title: The Application of the Revised Condyle-C1 Interval Method to Diagnose Traumatic Atlanto-occipital Dissociation in Adults.
abstract: METHODS
  Retrospective study.
  
  
  OBJECTIVE
  Traumatic atlanto-occipital dissociation (AOD) remains a diagnostic challenge, and delay in diagnosis is associated with catastrophic outcomes. Recently, a revised version of the condyl-C1 interval (CCI) utilizing parasagittal computed tomography (CT) reconstruction was used successfully with unilateral dislocation of 2.5 mm at the level of that joint diagnostic of AOD. We report the utility of this simple technique in the diagnosis of six patients with AOD.
  
  
  METHODS
  Two blinded neurosurgeons assessed CTs of six patients with AOD and 30 patients without AOD. The following methodologies were applied: basion-dens interval (BDI), basion-axial interval (BAI), Lee X-lines, Powers ratio, CCI, and revised CCI. The average sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) as well as the kappa statistic indicating interrater reliability of each method were investigated.
  
  
  RESULTS
  The average sensitivity for BDI, BAI, Lee X-lines, Power ratio, CCI, and revised CCI was 0.75, 0.33, 0.67, 0.50, 1.00, and 1.00, respectively. The average specificity was 1.00, 1.00, 0.50, 1.00, 0.94, and 1.00, respectively. The average PPV was 1.00, 1.00, 0.25, 1.00, 0.80, and 1.00, respectively. The average NPV was 0.96, 0.88, 0.89, 0.91, 1.00, and 1.00, respectively, and the kappa statistic was 0.57, 0.25, 0.25, 0.20, 1.00, and 1.00, respectively.
  
  
  CONCLUSIONS
  Based on this study, the revised CCI method is simple yet the most sensitive and reliable technique for the diagnosis of AOD.
authors.affiliation: Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States.
authors.forename: Nader S
authors.initials: NS
authors.lastname: Dahdaleh
authors.affiliation: Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States.
authors.forename: Ryan
authors.initials: R
authors.lastname: Khanna
authors.affiliation: Department of Neurological Surgery, University of Iowa, Carver School of Medicine, Iowa City, Iowa, United States.
authors.forename: Arnold H
authors.initials: AH
authors.lastname: Menezes
authors.affiliation: Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States.
authors.forename: Zachary A
authors.initials: ZA
authors.lastname: Smith
authors.affiliation: Department of Neurological Surgery, University of Iowa, Carver School of Medicine, Iowa City, Iowa, United States.
authors.forename: Stephanus V
authors.initials: SV
authors.lastname: Viljoen
authors.affiliation: Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States.
authors.forename: Tyler R
authors.initials: TR
authors.lastname: Koski
authors.affiliation: Department of Neurological Surgery, University of Iowa, Carver School of Medicine, Iowa City, Iowa, United States.
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Hitchon
authors.affiliation: Department of Neurological Surgery, University of Iowa, Carver School of Medicine, Iowa City, Iowa, United States.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Dlouhy
keywords: atlanto-occipital dissociation; craniovertebral junction; dissociation; occipitocervical dislocation