title: Benign osteoblastoma of the odontoid process of the axis: a case report.
abstract: BACKGROUND
  The majority of benign spinal osteoblastomas arise from the posterior elements of the spine; there have been no published reports of the tumor in the odontoid process of the axis. Accurate preoperative localization of the tumor is important for planning minimally invasive surgery on such benign tumors. However, the magnetic resonance imaging (MRI) findings may be misleading, because peritumoral changes may be confusing.
  
  
  METHODS
  We report the case of a 20-year-old man, who presented with a 4-year history of protracted left posterior neck pain. Preoperative computed tomography (CT) revealed a discrete mixed-density mass within the odontoid process. MRI showed diffusely abnormal signal intensity and enhancement both in the odontoid process and the body of the axis, including regions from which biopsy specimens were normal or had minimal inflammatory changes. Precise preoperative localization of the tumor margins using CT and biopsy allowed for successful resection of the tumor via a transoral approach with preservation of a part of the axis and the odontoid process. Consequently, stabilization of the spine was unnecessary, and the patient remained symptom-free for 3.5 years.
  
  
  CONCLUSIONS
  We reported a rare case of benign osteoblastoma of the odontoid process of the axis. The tumor was successfully resected via a transoral approach, preserving a part of the axis and the odontoid process. We have emphasized an advantage of CT over MRI for accurate localization of the tumor.
authors.affiliation: Department of Neurosurgery, Nagoya University School of Medicine, Showa, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Mori
authors.forename: M
authors.initials: M
authors.lastname: Takayasu
authors.forename: K
authors.initials: K
authors.lastname: Saito
authors.forename: Y
authors.initials: Y
authors.lastname: Seki
authors.forename: M
authors.initials: M
authors.lastname: Shibuya
authors.forename: J
authors.initials: J
authors.lastname: Yoshida
mesh_terms: D000328:Adult; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009192:Myelography; D009809:Odontoid Process / Q000473:pathology / Q000601:surgery; D018215:Osteoblastoma / Q000473:pathology / Q000601:surgery; D013125:Spinal Neoplasms / Q000473:pathology / Q000601:surgery; D014057:Tomography, X-Ray Computed