title: Odontoid process and clival regeneration with Chiari malformation worsening after transoral decompression: an unexpected and previously unreported cause of "accordion phenomenon".
abstract: OBJECTIVE
  Transoral odontoidectomy followed by occipito-cervical fixation is a widely used approach to relieve ventral compressions at the craniovertebral junction (CVJ). Despite the large amount of literature on this approach and its complications, no previous reports of odontoid process and clival regeneration following transoral odontoidectomy are present in the English literature.
  
  
  METHODS
  We report the case of odontoid process and clival regeneration following transoral odontoidectomy.
  
  
  RESULTS
  A 7-year-old boy presented with symptoms of brainstem and upper cervical spinal cord compression due to a complex malformation at the CVJ including a basilar invagination with Chiari malformation. A successful transoral microsurgical endoscopic-assisted odontoidectomy extended to the clivus was performed along with occipito cervical instrumentation and fusion. Clinical and radiological resolution of the CVJ compression was evident up to 2 years post-op, when the child had a relapse of some of the presenting symptoms and the follow-up CT and MRI scans showed a quite complete regrowth of the odontoid process, clival partial regeneration and recurrence of preoperative Chiari malformation.
  
  
  CONCLUSIONS
  Besides the need of an accurate complete resection of the periosteum, which apparently was incompletely performed in our case, our experience suggests the need of resection of the odontoid down to the dentocentral synchondrosis and an accurate lateral removal of the bone surrounding the anterior tubercle of the Clivus is advised when an anterior CVJ decompression is required in children presenting a still evident synchondrosis at neuroradiological investigation.
authors.affiliation: Institute of Neurosurgery, Policlinico Gemelli, Catholic University School of Medicine, Largo A. Gemelli 8, 00168, Rome, Italy, massimiliano.visocchi@rm.unicatt.it.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Visocchi
authors.forename: Gianluca
authors.initials: G
authors.lastname: Trevisi
authors.forename: Domenico Gerardo
authors.initials: DG
authors.lastname: Iacopino
authors.forename: Gianpiero
authors.initials: G
authors.lastname: Tamburrini
authors.forename: Massimo
authors.initials: M
authors.lastname: Caldarelli
authors.forename: Giuseppe M V
authors.initials: GM
authors.lastname: Barbagallo
mesh_terms: D001139:Arnold-Chiari Malformation / Q000150:complications / Q000601:surgery*; D001861:Bone Regeneration; D002648:Child; D003388:Cranial Fossa, Posterior / Q000503:physiopathology / Q000601:surgery*; D019299:Decompression, Surgical / Q000379:methods*; D006801:Humans; D008297:Male; D009809:Odontoid Process / Q000503:physiopathology / Q000601:surgery*; D019637:Orthopedic Procedures / Q000379:methods*; D012008:Recurrence; D013117:Spinal Cord Compression / Q000209:etiology / Q000601:surgery*