Glossopharyngeal Nerve

Original Editor - Kehinde Fatola
Top Contributors - Kehinde Fatola

Description[edit | edit source]

The glossopharyngeal nerve (Cranial Nerve IX) is a mixed nerve which transmits both motor (efferent) and sensory (afferent) impulses with contribution from four nuclei – a pair of motor and sensory nuclei each, in the medulla oblongata. [1]

Course and distribution of the glossopharyngeal, vagus, and accessory nerves..gif

Course[edit | edit source]

The glossopharyngeal nerve appears from the lateral part of the medulla oblongata and runs anterolaterally to exit the brainbox through the ventral aspect of the jugular foramen, where the sensory superior and inferior ganglia of the nerve are located. The nerve follows the stylopharyngeus muscle, being the only muscle it supplies, runs between the superior and middle pharyngeal constrictor muscles to reach the oropharynx and tongue, and contributing sensory innervation to the pharyngeal plexus of nerves. [2]

Function[edit | edit source]

The glossopharyngeal nerve has somatic motor, visceral motor, general somatic sensory, and special sensory (taste) functions.

Somatic Motor; Efferent fibres innervate the stylopharyngeus muscle.

Visceral motor; Presynaptic parasympathetic fibres synapse at the otic ganglion to innervate the parotid gland.

General somatic sensory; the tympanic, carotid sinus, pharyngeal, tonsillar and lingual nerves are branches.

Special sensory; taste fibres are transmitted from the posterior third of the tongue to the sensory inferior ganglion of the nerve at the anterior part of the jugular foramen, where the ganglion is located.

Clinical Relevance[edit | edit source]

The glossopharyngeal nerve palsy can have a number of effects on the body based on its distribution. Impairment of swallowing, loss of bitter and sour taste could be implicated. Patients with higher cervical-level spinal cord lesion and ventilator-dependent neuromuscular disorders who survive on glossopharyngeal breathing may have their condition complicated in an event of weakness or paralysis of the glossopharyngeal nerve.

Assessment[edit | edit source]

The gag reflex of the mouth is tested, the patient is asked to swallow or cough, and speech difficulties are evaluated as part of the clinical tests performed to detect if the glossopharyngeal nerve has been injured. To assess for taste impairment, the doctor may use bitter and sour substances to test the posterior one-third of the tongue. The patient's overall sensation and taste on the posterior part of the tongue can be tested to determine the integrity of the glossopharyngeal nerve. Because only the afferent fibres involved in the gag reflex are conveyed by the glossopharyngeal nerve, the gag reflex can also be used to evaluate the glossphyaryngeal nerve, but it also evaluates the vagus nerve.

References[edit | edit source]

  1. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Philadelphia; Lippincott Williams and Wilkins, 2017
  2. Netter FH. Atlas of Human Anatomy. Philadelphia; Elsevier, 2019