"The digastric line is drawn between right and left digastric grooves, which are located medial to the mastoid apices. These are considered constant in relative position. The distance from this digastric line to either the tip of the dens or a line bisecting the atlanto-occiptal joints has been described as between 11 mm and 10-12 mm, respectively. A measured distance below these thresholds may suggest basilar invagination."
"The digastric line is drawn between right and left digastric grooves, which are located medial to the mastoid apices. These are considered constant in relative position. The distance from this digastric line to either the tip of the dens or a line bisecting the atlanto-occiptal joints has been described as between 11 mm and 10-12 mm, respectively. A measured distance below these thresholds may suggest basilar invagination."
"Chamberlain's line"
"Chamberlain's line"
"McRae line"
"McGregor line"
"Bimastoid line"