title: Atlanto-occipital Instability Following Endoscopic Endonasal Approach for Lower Clival Lesions: Experience With 212 Cases.
abstract: BACKGROUND
  The endoscopic endonasal approach (EEA) for craniocervical lesions involving the lower clivus and occipital condyles carries an unclear risk of atlanto-occipital (AO) instability requiring arthrodesis.
  
  
  OBJECTIVE
  Elucidate risk factors for AO instability following EEA for clival lesions.
  
  
  METHODS
  We reviewed patients with clival tumors who underwent EEA at our institution between 2002 and 2012. Resection of the lower clivus, foramen magnum, AO joint, and occipital condyles were evaluated on fine-cut postoperative computed tomography.
  
  
  RESULTS
  Two hundred twelve patients (mean age 47.9 years, 57.1% male) underwent transclival EEA for lower clival lesions. In addition to the lower clivus, resection involved the condyle in 14.2% of patients, the foramen magnum in 16.5%, and the AO joint in 1.4%. Quantification of condyle resection revealed complete resection in 3 cases, 75% resection in 8 cases, 50% resection in 6 cases, and 25% resection in 13 cases. Seven of these patients had EEA combined with an open, far-lateral approach. In total, 7 patients required arthrodesis following EEA (3.3%), 4 of them after a combined approach. All patients who underwent arthrodesis had primary bone tumors such as chordoma, chondrosarcoma, or osteosarcoma (P = .022). Degree of condyle resection was a significant factor predisposing to occipitocervical instability (P = .001 and P < .001 for 75% and 100% condyle resection, respectively). Use of a combined approach was significantly associated with arthrodesis (P < .001).
  
  
  CONCLUSIONS
  EEA resection of the occipital condyles that results in greater than 75% condyle resection or EEA in combination with an open approach significantly increases the risk of AO instability and likely necessitates AO fixation.
  
  
  BACKGROUND
  AO, atlanto-occipitalEEA, endoscopic endonasal approachOC, occipitocervical.
authors.affiliation: *Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; ‡University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; §Department of Neurosurgery, University of Louisville, Louisville, Kentucky; ¶Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors.forename: Ali
authors.initials: A
authors.lastname: Kooshkabadi
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Choi
authors.forename: Maria
authors.initials: M
authors.lastname: Koutourousiou
authors.forename: Carl H
authors.initials: CH
authors.lastname: Snyderman
authors.forename: Eric W
authors.initials: EW
authors.lastname: Wang
authors.forename: Juan C
authors.initials: JC
authors.lastname: Fernandez-Miranda
authors.forename: Paul A
authors.initials: PA
authors.lastname: Gardner
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001174:Arthrodesis; D001269:Atlanto-Occipital Joint; D002648:Child; D002675:Child, Preschool; D003388:Cranial Fossa, Posterior / Q000601:surgery*; D005260:Female; D005539:Foramen Magnum / Q000601:surgery*; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis* / Q000209:etiology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D057605:Natural Orifice Endoscopic Surgery / Q000009:adverse effects*; D012189:Retrospective Studies; D019292:Skull Base Neoplasms / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D055815:Young Adult