title: The Cervical Spinal Canal Tapers Differently in Patients with Chiari I with and without Syringomyelia.
abstract: OBJECTIVE
  The cause of syringomyelia in patients with Chiari I remains uncertain. Cervical spine anatomy modifies CSF velocities, flow patterns, and pressure gradients, which may affect the spinal cord. We tested the hypothesis that cervical spinal anatomy differs between Chiari I patients with and without syringomyelia.
  
  
  METHODS
  We identified consecutive patients with Chiari I at 3 institutions and divided them into groups with and without syringomyelia. Five readers measured anteroposterior cervical spinal diameters, tonsillar herniation, and syrinx dimensions on cervical MR images. Taper ratios for C1-C7, C1-C4, and C4-C7 spinal segments were calculated by linear least squares fitting to the appropriate spinal canal diameters. Mean taper ratios and tonsillar herniation for groups were compared and tested for statistical significance with a Kruskal-Wallis test. Inter- and intrareader agreement and correlations in the data were measured.
  
  
  RESULTS
  One hundred fifty patients were included, of which 49 had syringomyelia. C1-C7 taper ratios were smaller and C4-C7 taper ratios greater for patients with syringomyelia than for those without it. C1-C4 taper ratios did not differ significantly between groups. Patients with syringomyelia had, on average, greater tonsillar herniation than those without a syrinx. However, C4-C7 taper ratios were steeper, for all degrees of tonsil herniation, in patients with syringomyelia. Differences among readers did not exceed differences among patient groups.
  
  
  CONCLUSIONS
  The tapering of the lower cervical spine may contribute to the development of syringomyelia in patients with Chiari I.
authors.affiliation: From the Departments of Radiology (A.T., A.M.d.R., V.H.).
authors.forename: A
authors.identifier: http://orcid.org/0000-0002-8609-4727
authors.initials: A
authors.lastname: Thompson
authors.affiliation: Department of Radiology (N.M., G.W.), Tufts University School of Medicine, Boston, Massachusetts.
authors.forename: N
authors.identifier: http://orcid.org/0000-0002-3889-7293
authors.initials: N
authors.lastname: Madan
authors.affiliation: Department of Radiology (J.R.H.), University of California San Diego, San Diego, California.
authors.forename: J R
authors.identifier: http://orcid.org/0000-0002-6094-7365
authors.initials: JR
authors.lastname: Hesselink
authors.affiliation: Department of Radiology (N.M., G.W.), Tufts University School of Medicine, Boston, Massachusetts.
authors.forename: G
authors.identifier: http://orcid.org/0000-0003-1889-7445
authors.initials: G
authors.lastname: Weinstein
authors.affiliation: From the Departments of Radiology (A.T., A.M.d.R., V.H.) Medical Physics (A.M.d.R.), University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: A
authors.identifier: http://orcid.org/0000-0002-1743-269X
authors.initials: A
authors.lastname: Munoz del Rio
authors.affiliation: From the Departments of Radiology (A.T., A.M.d.R., V.H.) vmhaughton@wisc.edu.
authors.forename: V
authors.identifier: http://orcid.org/0000-0001-5618-4628
authors.initials: V
authors.lastname: Haughton
mesh_terms: D000328:Adult; D000375:Aging; D001139:Arnold-Chiari Malformation / Q000000981:diagnostic imaging / Q000473:pathology*; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology*; D004677:Encephalocele / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D005539:Foramen Magnum / Q000000981:diagnostic imaging / Q000473:pathology; D006547:Hernia / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D012727:Sex Characteristics; D013115:Spinal Canal / Q000000981:diagnostic imaging / Q000473:pathology*; D013131:Spine / Q000473:pathology*; D013595:Syringomyelia / Q000000981:diagnostic imaging / Q000473:pathology*