title: The rise and fall of the craniocervical junction relative to the hard palate: a lifetime story.
abstract: OBJECTIVE
  Endoscopic approaches to the anterior craniocervical junction are increasing in frequency. Choice of oral versus endoscopic endonasal approach to the odontoid often depends on the relationship of the C1-2 complex to the hard palate. However, it is not known how this relevant anatomy changes with age. We hypothesize that there is a dynamic relationship of C-2 and the hard palate, which changes with age, and potentially affects the choice of surgical approach. The aim of this study was to characterize the relationship of C-2 relative to the hard palate with respect to age and sex.
  
  
  METHODS
  Emergency department billing and trauma records from 2008 to 2014 were reviewed for patients of all ages who underwent cervical or maxillofacial CT as part of a trauma evaluation for closed head injury. Patients who had a CT scan that allowed adequate visualization of the hard palate, opisthion, and upper cervical spine (C-1 and C-2) were included. Patients who had cervical or displaced facial/skull base fractures, a history of rheumatoid arthritis, or craniofacial anomalies were excluded. The distance from McGregor's palatooccipital line to the midpoint of the inferior endplate of C-2 (McL-C2) was measured on midsagittal CT scans. Patients were grouped by decile of age and by sex. A 1-way ANOVA was performed with each respective grouping.
  
  
  RESULTS
  Ultimately, 483 patients (29% female) were included. The mean age was 46 ± 24 years. The majority of patients studied were in the 2nd through 8th decades of life (85%). Significant variation was found between McL-C2 and decile of age (p < 0.001) and sex (p < 0.001). The mean McL-C2 was 27 mm in the 1st decade of life compared with the population mean of 37 mm. The mean McL-C2 was also noted to be smaller in females (mean difference 4.8 mm, p < 0.0001). Both decile of age (p = 0.0009) and sex (p < 0.0001) were independently correlated with McL-C2 on multivariate analysis.
  
  
  CONCLUSIONS
  The relationship of C-2 and the hard palate significantly varies with respect to age and sex, descending relative to the hard palate a full centimeter on average in adulthood. These findings may have relevance in determining optimal surgical approaches for addressing pathology involving the anterior craniocervical junction.
authors.affiliation: Department of 1 Neurological Surgery.
authors.forename: Grant W
authors.initials: GW
authors.lastname: Mallory
authors.affiliation: Orthopedics.
authors.forename: Grigoriy
authors.initials: G
authors.lastname: Arutyunyan
authors.affiliation: Department of 1 Neurological Surgery.
authors.forename: Meghan E
authors.initials: ME
authors.lastname: Murphy
authors.affiliation: Otolaryngology, and.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Van Abel
authors.affiliation: Orthopedics.
authors.forename: Elvis
authors.initials: E
authors.lastname: Francois
authors.affiliation: Department of 1 Neurological Surgery.
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Wetjen
authors.affiliation: Department of 1 Neurological Surgery.
authors.forename: Jeremy L
authors.initials: JL
authors.lastname: Fogelson
authors.affiliation: Otolaryngology, and.
authors.forename: Erin K
authors.initials: EK
authors.lastname: O'Brien
authors.affiliation: Department of 1 Neurological Surgery.
authors.forename: Michelle J
authors.initials: MJ
authors.lastname: Clarke
authors.affiliation: Radiology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Laurence J
authors.initials: LJ
authors.lastname: Eckel
authors.affiliation: Department of 1 Neurological Surgery.|Otolaryngology, and.
authors.forename: Jamie J
authors.initials: JJ
authors.lastname: Van Gompel
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001268:Atlanto-Axial Joint / Q000601:surgery*; D002574:Cervical Vertebrae / Q000601:surgery*; D019299:Decompression, Surgical / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000601:surgery*; D019635:Neurosurgical Procedures / Q000379:methods; D009809:Odontoid Process / Q000601:surgery*; D021362:Palate, Hard / Q000601:surgery*; D012737:Sex Factors; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome; D055815:Young Adult
keywords: C-1; C-2; EN = endoscopic transnasal; EO = endoscopic transoral;; McL–C2 = distance from McGregor's palatooccipital line to the midpoint of the inferior endplate of C-2; anatomy; cervical; cervicomedullary junction; craniocervical; endoscopic approaches