Figure 46: The Course of the 6th (VI) Nerve

The sixth nucleus is located dorsally, adjacent to the 4th ventricle, in the lower pons. The genu of the facial (7th) nerve wraps around the 6th nucleus, creating the facial colliculus, which bulges into the 4th ventricle. After the 6th nerve leaves the pons, it follows a vertical course along the clivus and then to the petrous apex where is penetrates the dura, passing under the petroclinoid (Gruber's) ligament in Dorello's canal, where is it tethered and particularly susceptible to low or elevated intracranial pressure states. It then enters the cavernous sinus (adjacent to the sympathetic plexus which surrounds the internal carotid artery), travels through the superior orbital fissure to enter the orbit, and then passes through the annulus of Zinn to finally innervate the ipsilateral lateral rectus muscle.