When the Air Hits Your Brain: Tales from Neurosurgery

by Frank T. Vertosick Jr.

The body has twelve pairs of cranial nerves, so named because they exit from the brain itself, not from the spinal cord. The cranial nerves mediate the sensory and motor functions of the head and neck. The first cranial nerves are the olfactory nerves, which convey the sense of smell; the second cranial nerves the optic nerves, which convey the sense of sight; and so on. The fifth cranial nerve conveys sensations from the face. It is also called the trigeminal nerve, from the Greek phrase meaning “three origins,” because the main nerve branches into three divisions: V1 (called vee-one, even though the “V” is meant to be the Roman numeral five, not the letter), which supplies sensation to the forehead and eyes; V2, which supplies the cheeks, upper teeth, and upper lip; and V3, which supplies the jaw, lower teeth, and lower lip. The trigeminal nerve is somewhat rudimentary in humans compared to the nerves of lower animals, such as mice or cats, which have whiskers and depend upon keen facial sensation for their survival.