Glossopharyngeal Nerve
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Description
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
The glossopharyngeal nerve appears from the lateral part of the medulla oblongata following anterolaterally to exit the brainbox through the ventral aspect of the jugular foramen, where the sensory superior and the nerve inferior ganglia are located. The nerve follows and supplies the stylopharyngeus muscle, runs between the superior and middle pharyngeal constrictor muscles to reach the oropharynx and tongue, and contributes sensory innervation to the pharyngeal plexus of nerves. [2]
Function
The glossopharyngeal nerve has somatic motor, visceral motor, general somatic sensory, and special sensory (taste) functions.
- Somatic Motor: Efferent fibres innervate the stylopharyngeus muscle (elevates the pharynx and larynx).
- 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.
The video below is a 5 minutes simple explanation of the glossopharyngeal nerve
Clinical Relevance
The glossopharyngeal nerve palsy can have several effects on the body based on its distribution. Impairment of swallowing and loss of bitter and sour taste could be implicated. Patients with higher cervical-level spinal cord lesions 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[4].
Glossopharyngeal neuralgia[5] this rare condition may happen because of injury, tumors, infections, surgeries, malformation structures in the throat or neck, or even compression by a vessel or dysfunction of the central pons. This condition is associated with sudden, sharp pain on one side of the throat, tonsils, base of the tongue, or just below the jaw, pain may come in short episodes lasting from a few seconds to a few minutes[6].
Assessment
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 glossopharyngeal nerve and the vagus nerve.
References
- ↑ Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Philadelphia; Lippincott Williams and Wilkins, 2017
- ↑ Netter FH. Atlas of Human Anatomy. Philadelphia; Elsevier, 2019
- ↑ Complete Anatomy. Anatomy Dissected: Cranial Nerve IX (glossopharyngeal nerve) . Available from: http://www.youtube.com/watch?v=RnJBYNTsOto [last accessed 30/12/2024]
- ↑ Nygren-Bonnier M, Wahman K, Lindholm P, Markström A, Westgren N, Klefbeck B. Glossopharyngeal pistoning for lung insufflation in patients with cervical spinal cord injury. Spinal cord. 2009 May;47(5):418-22.
- ↑ Savarimuthu MK, Nair AK. A case of isolated unilateral glossopharyngeal nerve palsy. Clinical Medicine & Research. 2020 Apr 13;18(1):37-41.
- ↑ Khan M, Nishi SE, Hassan SN, Islam MA, Gan SH. Trigeminal neuralgia, glossopharyngeal neuralgia, and myofascial pain dysfunction syndrome: an update. Pain Research and Management. 2017;2017(1):7438326.
- ↑ onlinemedicalvideo. Neurologic Exam Cranial Nerves Normal : Cranial Nerves 9 & 10- Sensory and Motor: Gag Reflex. Available from: http://www.youtube.com/watch?v=uq8cRzi1nkU[last accessed 1/8/2025]