From the Guidelines
The Glossopharyngeal nerve (CN IX) is responsible for various functions, including branchial motor innervation to the stylopharyngeus muscle, visceral motor parasympathetic innervation to the parotid gland, visceral sensory innervation to the carotid sinus, and general and special sensory innervation to the posterior tongue [ 1, 1].
Key Functions of the Glossopharyngeal Nerve
- Motor functions: The glossopharyngeal nerve provides motor innervation to the stylopharyngeus muscle, which elevates the palate [ 1, 1].
- Parasympathetic functions: The nerve provides visceral motor parasympathetic innervation to the parotid gland [ 1, 1].
- Sensory functions: The glossopharyngeal nerve provides visceral sensory innervation to the carotid sinus, which plays a role in regulating circulation, and general and special sensory innervation to the posterior tongue [ 1].
- Other functions: The nerve also plays a role in swallowing and taste sensation [ 1].
Clinical Significance
Lesions or damage to the glossopharyngeal nerve can result in various symptoms, including dysphagia, ipsilateral sensory loss on the pharynx and posterior tongue, loss of gag reflex, and impaired taste [ 1, 1]. Glossopharyngeal neuralgia is a condition characterized by severe pain in the oropharyngeal and otic regions, often triggered by swallowing [ 1].
From the Research
Function of the Glossopharyngeal Nerve
The glossopharyngeal nerve (cranial nerve IX) has multiple functions, including:
- Conveying sensory, visceral, taste, parasympathetic, and motor information 2
- Mediating taste, salivation, and swallowing 3
- Containing sensory, gustatory, motor, and autonomous fibers (parasympathetic) 4
- Having mainly visceral afferent fibers from the tongue and pharynx, gustatory fibers from the posterior third of the tongue, parasympathetic afferent fibers from carotid sinus and carotid glomus, parasympathetic efferent fibers for the parotid gland, and motor fibers for the muscles of the pharynx 4
Anatomical Pathway
The glossopharyngeal nerve's pathway involves:
- The brain stem, cisternal, skull base, and cervical segments 2
- Emerging from the postolivary sulcus and coursing ventral to the flocculus and choroid plexus of the lateral recess of the fourth ventricle 5
- Entering the jugular foramen through the uppermost porus (pars nervosa) and being separated from the vagus and accessory nerves by a fibrous crest 5
- Exiting from the jugular foramen posteromedial to the styloid process and the styloid muscles 5
Clinical Significance
The glossopharyngeal nerve is important in various clinical contexts, including:
- Dysphagia, dysphonia, and autonomic parasympathetic dysfunction 6
- Neurophysiological assessment of swallowing function, laryngeal electromyogram, and heart rate variability 6
- Surgical procedures, where comprehensive knowledge of the anatomy of the glossopharyngeal nerve is crucial to avoid significant complications 3