The Cranial Nerve 0 (nervus terminalis) in Adult Humans

Introduction: Cranial nerve 0 (nervus terminalis) was identified in adult humans in 1914 medial to the olfactory nerve (CN1) and has been hypothesised to be responsive to pheromones, therefore playing a role in reproductive behaviour. Animal studies revealed the presence of GnRH neurons in the nerve, which is genetically different from the GnRH neurones of the hypothalamus, suggesting a neuromodulatory role in reproductive function. However, there has been much debate about its presence in humans. Methods and Materials: We examined 11 formalin-fixed cadaveric brains using gross and histological techniques to try to identify the nervus terminalis. Results: We found that fibre-like structures were identified on visual examination using a surgical microscope. In addition, approximately 830 Masson’s trichrome stained sections were examined, taken from the base of the frontal lobes, adjacent and separate to the olfactory nerve. We found fibres adjacent to the olfactory nerve which, although not definitive of the presence of a nervus terminalis, could suggest an anastomosis between the olfactory nerve and a possible nervus terminalis. Discussion/Conclusions: It has been shown that in toothed whales the olfactory nerve disappears and the nervus terminalis persists. It could be hypothesised that a nervus terminalis could be an extension of the olfactory nerve and could be considered when discussing human pheromone responses. Elzbieta Czernichowska will be the presenting author and is in her fourth (final) year of the BSc (Hons) Anatomy degree programme at the University of Glasgo