EBM Consult

McRae Line on Radiographic Image


  • The McRae line is a line drawn on a lateral radiograph of the skull or on a sagittal cut from a CT or MRI scan that connects the posterior (opisthion) and anterior (basion) aspects of the foramen magnum
  • The tip of the dens (or odontoid process) should be ~5 mm below this line.  If it is above this line it is concerning for a possible basilar invagination.

McRae Line

    Radiographic Image

    McRae Line Image

      If the tip of the dens is eroded then the Redlund-Johnell and modified Ranawat methods (normal CT values for men is > 23.7 mm and for women is > 24.2 mm)

    Related Content

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    Chamberlain Line  Wackenheim Line   Lateral X-Ray      Odontoid View

    1. Kwong Y et al.  AJR Am J Roentgenol 2011;196(4):W421-5. PubMed 
    2. Cronin CG et al.  Clin Radiol 2009;64(1):64-9. PubMed 
    Editors & Reviewers

    Editors:  Anthony J. Busti, MD, PharmD, FNLA, FAHA
    Last Updated: June 2015