Cranial nerve zero
|Cranial nerve zero|
|The original images (1878) of Fritsch's dogfish shark brain showing the nerve marked by an asterisk.|
|Three forms of the nerve on the underside of human brains.|
The terminal nerve, or cranial nerve zero, was discovered by German scientist Gustav Fritsch in 1878 in the brains of sharks. It was first found in humans in 1913, although its presence in humans remains controversial. However, a study has indicated that the terminal nerve is a common finding in the adult human brain. The nerve has been called by other names, including Cranial Nerve XIII, Zero Nerve, and Nerve N.
|CN 0 – Terminal|
|CN I – Olfactory|
|CN II – Optic|
|CN III – Oculomotor|
|CN IV – Trochlear|
|CN V – Trigeminal|
|CN VI – Abducens|
|CN VII – Facial|
|CN VIII – Vestibulocochlear|
|CN IX – Glossopharyngeal|
|CN X – Vagus|
|CN XI – Accessory|
|CN XII – Hypoglossal|
The terminal nerve appears just anterior of the other cranial nerves bilaterally as a microscopic plexus of unmyelinated peripheral nerve fascicles in the subarachnoid space covering the gyrus rectus. This plexus appears near the cribriform plate and travels posteriorly toward the olfactory trigone, medial olfactory gyrus, and lamina terminalis.
The nerve is often overlooked in autopsies because it is unusually thin for a cranial nerve, and is often torn out upon exposing the brain. Careful dissection is necessary to visualize the nerve. Its purpose and mechanism of function is still open to debate; consequently, nerve zero is often not mentioned in anatomy textbooks.
Although very close to (and often confused for a branch of) the olfactory nerve, nerve zero is not connected to the olfactory bulb, where smells are analyzed. This fact suggests that the nerve is either vestigial or may be related to the sensing of pheromones. This hypothesis is further supported by the fact that nerve zero projects to the medial and lateral septal nuclei and the preoptic areas, all of which are involved in regulating sexual behavior in mammals.
The connections between cranial nerve zero and the olfactory system has been extensively studied in human embryos. It was found to enter the brain at stages 17 and 18 from olfactory origins.
- R. Douglas Fields, Sex and the Secret Nerve, February/March 2007; Scientific American Mind
- Fuller GN, Burger PC (1990). "Nervus terminalis (cranial nerve zero) in the adult human". Clin. Neuropathol. 9 (6): 279–83. PMID 2286018.
- Bordoni, Bruno; Emiliano Zanier (12 March 2013). "Cranial nerves XIII and XIV: nerves in the shadows". Journal of Multidisciplinary Healthcare (6): 87–91. Retrieved 7 November 2013.
- Bordoni, Bruno and Zanier, Emiliano (2013)."Cranial nerves XIII and XIV: Nerves in the Shadows." Journal of Multidisciplinary Healthcare (3); 6 p. 87.
- Von Bartheld CS (September 2004). "The terminal nerve and its relation with extrabulbar "olfactory" projections: lessons from lampreys and lungfishes". Microsc. Res. Tech. 65 (1–2): 13–24. doi:10.1002/jemt.20095. PMID 15570592.
- Whitlock KE (2004). "Development of the nervus terminalis: origin and migration". Microsc. Res. Tech. 65 (1–2): 2–12. doi:10.1002/jemt.20094. PMID 15570589.
- Müller F, O'Rahilly R (2004). "Olfactory structures in staged human embryos". Cells Tissues Organs (Print) 178 (2): 93–116. doi:10.1159/000081720. PMID 15604533.
- Diagram at kent.edu ("nervus terminalis", #4)
-  The neglected cranial nerve: Nervus terminalis (cranial nerve N).
-  Nervus terminalis (cranial nerve zero) in the adult human.