Diagnosis & Imaging
McGregor's line
McGregor's line is a craniometric reference line, similar to Chamberlain's, used to help assess for basilar invagination in Chiari-related evaluation.
In short: McGregor's line
- It is a reference line on imaging of the skull base.
- It runs from the hard palate to the lowest point of the occipital bone.
- It helps assess for basilar invagination.
- It is often used because its landmarks are easy to identify.
What it is
McGregor's line is a craniometric reference line used in evaluating the craniocervical junction, similar in purpose to Chamberlain's line. It is drawn from the back of the hard palate to the lowest point of the occipital bone, and it helps assess for basilar invagination.
Understanding McGregor's line
Like Chamberlain's line, McGregor's line is used to evaluate whether the odontoid process extends abnormally upward, which would suggest basilar invagination. McGregor's line is often favored because its landmarks (the hard palate and the lowest point of the occiput) are reliably identifiable on standard imaging. If the odontoid tip extends above this line by more than a defined amount, basilar invagination is suggested. This matters in Chiari because basilar invagination is among the bony abnormalities that can accompany the condition and influence treatment. McGregor's line is one of several craniometric measurements used together to assess craniocervical alignment. Understanding McGregor's line clarifies another reference line used to detect basilar invagination in evaluating Chiari.
Why it matters
Understanding McGregor's line helps families see how another easily identified reference line is used to assess for basilar invagination — relevant because it can accompany Chiari and affect treatment.
Common questions
What is McGregor's line?
A reference line from the hard palate to the lowest point of the occipital bone.
What does it help assess?
Basilar invagination.
Why is it commonly used?
Its landmarks are reliably identifiable on imaging.
Bottom line
McGregor's line is a craniometric reference line used to assess for basilar invagination, with easily identified landmarks, relevant in Chiari evaluation.
Browse all 265 Chiari malformation definitions
Read the Chiari malformation patient guides
Not sure which page you need? Put words to it with the symptom navigator