McGregor Line on Radiographic Image
- The McGregor line is used when the opisthion (posterior aspect of the foramen magnum) cannot be identified on a plain radiograph in an attempt to draw the Chamberlain line. The line can also be used on CT scan and MRI.
- It is made be drawing a line that connects the
posterior edge of the hard palate to the most caudal portion of the occipital
- If the tip of the dens (odontoid process) extends more than 4.5 mm above this line it is concerning for a basilar invagination.