Magnified View of Left Cranial Nerves IX-XII Entering their foramina. The jugular foramen is a space between the petrous temporal bone anteriorly and the occipital bone posteriorly. It is divided into two unequal compartments by a fibroosseous bridge. The smaller, anteromedial compartment is the pars nervosa, which transmits the glossopharyngeal (CNIX) nerve and the inferior petrosal sinus. The larger, posterolateral compartment is the pars vascularis. It contains the jugular bulb and transmits the vagus (CNX) and both and spinal portions the spinal accessory (CNXI) . The hypoglossal (CNXII) nerve is shown leaving the medulla and converging on the hypoglossal canal. The posterior inferior cerebellar artery, the largest branch the vertebral artery, passes posteriorly around the upper part the medulla between the origins the vagus and spinal accessory to supply the under surface the cerebellum. (Image courtesy M Nunez)