Cranial Pair 0: The Nervus Terminalis

Abstract

Originally discovered in elasmobranchs by Fritsh in 1878, the nervus terminalis has been found in virtually all species, including humans. After more than one-century debate on its nomenclature, it is nowadays recognized as cranial pair zero. The nerve mostly originates in the olfactory placode, although neural crest contribution has been also proposed. Developmentally, the nervus terminalis is clearly observed in human embryos; subsequently, during the fetal period loses some of its ganglion cells, and it is less recognizable in adults. Fibers originating in the nasal cavity passes into the cranium through the middle area of the cribiform plate of the ethmoid bone. Intracranially, fibers joint the telencephalon at several sites including the olfactory trigone and the primordium of the hippocampus to reach preoptic and precommissural regions. The nervus terminalis shows ganglion cells, that sometimes form clusters, normally one or two located at the base of the crista galli, the so-called ganglion of the nervus terminalis. Its function is uncertain. It has been described that its fibers facilitates migration of luteinizing hormone-releasing hormone cells to the hypothalamus thus participating in the development of the hypothalamic-gonadal axis, which alteration may provoke Kallmann's syndrome in humans. This review summarizes current knowledge on this structure, incorporating original illustrations of the nerve at different developmental stages, and focuses on its anatomical and clinical relevance. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc.

Nervus terminalis and nerves to the vomeronasal organ: a study using human fetal specimens

“…However, in rabbit fetuses, a number of ganglion cells on the crista galli seemed to contain almost 10% of terminalis nerve neurons [23]. Recently, Peňa-Melian et al (2019) [24] described the VNON and terminal nerve containing ganglion cell bodies along the crista galli in a human fetus of 76 mm CRL, but we were difficult to identify them in their lower magnification photo.…”

Cranial Nerves: Mind Your Head

“…This Special Issue of The Anatomical Record compiles works in the above mentioned Ontogeny/Phylogeny and Morphology/Clinical Significance topics. The organizational/developmental point of view (Volume 1 of this Special Issue) is populated with the long debated cranial par 0 or nervus terminalis (Peña‐Melián et al ., ), the very atypical and interesting features of the olfactory nerve (Crespo et al ., ), the development and pathologies of optic nerves (Herrera et al ., ), the organization and function of the oculomotor complex in different vertebrate brains, and the complex evolutionary relationships derived from the comparative analysis of eye muscles innervation (Company et al ., ; Ferran and Puelles, ), the anatomy and physiology of the auditory portion of the VIIIth nerve and the segmental organization of vestibular complex afferents and efferents (Carricondo and Romero‐Gómez, ; Diaz and Puelles, ), the atypical features of the spinal accesory motor neurons and the present neuromeric brainstem conception (prosomeric model) after new data from the visceral cranial nerve efferents (Puelles et al ., ; Watson and Tvrdik, ), and characterization of the cranial nerves in lampreys (Pombal and Megías, ). This volume 1 Ontogeny/Phylogeny of the Cranial Nerves Special Issue is completed with a historical overview of the cranial nerves (Porras et al ., ).…”

Cranial Nerves: Phylogeny and Ontogeny

“…The phylogeny and ontogeny volume includes an historical review (Porras‐Gallo et al, ), a review from a segmental perspective (Puelles et al, ), two comparative contributions on amphioxi (Ferran and Puelles, ) and lampreys (Pombal and Megías, ), and articles devoted to cranial nerves zero (Peña‐Melián et al, ), I (Crespo et al, ), II (Herrera et al, ), III, IV and VI (Company et al, ), VIII cochlear (Carricondo and Romero‐Gómez, ) and vestibular (Diaz and Puelles, ), and XI (Watson and Tvrdik, ).…”

“…The controversial cranial nerve zero or nervus terminalis has also been reviewed by Peña‐Melián et al (), who discuss it from ontogenetic, phylogenetic, anatomical, and clinical perspectives. This nerve is identifiable in embryos but not in adults.…”