen in 2 cases (90% specificity): one with low-grade glioma and one with ganglioglioma. Pathological evaluation of the DNETs suggested the hyperintense ring might correspond to the presence of peripheral loose neuroglial elements. Postoperative imaging showed partial residual ring in 3 patients, all of whom had persistent seizures. One patient had recurrent DNET at second surgery. Conclusion: Magnetic resonance imaging findings of DNET are well described. We describe an additional imaging sign, the hyperintense ring sign on FLAIR images, which is distinct and is fairly sensitive and specific for DNET. We believe this sign is a helpful adjuvant to preoperatively diagnose these tumors. The presence of this ring on postoperative imaging may indicate residual or recurrent tumor.