title: Clivus height value: a new diagnostic method for basilar invagination at CT.
abstract: OBJECTIVE
  To investigate whether clivus height (CH; the distance of the basion above Chamberlain's line) could be used to diagnose basilar invagination (BI) at computed tomography (CT).
  
  
  METHODS
  This retrospective study received institutional review board approval, and was performed from 1 January 2013, to 1 July 2015 with a waiver of informed consent. CH was measured on mid-sagittal reconstructed CT images from 65 BI patients and 85 control subjects to compare the two groups by using the independent-samples t-test. Inter- and intra-observer reliability were evaluated with the intraclass correlation coefficient (ICC). To evaluate the diagnostic performance and determine the cut-off value of CH, receiver operating characteristic (ROC) curves were utilised.
  
  
  RESULTS
  The measurement of CH showed good inter- and intra-observer agreement (ICC=0.96 and 0.98, respectively). Compared with control subjects whose mean CH value was 0.35±0.29 cm (range, -0.18 to 1.2 cm), BI patients had a significantly (p<0.001) larger CH, 1.2±0.55 cm (range, 0.43-3.2 cm). The area under the ROC curve was 0.949 (95% confidence interval: 0.916, 0.982), and based on the cut-off value of 0.65 cm, the sensitivity, specificity, positive predictive value, and negative predictive value were 0.88 (57/65), 0.88 (75/85), 0.85 (57/67), and 0.91 (75/82), respectively.
  
  
  CONCLUSIONS
  Although not better than CL (the distance of the odontoid tip above Chamberlain's line), measurement of CH at CT is reproducible and can diagnose patients with BI.
authors.affiliation: Shandong Medical Imaging Research Institute, Shandong University, Jinan, China.
authors.forename: S
authors.initials: S
authors.lastname: Xu
authors.affiliation: Shandong Medical Imaging Research Institute, Shandong University, Jinan, China. Electronic address: grzh99@126.com.
authors.forename: R
authors.initials: R
authors.lastname: Gong
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003388:Cranial Fossa, Posterior / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D015588:Observer Variation; D010985:Platybasia / Q000000981:diagnostic imaging*; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult