Nervi terminalis (“0” pair of cranial nerve) revisited from fishes to humans

Abstract

According to classical teaching in medical colleges and institutes, there are 12 pairs of cranial nerves, attached to the brain. They are numbered in Roman numerals from I to XII in the craniocaudal order of their attachment on the brain. In fact, there are 13 pairs of cranial nerves, the one which is not taught is the nervus terminalis (NT), i.e., “0” pair of cranial nerve. It is attached rostral to all other cranial nerves. Although it has been clearly identified as an additional nerve in the vertebrate species including humans for more than a century, its functional role is also understood to some extent. Still, it could not find its place in the standard textbooks of anatomy. It has also been given different names, viz., nerve of Pinkus, NT, cranial nerve “0,” cranial nerve nulla, terminal nerve, and cranial nerve XIII.