title: Retro-odontoid synovial cyst resected via an anterolateral approach without fusion.
abstract: OBJECTIVE
  Retro-odontoid synovial cysts are rare and attributable to degenerative changes in the atlantoaxial joints. An anterolateral approach facilitates access to lesions located anterior to the craniocervical junction without harming the atlantoaxial joints, and can also treat small lesions in the ventral mid-portion of the craniocervical junction without compression of spinal cord.
  
  
  METHODS
  We present herein the case of a 70-year-old man with a retro-odontoid synovial cyst. A ventral midsection mass was present at the level of the atlantoaxial joint. The compressed anterior medulla led to neurological deficits. Slight atlantoaxial instability was radiologically present. An intradural cyst resection without fusion was performed via the anterolateral approach. The diagnosis of a synovial cyst was histologically confirmed.
  
  
  RESULTS
  The patient was followed up for 3 years and exhibited improvements in the neurological deficits. There were no recurrence and postoperative deterioration of atlantoaxial instability.
  
  
  CONCLUSIONS
  The anterolateral approach for the retro-odontoid synovial cyst had little effect on C1-2 instability and yielded neurological improvements.
authors.affiliation: Department of Neurosurgery, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan, ohnishi@nsurg.med.osaka-u.ac.jp.
authors.forename: Yu-Ichiro
authors.initials: Y
authors.lastname: Ohnishi
authors.forename: Koichi
authors.initials: K
authors.lastname: Iwatsuki
authors.forename: Shigenori
authors.initials: S
authors.lastname: Taketsuna
authors.forename: Koshi
authors.initials: K
authors.lastname: Ninomiya
authors.forename: Toshiki
authors.initials: T
authors.lastname: Yoshimine
mesh_terms: D000368:Aged; D001268:Atlanto-Axial Joint; D006801:Humans; D008297:Male; D009809:Odontoid Process; D019637:Orthopedic Procedures / Q000379:methods*; D013581:Synovial Cyst / Q000175:diagnosis / Q000601:surgery*