The McGregor line connects the posterior border of the hard palate with the most caudally located point of the occiput1.
Interpretation
The dens axis should not exceed this line by more than 4.5 mm2. On MRI3 and CT4 images, the dens axis is on average 0.8 (± 2.4) mm above this line.
Imaging
References
McGregor J. The Significance of Certain Measurements of the Skull in the Diagnosis of Basilar Impression. Br J Radiol. 1948;21:171-181 ↩ ↩
Imaging and Diagnostics. In: Greenberg M, ed. Handbook of Neurosurgery. 9th Edition. Thieme; 2019. ↩ ↩
Cronin CG, Lohan DG, Mhuircheartigh J N, et al. MRI evaluation and measurement of the normal odontoid peg position. Clin Radiol. 2007;62:897-903. ↩ ↩
Cronin CG, Lohan DG, Mhuircheartigh J N, et al. CT evaluation of Chamberlains, McGregors, and McRaes skull-base lines. Clin Radiol. 2009;64:64-69. ↩ ↩