It refers to a line connecting posterior edge of the hard palate to the most caudal point of the occipital curve. If the tip of the dens lies more than 4.5 mm above this line it is indicative of basilar invagination.
- 1. Kwong Y, Rao N, Latief K. Craniometric measurements in the assessment of craniovertebral settling: are they still relevant in the age of cross-sectional imaging?. AJR Am J Roentgenol. 2011;196 (4): W421-5. doi:10.2214/AJR.10.5339 - Pubmed citation
- 2. Keats TE, Sistrom C. Atlas of Radiologic Measurement. Mosby. (2001) ISBN:0323001610. Read it at Google Books - Find it at Amazon