Fig. 2

Anatomical location of the trigeminal nerve branches that innervate the nasal cavity. The schematics show sagittal views of a the nasal cavity and anterior cranial fossa (ACF), and b the nasal cavity with a reflected view of the nasal septum. The olfactory nerve and bulb are shown in green, whereas trigeminal nerve branches are blue. The region of the nasal mucosa in which the cell bodies of olfactory sensory neurons are localised is termed the olfactory epithelium (dotted line). The highly branched olfactory nerve (green) extends from the olfactory epithelium at the roof of the nasal cavity to the olfactory bulb in the anterior cranial fossa. The nasal mucosa is innervated by the nasal branches of the ophthalmic (V1) and maxillary (V2) divisions of the trigeminal nerve (blue). V1 innervates the roof and anterior aspect of the nasal cavity (to the left in both a and b), and V2 innervates the posterior and lateral aspects of the nasal cavity (to the right in a/b). The trigeminal fibers are found throughout the epithelium, also interspersed with olfactory nerve fascicles, and convey sensory information (chemosensory, nociceptive, touch, temperature) to the brainstem. The V1 branch innervating the nasal cavity is the anterior ethmoidal nerve ((1) in a). The anterior ethmoidal nerve passes closely by the olfactory bulb in the anterior cranial fossa, and gives rise to the external (2) and internal nasal nerves (medial and lateral branches, shown in b only). The V2 branches which innervate the nasal cavity are the lateral nasal nerve (posterior superior and posterior inferior branches, (4) and (5), respectively) and the nasopalatine nerve (shown in b only). Due to the close proximity of these trigeminal branches with the olfactory nerve/bulb, it is very difficult to distinguish between OEC tumours and schwannomas which arise from, to date, immunologically indistinguishable cells