Anatomic Landmarks of the Glossopharyngeal Nerve: A Microsurgical Anatomic Study: In Reply

Abstract

OBJECTIVE: Compared with other lower cramal nerves, the glossopharyngeal nerve (GPhN) is well hidden within the juguiat furamen, at the infratemporal fossa, and in the deep layers of the neck. This study aims to disclose the course of the GPhN and point out landmarks to aid in its exposure. METHODS: The GPhN was studied in 10 cadaveric heads (20 sides) injected with colored latex for microsurgioal dissection The specimens were dissected under the surgical microscope. RESULTS: The GPhN can be divided into three portions, cisternal, jugular foramen, and extracranial. The roothes of the GPhN emerge from the postolivary sulcus and course ventral to the floccuius and choroid plexus of the lateral recess of the fourth ventricle. The nerve then enters the jugut foramen through the uppermost porus (pars nervosa) and is separated from the vagus and accorssory nerves by a fibrous crest. The cochlear aqueduct Opens to the roof of this porus. On foor sides in the cadaver specimens (20%), the GPhN traversed a separate bony canal within the jugular foramen; no separate canal was found in the other cadavers, in all specimens, the Jacobon's (tympanic) serve emerged from the inferior ganglion of the CPhN, and the Arnold's (auticalat brancht of the vagost nerve also consisted of branches from the GPhN. The GPhN revds from the juguiar foramen posteromedial to the styloid process and the styloiod muscles, The last four cranial nervres and the internal jugular vein pass through a narrow space between the transverse process of the altas (CT) and the styloid process. The styloid muscles are a pytamid shape, the tip of which is formed by the attachment of the styloid muscles to the styloid precess The GPhN crosses to the anterior side of the stylopharyngeus muscle at the junction of the shlopharyngeus, middle constictes, and hyoglossal muscles, which are at the base of the pyranid. The middle constrictor muscle formis a wall between the GPhN and the hypoglossal nerve in this region. Then, the GPhN gives off a lingual branch and deepens to innervate the pheryeal mucosa. CONCLUSION: Type landmarks help to identify the GPhN in the subarachnoid space, the choroid plessis of the lateral recess of the fourth ventricle and the dural entrance porus of the jugular foramen, The opening of the cochlear aqueduct, the mastoid canalicuius, and the inferior tympanic canalicultis are three landmarks of the GPhN within the jugular foramen. Finally, the base of the styloid process, the base of the styloid pyramid, and the transverse process of the atlay serve as three landmarks of the GPhN at the extracranial region in the infratemporal fossa.