title: Retro-odontoid pseudotumor in diffuse idiopathic skeletal hyperostosis.
abstract: METHODS
  A rare case of retro-odontoid pseudotumor combined with diffuse idiopathic skeletal hyperostosis is presented.
  
  
  OBJECTIVE
  To discuss the pathomechanism of retro-odontoid pseudotumor in diffuse idiopathic skeletal hyperostosis.
  
  
  BACKGROUND
  Reports describing craniovertebral manifestations of diffuse idiopathic skeletal hyperostosis are quite rare. Only two cases of an atlantoaxial subluxation and one case of an odontoid fracture have been reported. Myelopathy resulting from retro-odontoid pseudotumor combined with diffuse idiopathic skeletal hyperostosis has not been reported previously.
  
  
  METHODS
  A 74-year-old man presented with spastic tetraparesis caused by a retro-odontoid pseudotumor combined with diffuse idiopathic skeletal hyperostosis. Transoral removal of the extradural mass combined with a dorsal atlantoaxial fusion was performed using a titanium frame with sublaminar cable wiring.
  
  
  RESULTS
  Yellowish amorphous material extruded from between the odontoid process and the arch of C1 when the anterior capsule had been incised. The retro-odontoid mass was very firmly attached to the hypertrophied ligaments. The mass therefore had to be sharply dissected away to expose the dura. The histologic appearance of the mass consisted of poorly cell-degenerated ligament, fibrocartilage, and fibrin. There was a focal proliferation of small vessels, but no significant inflammatory component and no evidence of neoplasia. The ligaments appeared fibrillated, disintegrated, and fragmented. After surgery, the patient's neurologic function improved.
  
  
  CONCLUSIONS
  This is the first reported case of a retro-odontoid pseudotumor combined with diffuse idiopathic skeletal hyperostosis. The secondary transfer of mechanical stress to the atlantoaxial segment was presented as a pathomechanism underlying the formation of this retro-odontoid pseudotumor.
authors: St. Peter's Spine Center, Seoul, Korea, and the; Department of Surgical Neurology, The National Hospital for Neurology and Neurosurgery, London, United Kingdom. drbyjun@hotmail.com
authors: Byung-Yoon
authors: BY
authors: Jun
authors: Kang-Jun
authors: KJ
authors: Yoon
authors: Alan
authors: A
authors: Crockard
mesh_terms: D000368:Aged; D006801:Humans; D004057:Hyperostosis, Diffuse Idiopathic Skeletal / Q000473:pathology* / Q000601:surgery; D008297:Male; D009809:Odontoid Process / Q000473:pathology* / Q000601:surgery; D013122:Spinal Diseases / Q000473:pathology* / Q000601:surgery