Anatomical and prospective clinical study of variant distribution of the glossopharyngeal nerve

Background: Removal of lesions involving the jugular foramen region requires detailed knowledgeof the anatomy and anatomical landmarks of the related area, especially the lower cranial nerves. Theglossopharyngeal nerve (GPhN) courses along the uppermost part of the jugular foramen and is wellhidden in the deep layers of the neck, making this nerve is the most difficult one to identify duringsurgery. The glossopharyngeal nerve can be compromised iatrogenically during the surgical procedures.Aim of the work: Is to investigate the topography and branching pattern of the GPhN and to define theimportant landmarks that can help to identify this nerve during surgery. It also designed to evaluate thepost-tonsillectomy pain and the role of the different patterns of distribution of the glossopharyngeal nervebranches within the tonsillar fossa in the perception of pain in the postoperative period.Materials and Methods: Thirty glossopharyngeal nerves in fifteen cadaveric necks were dissected. Theanatomic relation between the GPhN and the nearby structures, distribution and branching pattern of theGPhN were studied. Regarding the GPhN in the tonsilar fossa two anatomic distances were measured:A) distance from the posterosuperior tonsillar fossa to the main trunk of the GPhN and B) distance fromthe posteroinferior tonsillar fossa to the closest lingual branch of the glossopharyngeal nerve (LBG). Thelevel of the post-operative pain was estimated in 70 patients at one and three hours, and one week aftertonsillectomyby numeric pain intensity scale Technique of anesthesia was similar for all patients. At theend of the procedure, a 1 ml mixture of Xylocain- Marcaine solution was infiltrated in the lower tonsillarpole on both sides.Results: The GPhN can be divided into three portions: cisternal, jugular foramen and extracranial part.Tough dural septum separates the jugular part of the GPhN from both vagus and accessory nerves in 20%of the cadaveric specimens. The GPhN was anastomosed with the hypoglossal nerve in 40% and withthe lingual nerve in 50%. The lingual branch of the glossopharygeal nerve (LBG) entered the tongueobliquely bifurcated into medial and lateral primary branches, with the former innervating most ofthe circumvallate papillae. In 30% the medial branches of LBG extended anteriorly beyond the sulcusterminalis and the circumvallate papillae. Tonsillar branches were originating from the GPhN in 60% andfrom the LBG in 40%. The mean distance from the posterosuperior tonsillar fossa and the main trunkof the glossopharyngeal nerve was 9.3 mm, and the mean distance from the posteroinferior tonsillarfossa and the closest lingual branch of the glossopharyngeal nerve was6.7 mm. Results of the clinicalstudy showed statistically significant lower pain scores (according to VAS score) in the recovery room,1and 3hours after surgery in the group that received local anesthetic infiltration compared with the othergroup that didn’t receive any local anesthetic infiltration. Also 1 week postoperatively there was again astatistically significant lower pain scores in the group that received local anesthetic infiltration.Conclusions: Accurate identification and exposure of the GPhN allow for its preservation during surgicalresection of any pathological entities along its course. The results of the anatomical dissection study donepoints to the crucial role the glossopharyngeal nerve branching patterns in determining the level of thepostoperative pain perception after tonsillectomy operation.