Cranial Nerve Zero (CN 0): Multiple Names and Often Discounted yet Clinically Significant

Cranial nerve zero: What the rhinologist needs to know

“…As an example, the nerve has been well‐described in whales, however, whales have no CN I and no sense of smell. In humans, CN 0 appears to be tied into the hypothalamic kisspeptin (KP) neuronal network 7 . The KP neural network is involved in sexual development and human reproduction by inducing gonadotropin‐releasing hormone (GnRH) from the hypothalamus.…”

“…In humans, CN 0 appears to be tied into the hypothalamic kisspeptin (KP) neuronal network. 7 The KP neural network is involved in sexual development and human reproduction by inducing gonadotropin-releasing hormone (GnRH) from the hypothalamus. This suggests a possible pheromone function for CN 0, which has not been confirmed.…”

Smelling TNT: Trends of the Terminal Nerve

“…While some authors have reported that the nerve's origin is from the olfactory placode, where olfactory cells also originate, others indicate that it arises from the neural crest. The most widely accepted hypothesis is that, like other cranial nerves, its embryological origins lie in synergistic interactions during development between the neural crest and sensory placodes [1]. The terminalis nerve forms at the limit of migrating neural crest cells with the olfactory and adenohypophyseal placodes [4].…”

“…Initially, it was named the following: nerve of Pinkus, tractus olfacto-commissuralis, new nerve, terminal nerve, nerve nulla (i.e., nothing, zero), and cranial nerve 13. Then, it was renamed "nervus terminalis" since it entered the region of the lamina terminalis, which is the currently accepted nomenclature [1]. The Latin name nervus terminalis, which has now been replaced by the names terminal nerve and terminalis nerve (TN), refers to a rudimentary structure found in human and higher mammals, which can be found in fetal stages.…”

“…Its fibers are non-myelinated and run alongside the dura mater, passing through the subarachnoid space and ultimately connecting to the pia mater in the gyri of the frontal lobes. It enters the brain through the lamina terminalis, implying penetration into the prosencephalon [1] (Figure 1). Roussel et al have confirmed this in their work on the landmarks used during endonasal skull base surgery [5].…”