title: Fluid-attenuated inversion recovery ring sign as a marker of dysembryoplastic neuroepithelial tumors.
abstract: OBJECTIVE
  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.
  
  
  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 = 8) in similar locations acted as control cases. Ten patients had follow-up imaging.
  
  
  RESULTS
  There were 11 patients with DNET (5 girls 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Diagnostic Imaging, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada. parurad@hotmail.com
authors.forename: Hemant A
authors.initials: HA
authors.lastname: Parmar
authors.forename: Cynthia
authors.initials: C
authors.lastname: Hawkins
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Ozelame
authors.forename: Sylvester
authors.initials: S
authors.lastname: Chuang
authors.forename: James
authors.initials: J
authors.lastname: Rutka
authors.forename: Susan
authors.initials: S
authors.lastname: Blaser
mesh_terms: D000293:Adolescent; D001932:Brain Neoplasms / Q000473:pathology*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018302:Neoplasms, Neuroepithelial / Q000473:pathology*; D012189:Retrospective Studies
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA