GLOSSOPHARYNGEAL (CN IX) AND VAGUS (CN X) NERVES

DR. SUMIT KAMBLEDM RESIDENTDEPT. OF NEUROLOGYGMC, KOTA

GLOSSOPHARYNGEAL NERVE• Distributed principally to tongue and pharynx.

• Conveys general sensory as well as special sensory (taste) fibers from posterior third of the tongue.

• Provides general sensory innervation to pharynx, area of the tonsil, internal surface of the tympanic membrane, and skin of the external ear.

• Conveys GVAs from the carotid body and carotid sinus.

• Its skeletomotor neurons innervate the stylopharyngeus muscle, and its parasympathetic component innervates the parotid gland.

ANATOMY AND PHYSIOLOGY

• Both motor and sensory

• Motor - Stylopharyngeus

• Parasympathetic secretomotor - Parotid gland

• Sensory: tympanic cavity, Eustachian tube, fauces, tonsils, nasopharynx, uvula, inferior surface of the soft palate and posterior (postsulcal) third of the tongue.

COURSE

MOTOR FUNCTION• Motor Nucleus - rostral part of the nucleus ambiguus, it is

situated deep in the reticular formation medial to the spinal tract and nucleus of trigeminal nerve.

• Supplies- stylopharyngeus.

SENSORY FUNCTION

• Sensory neurons - located in superior and inferior glossopharyngeal ganglia.

• GVA - convey information from carotid body and carotid sinus, as well as visceral sensation from the pharynx;

• SVA - convey taste sensation. • GSA – convey exteroceptive sensation from the mucous

membranes of the tympanic cavity, mastoid air cells, and auditory canal via the tympanic plexus and tympanic branch.

PARASYMPATHETIC FUNCTION• Supplies parasympathetic innervation to parotid gland and to

mucous membranes of posterior inferior mouth and pharynx.

• Parasympathetic nuclei in lower brainstem are the superior and inferior salivatory and the dorsal motor nucleus of CN X (DMNX).

BRANCHES

1. Tympanic.2. Stylopharyngeus.3. Pharyngeal.4. Tonsillar.5. Lingual .

CLINICAL EVALUATIONMOTOR FUNCTION• Motor paresis may be negligible • Stylopharyngeal function difficult to assess.• Mild dysphagia, lower palatal arch on same side.

SENSORY FUNCTION• Loss of taste sensation over post. third of tongue on same side.• Pain and touch over soft palate, post. third of the tongue,

tonsilar regions and pharyngeal wall over ipsilateral side.

REFLEX FUNCTION• Pharyngeal or Gag reflex• Palatal reflex

• Afferent – Glasopharyngeal• Efferent- Glasopharyngeal and Vagus

AUTONOMIC FUNCTION• Salivary secretion from parotid may be decreased.

LOCALIZATION OF LESSIONSSUPRANUCLER• Unilateral – No deficit• Bilateral- Pseudobulbar palsy• Severe dysphagia, pseudo-bulbar signs ( pathological laughter

and crying, spastic tongue, spastic dysarthria) , exaggerated gag reflex.

NUCLEAR AND INTRAMEDULLARY• Include Syringobulbia, demyelinating disease, vascular disease,

MND and Malignancy.• Commonly involve other cranial nerve and other brainstem

structure.

EXTRAMEDULLARY LESSIONS1. Cerebellopontine angle syndrome –• CP angle tumors especially acoustic tumors • Associated with tinnitus, deafness and vertigo (CN VIII), facial

sensory abnormalities (cranial verve V) and cerebellar signs.

2. Jugular foramen syndrome (Vernet syndrome)• Injure CN IX, X and XI, which travel through this foramen.• Glomus jugulare tumors, neuroma, metastasis, cholesteatoma,

meningioma, infections and giant cell arteritis.

3. Lesions within Retropharyngeal and Retroparotid space• May be injured by neoplasm ( nasopharyngeal carcinoma),

abscesses, adenopathy, aneurysm, trauma or surgical procedures (carotid endarterectomy).

• Collet-Sicard syndrome ( CN IX, X, XI and XII)• Villaret syndrome (CN IX, X, XI and XII, sympathetic chain

and occasionally CN VII).

GLASSOPHARYNGEAL NEURALGIA• Attacks of severe lancinating pain originating in one side of the

throat or tonsillar region and radiating along the course of the eustachian tube to the tympanic membrane, external auditory canal, behind the angle of the jaw, and adjacent portion of the ear.

• Trigger zones• Pain lasting for seconds to minutes may be brought on by

talking, eating, swallowing, or coughing. • It can lead to syncope, convulsions, and rarely to cardiac arrest

because of stimulation of the carotid sinus reflex.

CAROTID HYPERSENSITIVITY• Inadvertent activation of the baroreceptors in the carotid sinus

causing bradycardia and hypotension.

• Identifiable etiologies may include constriction around the neck (e.g., tight collar) or a mass in the neck impinging on the sinus, but many cases are idiopathic.

VAGUS NERVE• Longest and most widely distributed CN

• Vagus nerve is associated with the derivatives of the fourth pharyngeal arch.

• Connects with four brainstem nuclei: nucleus ambiguus, DMNX, nucleus of the spinal tract of CN V, and nucleus of the solitary tract.

• Sensory: GSA sensation from pharynx, larynx, ear, and meninges and GVA from the larynx, viscera of the thorax and abdomen, and receptors in the aorta.

• Special Sensory: Provides taste sensation to the epiglottis and root of the tongue.

• Motor: Provides motor innervation to the majority of the muscles of the pharynx, soft palate and larynx.

• Parasympathetic: Innervates the smooth muscle of the trachea, bronchi and gastro-intestinal tract and regulates heart rhythm.

ANATOMYHead• Originates from the medulla and exits the cranium via jugular

foramen, with the glossopharyngeal and accessory nerves .

• Within the cranium, auricular branch arises. This supplies sensation to the posterior part of the external auditory and canal external ear.

In the Neck• Passes into the carotid sheath, travelling inferiorly with the

internal jugular vein and common carotid artery. • At the base of neck, right and left nerves have differing

pathways

• Right vagus nerve passes anterior to the subclavian artery and posterior to the sternoclavicular joint, entering the thorax.

• Left vagus nerve passes inferiorly between the left common carotid and left subclavian arteries, posterior to the sternoclavicular joint, entering the thorax.

Several branches arise in the neck:• Pharyngeal branches – motor innervation to majority of the

muscles of the pharynx and soft palate.

• Superior laryngeal nerve – Splits into internal and external branches.

• Recurrent laryngeal nerve - It innervates the majority of the intrinsic muscles of the larynx.

In the Thorax• Right vagus nerve forms posterior vagal trunk, and the left

forms anterior vagal trunk. 

• Two other branches arise in the thorax:• Left recurrent laryngeal nerve – innervate majority of the

intrinsic muscles of the larynx.• Cardiac branches – regulate heart rate and provide visceral

sensation to the organ.

• Vagal trunks enter the abdomen via the oesophageal hiatus, an opening in the diaphragm.

• In the Abdomen• In the abdomen, the vagal trunks terminate by dividing into

branches that supply the oesophagus, stomach and the small and large bowel (up to the splenic flexure).

Vagus has two sensory ganglia. 1. Superior (jugular) vagal ganglion located in the jugular fossa

of the temporal bone;2. Inferior (nodose) ganglion is located just distal to the jugular

foramen.

10 major terminal branches that arise at different levels: • (a) meningeal, (b) auricular, (c) pharyngeal, (d) carotid, (e)

superior laryngeal, (f ) recurrent laryngeal, (g) cardiac, (h) esophageal, (i) pulmonary, and (j) gastrointestinal.

SENSORY FUNCTION• There are somatic and visceral components to the sensory

function of the vagus nerve.

• Superior ganglion primarily conveys somatic sensation,• Inferior ganglion relays general visceral sensation and taste.

• Somatic sensory portion conveys pain, temperature, and touch sensation from the pharynx, larynx, ear canal, external surface of the tympanic membrane, and meninges of posterior fossa.

• General sensory fibers from the region of the ear, ear canal, and tympanic membrane travel in the auricular branch (nerve of Arnold).

• GSA fibers in CN X synapse in the nucleus of the spinal tract of CN V

• In the larynx, GSA fibers from above the vocal folds travel in the internal laryngeal branch of the superior laryngeal nerve;

• Fibers from below the vocal folds travel with the recurrent laryngeal nerve.

• Viscera sensation (GVA) is that from the organs of the body. • Central processes terminate in the caudal portion of the solitary

tract.

• The vagus nerve innervates:• Laryngopharynx – via the internal laryngeal nerve.• Superior aspect of larynx (above vocal folds) – via the internal

laryngeal nerve.• Heart – via cardiac branches of the vagus nerve.• Gastro-intestinal tract (up to the splenic flexure) – via the

terminal branches of the vagus nerve.

• Collaterals to reticular formation, DMNX, and other CN nuclei mediate important visceral reflexes and are involved in the regulation of cardiovascular, respiratory, and gastrointestinal function.

• Special visceral afferent (SVA )- Vagus nerve has a minor role in taste sensation.

• It carries afferent fibres from the root of tongue and epiglottis.

MOTOR FUNCTION• Vagus nerve innervates the majority of the muscles associated

with the pharynx and larynx. • These muscles are responsible for the initiation of swallowing

and phonation.

Muscles of the Pharynx• Most of the muscles of the pharynx are innervated by

 pharyngeal branches of the vagus nerve:1. Superior, middle and inferior pharyngeal constrictor muscles2. Palatopharyngeus3. Salpingopharyngeus

• Muscles of the Larynx• Innervation to the intrinsic muscles of the larynx is achieved via

 recurrent laryngeal nerve and external branch of the superior laryngeal nerve.

Recurrent laryngeal nerve:• Thyro-arytenoid• Posterior crico-arytenoid• Lateral crico-arytenoid• Transverse and oblique arytenoids• VocalisExternal laryngeal nerve:• Cricothyroid

Other Muscles• In addition to the pharynx and larynx, the vagus nerve also

innervates palatoglossus of the tongue, and the majority of the muscles of the soft palate.

PARASYMPATHETIC FUNCTION• Vagus nerve is main parasympathetic outflow to the heart and

gastro-intestinal organs.

• Parasympathetic component of CN X arises from the DMNX.

• Vagal discharge causes bradycardia, hypotension, bronchoconstriction, bronchorrhea, increased peristalsis, increased gastric secretion, and inhibition of adrenal function.

The Heart• Cardiac branches arise in the thorax, conveying

parasympathetic innervation to the sino-atrial and atrio-ventricular nodes of the heart

• Stimulate reduction in the resting heart rate. They are constantly active, producing a rhythm of 60 – 80 beats per minute

Gastro-Intestinal System• Sends branches to the oesophagus, stomach and most of the

intestinal tract – up to the splenic flexure of the large colon.

• Stimulate smooth muscle contraction and glandular secretions in these organs.

CLINICAL EXAMINATION MOTOR FUNCTION1. Character of voice and ability to swallow- • With acute unilateral lesions, speech may have a nasal quality

and dysphagia more marked for liquids than solids, with a tendency to nasal regurgitation.

2. Examination of the soft palate• Position of palate and uvula• With a unilateral lesion -

weakness of the levator veli palatini and musculus uvulae, causes a droop of the palate and flattening of the palatal arch

• Preserved function of the tensor veli palatini may prevent marked drooping of the palate.

• On phonation, median raphe deviates toward the normal side.

3. Palatal gag reflex - may be lost on involved side because of interruption of motor rather than sensory path.

4. Bilateral vagus involvement• Palate cannot elevate on phonation; it may or may not droop,

depending on the function of the tensor veli palatini.• Palatal gag reflex is absent bilaterally. • Nasal speech and nasal regurgitation of liquids.

5. Vocal cord weakness - alters the character and quality of the voice and may produce abnormalities of articulation, difficulty with respiration, and impairment of coughing.

• Most common cause of vocal cord paralysis is a lesion of one recurrent laryngeal nerve.

SENSORY FUNCTION• Not clinically important and cannot be adequately tested.

REFLEX• Unilateral vagal lesion depress the ipsilateral gag reflex by

interrupting the efferent arc.

LOCALIZATION OF LESIONSSUPRANUCLEAR LESIONS• Unilateral – No deficit• Bilateral- Pseudobulbar palsy

NUCLEAR LESIONS AND BRAINSTEM LESIONS• Nuclear- result in ipsilateral palatal, pharyngeal and laryngeal

paralysis and usually associated with affection of other CN nuclei, roots and long tracts.

• Causes- Vascular, tumors, syringobulbia, MND and inflammatory disease.

LESIONS WITHIN POSTERIOR FOSSA• Lesion at this location usually also involve the CN IX, XI and

XII.• Causes include primary (Glomus jugulare) and metastatic

tumors, infections, carcinomatous meningitis, sarcoidosis, GBS and trauma.

SYNDROME CN involved

Jugular foramen syndrome of Vernet IX, X, XI

Schmidts syndrome X, XI

Hughlings Jackson syndrome X, XI, XII

Collet-Sicard syndrome IX,X, XI, XII

LESION AFFECTING VAGUS NERVE PROPER• Trunk of vagus nerve may be injure in neck and thorax by

tumors, aneurysms of internal carotid artery, trauma and enlarged lymph nodes.

• Result in complete ipsilateral vocal cord paralysis associated with unilateral laryngeal anesthesia.

LESIONS OF SUPERIOR LARYNGEAL NERVE• Damaged by trauma, surgery or tumor.• Few clinical findings.• Mild hoarseness due to paralysis of cricothyroid.

LESIONS OF RECURRENT LARYNGEAL NERVE

• May be damaged by tumors in neck, especially carcinoma of the thyroid, cervical adenopathy, metastatic lesions, Hodgkin disease, lymphosarcoma, aortic aneurysms, mitral stenosis with enlargement of the left atrium, pericarditis, mediastinal and apical tumors, stab wounds in the neck, or accidental trauma during a thyroidectomy or other surgical procedure.

UNILATERAL- flaccid dysphonia with breathiness and mild inspiratory stridor; Diplophonia may occur.• On laryngoscopy paralyzed vocal cord lies near midline.

BILATERAL -cause abduction impairment and leave the vocal cords approximating each other in the midline. • Results in dyspnea and inspiratory stridor.• Can be seen after thyroidectomy, polyneuropathy or carcinoma

of thyroid or esophagus.

THANK YOU

REFERENCES• Localization in clinical neurology, Paul Braziz, 6th edition• DeJongs the Neurological examination 7th edition