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Glossopharyngeal nerve (Cranial nerve IX)

The Glossopharyngeal nerve (Cranial nerve IX) is a mixed cranial nerve responsible for various sensory, motor, and autonomic functions. Originating from the medulla oblongata, it exits the skull via the jugular foramen. It innervates structures in the oropharynx, tongue, and carotid body, playing a crucial role in taste sensation, salivation, and cardiovascular reflexes. Its course, relations, and functions make it clinically significant, especially in the context of head and neck pathology.

Synonyms

  • Cranial Nerve IX

  • N. glossopharyngeus

  • Ninth Cranial Nerve

  • CN IX

Function

  • Sensory: Provides taste sensation from the posterior one-third of the tongue; general sensation from the pharynx, tonsils, and middle ear.

  • Motor: Supplies the stylopharyngeus muscle, facilitating swallowing.

  • Parasympathetic: Innervates the parotid gland via the otic ganglion, stimulating saliva secretion.

  • Visceral Sensory: Senses carotid body and sinus information for blood pressure and oxygen regulation.

MRI Appearance

  • T1-Weighted MRI: The glossopharyngeal nerve appears as a small, low to intermediate signal structure in the cisternal segment, located anterolateral to the vagus nerve as it exits the medulla and courses toward the jugular foramen.

  • 3D T2-Weighted MRI (CISS/FIESTA): The nerve is better visualized as a hypointense (dark) linear structure against the hyperintense (bright) background of cerebrospinal fluid. The course can be traced from the medulla through the cerebellopontine angle to the jugular foramen.

CT Appearance

  • Non-Contrast CT: The nerve itself is not directly visualized due to its small size and similar density to surrounding soft tissues.

  • CT with Contrast/High-Resolution: The glossopharyngeal nerve can be indirectly identified by its course through the pars nervosa of the jugular foramen, which appears as a small anterior compartment. Any abnormal enlargement or erosion of the jugular foramen may suggest pathology involving the nerve.

MRI images

Glossopharyngeal nerve (Cranial nerve IX) MRI 3T axial image