MAGNETIC-RESONANCE-IMAGING OF CRANIAL NERVE-IX, NERVE-X, NERVE-XI, AND NERVE-XII

Cranial nerves IX (glossopharyngeal), X (vagus), and XI (spinal access ory) are intimately related. Therefore, for imaging purposes they are best considered as a unit rather than as individual structures. The XI th nerves are not considered true cranial nerves because they are form ed by cephalic (bulbar) and caudal (spinal) divisions. The XIIth (hypo glossal) nerves arise inferiorly to the above mentioned cranial nerves and exit the skull via a different set of foramina. Because the cours e of these four pairs of cranial nerves extends from the base of the s kull to the upper thorax, a combination of both magnetic resonance ima ging (MRI) and computed tomography is needed for optimal evaluation. T his article will emphasize the use of MRI when appropriate.