Table 2.

Grading scale for occipitoatlantal injuries [7]

Grade	Definition
I	Normal findings on CT based on established methods of diagnosis with moderately abnormal findings on MRI (high signal in posterior ligaments or occipitoatlantal joints)
II	≥1 abnormal finding on CT based on established diagnostic criteria or grossly abnormal MRI findings in occipitoatlantal joints, tectorial membrane, alar ligaments, or cruciate ligaments