Cranial nerves were nerves that emerged directly from the brain.
In 2373, Kes attempted to restore Chardis' cranial nerves after he had been attacked by the Swarm species, but he ultimately died from his injuries. (VOY: "The Swarm")
In 2374, The Doctor anesthetized Seven of Nine's cranial nerves with 20 ccs of anetrizine. (VOY: "The Gift")