Tracking the glossopharyngeal nerve pathway through anatomical references in cross-sectional imaging techniques: a pictorial review.

The glossopharyngeal nerve (GPN) is a rarely considered cranial nerve in imaging interpretation, mainly because clinical signs may remain unnoticed, but also due to its complex anatomy and inconspicuousness in conventional cross-sectional imaging. In this pictorial review, we aim to conduct a comprehensive review of the GPN anatomy from its origin in the central nervous system to peripheral target organs. Because the nerve cannot be visualised with conventional imaging examinations for most of its course, we will focus on the most relevant anatomical references along the entire GPN pathway, which will be divided into the brain stem, cisternal, cranial base (to which we will add the parasympathetic pathway leaving the main trunk of the GPN at the cranial base) and cervical segments. For that purpose, we will take advantage of cadaveric slices and dissections, our own developed drawings and schemes, and computed tomography (CT) and magnetic resonance imaging (MRI) cross-sectional images from our hospital's radiological information system and picture and archiving communication system. TEACHING POINTS: • The glossopharyngeal nerve is one of the most hidden cranial nerves. • It conveys sensory, visceral, taste, parasympathetic and motor information. • Radiologists' knowledge must go beyond the limitations of conventional imaging techniques. • The nerve's pathway involves the brain stem, cisternal, skull base and cervical segments. • Systematising anatomical references will help with nerve pathway tracking.