Explore Online Education
Apply for Membership
Access CNS Guidelines on the CNS+ App
Visit the D.C. Press Room
CNS Annual Meeting
Join us as we count down to 2021 with a SANS question every day this month. Test your knowledge and learn something new each day as you participate. Questions will be posted to Twitter daily.
What lateral plain film measurements of the cervical spine is used to make the diagnosis of atlanto-occipital dislocation (AOD)?
BAI and BDI
The correct answer is BAI and BDI.
The basion-posterior axial line interval (BAI) is a transverse line along the posterior cortex of the axis (the posterior axial line) and the tip of the basion. The basion-dens interval (BDI) is measured from the tip of the dens to the basion.
The SANS Lifelong Learning Exams was designed to enhance medical knowledge and self-assessment in neurosurgery, reinforce practice patterns, and recognize knowledge gaps. SANS exams offer 250 questions across specialties worth up to 24 CME.
View SANS Exams
The SANS Boards app provides a convenient high-yield study resource to best prepare you for the ABNS Primary Examination.
iTunes Google Play
Tweets by CNS_Update
Contact Education Services
Find answers to frequently asked questions.