Detailed MR Imaging Anatomy of the Cisternal Segments of the Glossopharyngeal, Vagus, and Spinal Accessory Nerves in the Posterior Fossa: The Use of 3D Balanced Fast-Field Echo MR Imaging

Axial 3D-bFFE images at the level of each compartment of the JF on the left side. The angle between each compartment and the posterior petrosal surface was visualized by a line drawing. A−C, The dotted arrow indicates CN IX (A and B) and the black arrow indicates the CN X/XI complex (C). Note that the angle of the cochlear aqueduct (A) is the smallest, whereas the angle of the recess for the CN X/XI complex (C) is the largest. The angle of the recess for CN IX (B) is between the angles of the cochlear aqueduct and the recess for the CN X/XI complex.

Axial 3D-bFFE images of the lower cranial nerves from the level of the cochlear aqueduct to the level of the lower margin of the JF on the left side. A and B, The white arrows indicate the recess for the cochlear aqueduct. C−E, Just below the level of the cochlear aqueduct, the glossopharyngeal nerve (small black arrows in C−E) is visualized in the recess for the glossopharyngeal nerve (white dotted arrow in C and D). Just inferior to the glossopharyngeal nerve, there is a dural ring seen as slightly dark signal intensity at the apex of the JF (white crossed arrow in E). F and G, Just below the level of the dural ring, the recess for the CN X/XI complex (white arrowhead) and the vagus nerve (black arrowhead) is visualized. H, The spinal accessory nerve (black arrow) is visualized in the recess for the CN X/XI complex (white arrowhead) at the level of the lower end of the JF.