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.

BACKGROUND AND PURPOSE: The cisternal segments of the lower cranial nerves (CNs) adjacent to the jugular foramen (JF) are difficult to identify reliably by routine MR imaging. We performed a 3D balanced fast-field echo imaging technique (3D-bFFE) to obtain detailed anatomy of the cisternal segments of CNs IX, X, and XI.

MATERIALS AND METHODS: 3D-bFFE was used to image the cisternal segments of the lower CNs in 20 healthy volunteers. As an anatomic landmark, CSF recesses adjacent to the JF were divided into 3 parts: the recess for the cochlear aqueduct, the recess for CN IX, and the recess for the CN X/XI complex. MR images were evaluated to identify the cisternal segment of each cranial nerve in relation to these anatomic landmarks.

RESULTS: The mean angles of the recess for the cochlear aqueduct for CN IX and CN X/XI to the posterior petrous bone were 41.6 +/- 2.5 degrees , 69.7 +/- 3.1 degrees , and 76.0 +/- 3.4 degrees , respectively (P < .01). The mean length of the recess for the cochlear aqueduct for CN IX and the CN X/XI complex was 5.91 +/- 0.19, 5.08 +/- 0.11, and 4.76 +/- 0.13 cm, respectively (P < .01). 3D-bFFE adequately depicted the cisternal segments of CN IX on 38 sides (95%) and the CN X/XI complex on 39 sides (97.5%).

CONCLUSIONS: The cisternal segments of CN IX, CN X, and CN XI are well identified by using 3D-bFFE, especially by determining the angles of the CSF recesses adjacent to the JF.