ABSTRACT
The nervus terminalis, or terminal nerve, is a plexiform, ganglionated cranial nerve of unknown function found in the nose of most, if not all, vertebrates, including humans. Located rostral to the 12 cranial nerves and discovered after they were named, it is also called the zeroeth cranial nerve. In most vertebrates, the nervus terminalis shares a common origin with the vomeronasal nerve in the epithelium of the medial olfactory pit, which gives rise to the vomeronasal organ. The peripheral part of the nervus terminalis, in the form of a loose plexus, crosses the nasal mucosa and courses through the cribriform plate of the ethmoid bone medial to the olfactory and vomeronasal nerves (Fig. 1). It can be distinguished from these nerves by the presence of ganglia at nodal points in the nerve plexus and ganglion cells intermingled among the nerve fibers along its course. The intracranial part of the nervus terminalis lies along the ventromedial surfaces of the olfactory bulbs. The central part, consisting of three or four fine rootlets, enters the forebrain caudal to the medial sides of the olfactory bulbs.
