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

Background: Removal of lesions involving the jugular foramen region requires detailed knowledge
of the anatomy and anatomical landmarks of the related area, especially the lower cranial nerves. The
glossopharyngeal nerve (GPhN) courses along the uppermost part of the jugular foramen and is well
hidden in the deep layers of the neck, making this nerve is the most difficult one to identify during
surgery. 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 the
important landmarks that can help to identify this nerve during surgery. It also designed to evaluate the
post-tonsillectomy pain and the role of the different patterns of distribution of the glossopharyngeal nerve
branches 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. The
anatomic relation between the GPhN and the nearby structures, distribution and branching pattern of the
GPhN 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 from
the posteroinferior tonsillar fossa to the closest lingual branch of the glossopharyngeal nerve (LBG). The
level of the post-operative pain was estimated in 70 patients at one and three hours, and one week aftertonsillectomy
by numeric pain intensity scale Technique of anesthesia was similar for all patients. At the
end of the procedure, a 1 ml mixture of Xylocain- Marcaine solution was infiltrated in the lower tonsillar
pole 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 with
the lingual nerve in 50%. The lingual branch of the glossopharygeal nerve (LBG) entered the tongue
obliquely bifurcated into medial and lateral primary branches, with the former innervating most of
the circumvallate papillae. In 30% the medial branches of LBG extended anteriorly beyond the sulcus
terminalis and the circumvallate papillae. Tonsillar branches were originating from the GPhN in 60% and
from the LBG in 40%. The mean distance from the posterosuperior tonsillar fossa and the main trunk
of the glossopharyngeal nerve was 9.3 mm, and the mean distance from the posteroinferior tonsillar
fossa and the closest lingual branch of the glossopharyngeal nerve was6.7 mm. Results of the clinical
study 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 other
group that didn’t receive any local anesthetic infiltration. Also 1 week postoperatively there was again a
statistically 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 surgical
resection of any pathological entities along its course. The results of the anatomical dissection study done
points to the crucial role the glossopharyngeal nerve branching patterns in determining the level of the
postoperative pain perception after tonsillectomy operation.