Trigeminal nerve fibers have passed medially through the middle cerebellar peduncle to reach the region of the sensory (and motor) nuclei associated with this nerve. Some of the sensory fibers will turn caudally and descend in the spinal tract of the trigeminal nerve. Others will terminate at this level, in the chief sensory nucleus, or the rostral tip of the nucleus of the spinal tract. Both nuclei contribute fibers to the pathway that crosses the midline and ascends as the ventral secondary trigeminal tract.