title: Basilar Invagination: Case Report and Literature Review.
abstract: BACKGROUND
  Basilar invagination is a rare clinical condition characterized by upward protrusion of the odontoid process into the intracranial space, leading to bulbomedullary compression. It is often encountered in adults with rheumatoid arthritis. Transoral microscopic or endonasal endoscopic decompression may be pursued, with or without posterior fixation. We present a case of basilar invagination with C1-C2 autofusion and discuss an algorithm for choice of anterior versus posterior approaches.
  
  
  METHODS
  A 47-year-old woman with rheumatoid arthritis presented with severe occipital and cervical pain, dysphagia, hoarseness, and arm paresthesias. Findings on magnetic resonance imaging revealed moderate cranial settling with the odontoid indenting the ventral medulla but no posterior compression. Computed tomography demonstrated bony fusion at C1-C2 without lateral sag. Given autofusion of C1-C2 in proper occipitocervical alignment and the absence of posterior compression, the patient underwent endoscopic endonasal odontoidectomy without further posterior fusion, with satisfactory resolution of symptoms.
  
  
  CONCLUSIONS
  Endoscopic endonasal odontoidectomy offers a safe and effective method for anterior decompression of basilar invagination. Preoperative assessment for existing posterior fusion, absence of posterior compression, and preservation of the anterior C1 ring during operative decompression help stratify the need for lone anterior approach versus a combined anterior and posterior treatment.
authors.affiliation: Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Nauman S
authors.initials: NS
authors.lastname: Chaudhry
authors.affiliation: Department of Neurological Surgery, Oregon Health Sciences University, Portland, Oregon, USA.
authors.forename: Alp
authors.initials: A
authors.lastname: Ozpinar
authors.affiliation: Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Wenya Linda
authors.initials: WL
authors.lastname: Bi
authors.affiliation: Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Vamsidhar
authors.initials: V
authors.lastname: Chavakula
authors.affiliation: Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: John H
authors.initials: JH
authors.lastname: Chi
authors.affiliation: Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA. Electronic address: idunn@partners.org.
authors.forename: Ian F
authors.initials: IF
authors.lastname: Dunn
mesh_terms: D001172:Arthritis, Rheumatoid / Q000150:complications*; D019299:Decompression, Surgical; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008526:Medulla Oblongata / Q000473:pathology*; D008875:Middle Aged; D044583:Neuroendoscopy; D009666:Nose; D009809:Odontoid Process / Q000473:pathology / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
keywords: Anterior odontoid decompression; Basilar invagination; Cervicomedullary junction compression; Endoscopic endonasal odontoidectomy; Posterior odontoid decompression