Purpose: The purpose of our study is to compare cadaver dissections with in vivo diffusion tensor imaging (DTI) to determine the position of the cervicomedullary junction (CMJ) relative to the readily identified anatomic landmarks, namely the obex and olivary bodies (olives), in normal subjects. The information gained from this study would allow further investigation into abnormalities of the CMJ, such as Chiari malformation, without the need for time-intensive tractography studies.
Methods: Six formalin-fixed human cadaver brains were compared with DTI studies in 15 normal controls. Measurements were made from the upper border of the crossing fibers of the pyramidal decussation to both the obex and the inferior margin of the olive.
Results: For the cadaver specimens, the average distance from the inferior border of the olive to the upper border of the decussation measured 3.7 mm (±1.2 mm). The average distance from the obex to the upper decussation was 6.7 mm (±2.1 mm). In the DTI subjects, the inferior olive to the upper decussation averaged 3.4 mm (±0.9 mm). The distance from the obex to the decussation averaged 6.4 mm (±1.3 mm).
Conclusion: The CMJ reliably lies 3.4 mm (±0.9 mm) caudal to the inferior border of the olive and 6.4 mm (±1.3 mm) caudal to the obex. Awareness of this anatomic relationship readily allows recognition of abnormalities of the position of the CMJ with routine imaging.