title: Chordoid Meningioma: Differentiating a Rare World Health Organization Grade II Tumor from Other Meningioma Histologic Subtypes Using MRI.
abstract: OBJECTIVE
  Meningiomas are very commonly diagnosed intracranial primary neoplasms, of which the chordoid subtype is seldom encountered. Our aim was to retrospectively review preoperative MR imaging of intracranial chordoid meningiomas, a rare WHO grade II variant, in an effort to determine if there exist distinguishing MR imaging characteristics that can aid in differentiating this atypical variety from other meningioma subtypes.
  
  
  METHODS
  Ten cases of WHO grade II chordoid meningioma were diagnosed at our institution over an 11-year span, 8 of which had preoperative MR imaging available for review and were included in our analysis. Chordoid meningioma MR imaging characteristics, including ADC values and normalized ADC ratios, were compared with those of 80 consecutive cases of WHO grade I meningioma, 21 consecutive cases of nonchordoid WHO grade II meningioma, and 1 case of WHO grade III meningioma.
  
  
  RESULTS
  Preoperative MR imaging revealed no significant differences in size, location, signal characteristics, or contrast enhancement between chordoid meningiomas and other meningiomas. There were, however, clear differences in the ADC values and normalized ADC ratios, with a mean absolute ADC value of 1.62 ± 0.33 × 10(-3) mm(2)/s and a mean normalized ADC ratio of 2.22 ± 0.47 × 10(-3) mm(2)/s in chordoid meningiomas compared with mean ADC and normalized ADC values, respectively, of 0.88 ± 0.13 × 10(-3) mm(2)/s and 1.17 ± 0.16 × 10(-3) mm(2)/s in benign WHO grade I meningiomas, 0.84 ± 0.11 × 10(-3) mm(2)/s and 1.11 ± 0.15 × 10(-3) mm(2)/s in nonchordoid WHO grade II meningiomas, and 0.57 × 10(-3) mm(2)/s and 0.75 × 10(-3) mm(2)/s in the 1 WHO grade III meningioma.
  
  
  CONCLUSIONS
  Chordoid meningiomas have statistically significant elevations of ADC and normalized ADC values when compared with all other WHO grade I, II, and III subtypes, which enables reliable preoperative prediction of this atypical histopathologic diagnosis.
authors.affiliation: From the Departments of Neuroradiology (J.B.P., T.G.M., Z.F.Y., D.B.M.) jasonbpond@gmail.com.
authors.forename: J B
authors.identifier: http://orcid.org/0000-0002-4120-6035
authors.initials: JB
authors.lastname: Pond
authors.affiliation: From the Departments of Neuroradiology (J.B.P., T.G.M., Z.F.Y., D.B.M.).
authors.forename: T G
authors.initials: TG
authors.lastname: Morgan
authors.affiliation: Neuropathology (K.J.H.).
authors.forename: K J
authors.initials: KJ
authors.lastname: Hatanpaa
authors.affiliation: From the Departments of Neuroradiology (J.B.P., T.G.M., Z.F.Y., D.B.M.).
authors.forename: Z F
authors.initials: ZF
authors.lastname: Yetkin
authors.affiliation: Neurosurgery (B.E.M.), University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: B E
authors.initials: BE
authors.lastname: Mickey
authors.affiliation: From the Departments of Neuroradiology (J.B.P., T.G.M., Z.F.Y., D.B.M.).
authors.forename: D B
authors.initials: DB
authors.lastname: Mendelsohn
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D016545:Choroid Plexus Neoplasms / Q000175:diagnosis*; D003937:Diagnosis, Differential; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008577:Meningeal Neoplasms / Q000175:diagnosis*; D008579:Meningioma / Q000175:diagnosis*; D008875:Middle Aged; D012189:Retrospective Studies