Lesions affecting the glossopharyngeal nerve also usually involve the vagus and therefore syndromes affecting both nerves are much more common than nerve lesions occurring in relative isolation. Localization of Lesions Affecting the Glossopharyngeal Nerve ![]() Salivary secretion (from the parotid gland) may be decreased, absent, or occasionally increased with glossopharyngeal lesions, but these changes are difficult to demonstrate without specialized quantitative studies. Medical neurosciences: an approach to anatomy, pathology, and physiology by system and levels, 2nd ed. Dorsal roots of C1 through C6 in the upper cervical spinal cord are also shown. Ventral view of medulla and cranial nerves IX, X, and XI exiting together through the jugular foramen. Unilateral absence of these reflexes is seen with glossopharyngeal nerve lesions.įIG. The afferent arcs of these reflexes probably involve the glossopharyngeal nerve, whereas the efferent arcs involve both the glossopharyngeal and vagus nerves. ![]() The palatal reflex consists of elevation of the soft palate and ipsilateral deviation of the uvula with stimulation of the soft palate. The response is tongue retraction associated with elevation and constriction of the pharyngeal musculature. The pharyngeal or gag reflex is tested by stimulating the posterior pharyngeal wall, tonsillar area, or base of the tongue. These areas may be ipsilaterally anesthetic with glossopharyngeal lesions. ![]() Sensation (pain, soft touch) is tested on the soft palate, posterior third of the tongue, tonsillary regions, and pharyngeal wall. The integrity of taste sensation may be tested over the posterior third of the tongue and is lost ipsilaterally with nerve lesions. (However, the palate elevates symmetrically with vocalization.) Motor paresis may be negligible with glossopharyngeal nerve lesions, although mild dysphagia may occur and the palatal arch may be somewhat lower at rest on the side of glossopharyngeal injury. Stylopharyngeal function is difficult to assess. The postganglionic fibers then travel by way of the auriculotemporal branch of the trigeminal nerve, carrying secretory and vasodilatory fibers to the parotid gland. These parasympathetic preganglionic fibers leave the glossopharyngeal nerve at the petrous ganglion and travel by way of the tympanic nerve or Jacobson’s nerve (coursing in the petrous bone) and the lesser superficial petrosal nerve to reach the otic ganglion (just below the foramen ovale), where they synapse. The parasympathetic fibers carried in the glossopharyngeal nerve originate in the inferior salivatory nucleus, located in the periventricular gray matter of the rostral medulla, at the superior pole of the rostral nucleus of cranial nerve X. The glossopharyngeal nerve also carries chemoreceptive and baroreceptive afferents from the carotid body (chemoreceptors) and carotid sinus (baroreceptors), respectively, by way of the carotid sinus nerve ( nerve of Hering). Taste afferents and general visceral afferent fibers have their cell bodies in the petrous ganglion and terminate mainly in the nucleus of the solitary tract (the rostral terminating fibers convey taste, and the caudal terminating fibers convey general visceral sensation) exteroceptive afferents have their cell bodies in the superior and petrous ganglia and terminate in the spinal nucleus of the trigeminal nerve. By way of the tympanic branch of the glossopharyngeal nerve ( Jacobson’s nerve), sensation is supplied to the tympanic membrane, eustachian tube, and the mastoid region. The sensory fibers carried in the glossopharyngeal nerve include taste afferents, supplying the posterior third of the tongue and the pharynx, and general visceral afferents from the posterior third of the tongue, tonsillary region, posterior palatal arch, soft palate, nasopharynx, and tragus of the ear. The motor fibers originate from the rostral nucleus ambiguus and innervate the stylopharyngeus muscle (a pharyngeal elevator) and (with the vagus nerve) the constrictor muscles of the pharynx. The nerve winds around the lower border of the stylopharyngeus muscle (which it supplies) and then penetrates the pharyngeal constrictor muscles to reach the base of the tongue. Within or distal to this foramen, the glossopharyngeal nerve widens at the superior and the petrous ganglia and then descends on the lateral side of the pharynx, passing between the internal carotid artery and the internal jugular vein. These three nerves then travel together through the jugular foramen. ![]() The nerve emerges from the posterior lateral sulcus of the medulla oblongata dorsal to the inferior olive in close relation with cranial nerve X (the vagus nerve) and the bulbar fibers of cranial nerve XI (the spinal accessory nerve) ( Fig. The glossopharyngeal nerve contains motor, sensory, and parasympathetic fibers. Cranial Nerves IX and X (The Glossopharyngeal and Vagus Nerves)Īnatomy of Cranial Nerve IX (Glossopharyngeal Nerve)
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |