CRANIAL - III (CN IX, X, XI & XII)

DR. SANGEETA KOTRANNAVAR ASSISTANT PROFESSOR DEPT. OF ANATOMY USM KLE IMP BELAGAVI

OBJECTIVES

• Describe the functional component, nuclei of origin, course, distribution and functional significance of IX, X, XI and XII

• Describe the applied anatomy of cranial nerves IX, X, XI and XII overview Relationship of the last four cranial nerves at the base of the skull

The last four cranial nerves arise from medulla & leave the skull close together, the glossopharyngeal, vagus & accessory through , and the hypoglossal through the hypoglossal canal Functional components OF CN Afferent Efferent

General General somatic afferent fibers General somatic efferent fibers Somatic (GSA): transmit exteroceptive & (GSE): innervate skeletal muscles proprioceptive impulses from skin of somatic origin & muscles to somatic sensory nuclei

General General visceral afferent General visceral efferent(GVE): transmit visceral fibers (GVA): transmit motor impulses from general visceral interoceptive impulses motor nuclei &relayed in parasympathetic from the viscera to the ganglions. Postganglionic fibers supply visceral sensory nuclei glands, smooth muscles, vessels & viscera

Special Special somatic afferent fibers (SSA): ------Somatic transmit sensory impulses from special sense organs eye , nose & ear to brain Special Special visceral afferent fibers Special visceral efferent fibers (SVE): visceral (SVA): transmit sensory transmit motor impulses from the impulses from special sense brain to skeletal muscles derived from taste (tounge) to the brain pharyngeal arches : include muscles of mastication, face, & Cranial Nerve Nuclei in : Schematic picture Functional components OF CN GLOSSOPHARYNGEAL NERVE

• Glossopharyngeal nerve is the 9th cranial nerve.

• It is a mixed nerve, i.e., composed of both the motor and sensory fibres, but predominantly it is sensory.

• It derives its name from the fact that it provides sensory innervation to the and pharynx.

• Nerve of 3rd branchial arch NUCLEI OF GLOSSOPHARYNGEAL NERVE Functional components and nuclei of the glossopharyngeal nerve FUNCTIONAL COMPONENTS OF GLOSSOPHARYNGEAL NERVE 1. Special visceral efferent (SVE) fibres: • They arise from . • They supply the stylopharyngeus muscle (from brachial arch so special)

2. General visceral efferent (GVE) fibres: • They are preganglionic parasympathetic fibres and arise from the inferior salivatory nucleus & relay in . • They supply the secretomotor fibres to the parotid gland. 3. Special visceral afferent (SVA) fibres: • They carry taste sensations from the posterior 1/3rd of tongue including vallate papillae and terminate in the nucleus tractus solitarius.

4. General visceral afferent (GVA) fibres: • They carry general sensations of pain, touch, and temperature from the mucous membrane of the pharynx, tonsil, soft palate, and posterior 1/3rd of tongue & terminate in the dorsal nucleus of the vagus.

Course and Relations

• It arises from the upper part of lateral aspect of the medulla between the olive & inferior cerebellar peduncle by 3-4 rootlets.

• Rootlets unite to form a single trunk, runs forward & laterally to leave the cranial cavity by passing through the anterior compartment of the jugular foramen

• It passes through smaller superior ganglion lies within & larger inferior ganglion lies just below the jugular foramen & contains cell bodies of most of the sensory fibers of the nerve. • From foramen, nerve passes downward & forward between (ICA) & . • It then proceeds between internal & external carotid arteries deep to styloid process to reach the lateral aspect of the stylopharyngeus which it supplies.

OVERVIEW OF GLOSSOPHARYNGEAL NERVE Branches of CN IX

• Observe the modality of each branch & relate it to function of nerve Branches of CN IX

1. Tympanic branch (Jacobson’s nerve): forms tympanic plexus (over the promontory of the middle ear)  the lesser petrosal nerve, carries secretomotor fibers to otic ganglion supplies parotid gland via auriculotemporal N BRANCHES OF GLOSSOPHARYNGEAL NERVE IN TYMPANIC CAVITY

• It leaves the inferior ganglion and enters the middle ear through the tympanic canaliculus situated at the bony edge between the jugular foramen and carotid canal. • It forms the tympanic plexus over the promontory of the middle ear. • The tympanic plexus gives off: (a) the lesser petrosal nerve and (b) twigs to tympanic cavity, auditory tube, and mastoid air cells.

2. Carotid nerve (nerve of Herring): Sensory branch to carotid sinus and carotid body. It serves as an afferent limb for baro-receptor & chemo-receptor reflexes from the carotid sinus & carotid body to regulate the heart rate and respiration, respectively.

3. Pharyngeal branch: Carries sensation from mucous membrane of pharynx. It joins the pharyngeal branches of the vagus and the cervical sympathetic chain to form the pharyngeal plexus on the middle constrictor of the pharynx. 4.Tonsillar branches: They supply the mucous membrane of tonsil and palate.

5. Lingual branches: They supply the posterior one-third of the tongue and vallate papillae and convey taste and general sensations.

6. Branch to stylopharyngeus: It is the only motor branch that supplies stylopharyngeus muscle.

Applied anatomy

1. Lesions of glossopharyngeal nerve: complete lesion of the glossopharyngeal nerve results in: (a) Loss of taste and general sensations over the posterior one-third of the tongue, (b) Loss of general sensation of pharynx, tonsils & post.1/3rd of tongue leads to difficulty in , (c) the loss of the salivation from the parotid gland, and (d) the unilateral loss of the gag reflex OF CN 9

VAGUS NERVE • Vagus nerve is the 10th cranial nerve. • It is a mixed nerve, i.e., composed of both the motor and sensory fibres but predominantly it is motor. • It is the longest and most widely distributed cranial nerve. • It is so called because of its extensive vague course and distribution. • It is a vagrant or wandering nerve. • Its field of distribution extends beyond the head and to the and . • It conveys most of the efferent fibres of the cranial part of the parasympathetic outflow and distributes the fibres of an cranial part of the .

NUCLEI OF VAGUS NERVE Nuclei and Functional components of vagus nerve

Efferents

Afferents

Functional components and nuclei of the vagus nerve 1. Special visceral efferent fibres: supply the muscles of palate, pharynx, and larynx (brachial muscles). They arise from nucleus ambiguus.

2. General visceral efferent fibres: arise from the dorsal nucleus of vagus, and provide parasympathetic innervation to heart, bronchial tree, and most of the GIT. 3. Special visceral afferent fibres: carry taste sensations from the posteriormost part of the tongue and and terminate in the nucleus tractus solitarius.

4. General visceral afferent fibres: carry general sensations from the mucous membrane of pharynx, larynx, trachea, esophagus, and thoracic and abdominal viscera and terminate in the nucleus tractus solitarius and some in the dorsal nucleus of the vagus.

5. General somatic afferent fibres: carry general sensations from skin of the auricle and terminate in the nucleus of the spinal tract of the .

Course and Relations of vagus

• vagus nerve arises from the lateral aspect of the medulla between olive & inferior cerebellar peduncle by about 10 rootlets below & in line of rootlets of the CN 9. • These nerve rootlets unite to form the nerve trunk which runs laterally, crosses the , and leaves the cranial cavity by passing through the middle part of the jugular foramen • A smaller superior ganglion lies within & larger inferior (nodose) ganglion lies just below the jugular foramen. • Cranial root of CN 11 joins below inf. Jugular vein. • Runs vertically downward within the in the neck first between the internal jugular vein and internal carotid artery

• At the root of the neck, the Right nerve enters the thorax.

• Right vagus nerve enters the thorax by crossing in front & winds round the right subclavian artery

• Left vagus nerve enters the thorax by passing between the left common carotid & left subclavian arteries, then winds around the arch of aorta.

VISCERAL AND SENSORY DISTRIBUTION OF VAGUS NERVE BRANCHES OF VAGUS NERVE Branches and Distribution 1. Meningeal branch: • Arises from superior ganglion • It supply - dura mater of .

2. Auricular branch (Arnold’s nerve or Alderman’s nerve): • Arises from the superior ganglion • It supplies - floor of the meatus and the tympanic membrane. • Stimulation of this nerve, as in syringing of the ear, may cause reflex coughing (ear cough), vomiting, and even cardiac arrest. 3. Pharyngeal branch: • Takes part in the formation of pharyngeal plexus. • supplies: all the muscles of pharynx except the stylopharyngeus, (which is supplied by CN 9) • supplies: all the muscles of soft palate except the tensor palati (which is supplied by CN V3 through the nerve to medial pterygoid).

4. Branches to carotid body: • Arises from the inferior ganglion & innervates carotid body & sinus.

5. (nerve of 4th arch): • External laryngeal nerve – supplies • Internal laryngeal nerve (sensory) passes thro’ thyrohyoid membrane & sensory to mucous membrane above vocal cord

7. Recurrent laryngeal nerve (nerve of 6th arch) • Supplies – all intrinsic muscle of larynx except cricothyroid • Sensory below the vocal folds

8.Cardiac branches 9.Pulmonary branches 10. Esophageal branches

In abdomen 11.Gastric branches 12.Hepatic branches 13. Coeliac branches

• Forms plexuses near organs and postganglionic parasympathetic fibers supplies heart, lungs, GIT upto right 2/3rd of transverse colon. Vagus is secretomotor to glands, increase peristalsis & inhibitory to sphincter (for GIT). APPLIED ANATOMY

• Lesions of vagus nerve: The bilateral lesions of vagus nerve cause: – hoarseness of voice- due to unilateral paralysis of laryngeal muscles – flattering of palatal arches –due to paralysis of palate muscles – Loss of gag reflex of efferent limb – Dysphagia & loss of cough reflex – due to anesthesia of pharynx & larynx Clinical testing of vagus nerve: ACCESSORY NERVE • Accessory nerve is the 11th cranial nerve.

• It is purely motor.

• It consists of two roots: cranial and spinal.

• The cranial root is accessory to the vagus and its fibres are distributed through the vagus nerve.

• The spinal root has an independent course and is generally regarded as spinal accessory nerve, or simply as accessory nerve. NUCLEUS AND COURSE OF ACCESSORY NERVE Functional components and nuclei of the accessory nerve Functional components and nuclei of the accessory nerve 1. Special visceral efferent fibres: provide motor supply to the muscles of soft palate, pharynx, and larynx. They arise from the nucleus ambiguus and form the cranial root.

2. General somatic efferent fibres: provide motor supply to the sternocleidomastoid and muscles. They arise from the spinal nucleus of accessory nerve, in the ventral horns of the upper five spinal segments. Course and Relations of CN XI

• The cranial root arises by 4-6 rootlets from the posterolateral sulcus of the medulla between the olive and inferior cerebellar peduncle.

• These rootlets unite together to form a single trunk which runs laterally along with the 9th and 10th cranial nerves to reach the jugular foramen where it is joined by the spinal root.

• spinal root arises by a number of rootlets from ventral horn of the (C1-5).

• These rootlets unite to form a single trunk which ascends in the vertebral canal to enter the cranial cavity through the behind the vertebral artery.

• The spinal root leaves the skull through the jugular foramen where it fuses with the cranial root. Distribution of CN IX Cranial root of the accessory nerve via the vagus nerve and pharyngeal plexus of nerves supplies:

1. All the muscles of the palate except the tensor palati which is supplied by the medial pterygoid nerve br. of CNV3. 2. All the muscles of the pharynx except the stylopharyngeus which is supplied by CN IX. 3. All the muscles of larynx. The spinal root of the accessory nerve supplies the following two muscles:

1. Sternocleidomastoid muscle along with C2 and C3 spinal nerves. 2. Trapezius muscle along with C3 and C4 spinal nerves. APPLIED ANATOMY Lesions of spinal accessory nerve: It may be damaged – by the fracture base of the skull through the jugular foramen – or stab wounds in the neck – or during the surgical removal of .

Unilateral/lesion of the spinal accessory nerve proximal to sternocleidomastoid causes: • – ipsilateral paralysis of the sternocleidomastoid, with the result that the patient is unable to tilt his head toward the ipsilateral shoulder and unable to turn his face toward the opposite side, • – paralysis of trapezius, with the result that the patient is unable to shrug his shoulder against the resistance. Of CN XI • is the 12th cranial nerve. • It is purely a motor nerve. NUCLEI OF HYPOGLOSSAL NERVE Functional components and nucleus of the origin of the hypoglossal nerve

• General somatic efferent fibres: These fibres arise from the and supply all the muscles of the tongue (extrinsic and intrinsic) which develop from occipital myotomes. Course and Relations of CN XII • The hypoglossal nerve arises on the ventral aspect of the medulla from the anterolateral sulcus between the pyramid and the olive by 10–15 rootlets.

• The rootlets fuse to form two roots, enter hypoglossal canal

• In the canal, the two roots unite to form a single trunk and come out of the cranial cavity.

• After coming out of the cranial cavity, the nerve lies deep, to the internal carotid hyoglossus artery and 9th &10th CNs.

• It then passes forward between the internal jugular vein and the internal carotid artery. • Runs superficially to carotid arteries & loop of lingual artery, runs on hyoglossus then supplies tongue muscles Branches and Distribution of CNXII

Hyoglossus

1. Branches of the hypoglossal proper: They supply all the muscles of the tongue except palatoglossus which is supplied by the cranial root of accessory via the pharyngeal plexus. 2. Branches of the hypoglossal nerve containing C1 fibres:

These are as follows: (a) Meningeal branch (b) Descendens hypoglossi or upper root of ansa cervicalis (c) Nerve to thyrohyoid (d) Nerve to geniohyoid

APPLIED ANATOMY

Lesions of hypoglossal nerve: Lower motor (LMN) type of paralysis of muscles of the tongue on same side. On asking the patient to protrude his tongue, the tip of the tongue deviates to the paralyzed side due to the unopposed action of the muscles of healthy side.

Upper (UMN) type of paralysis; nucleus receives corticonuclear fibres only from contralateral hemisphere, UMN lesions causes paralysis of opposite half of tongue, & on protrusion deviates to opposite side of lesion. There will also be fasciculations in tongue on the affected side & mucous membrane will show wrinkling due to wasting of muscles.

SUMMARY Cranial Nerve Nuclei in Brainstem:

Summary OSPE

Identify structures

E

A

F B c D

CN IX CN X CN XI CN XI CN XII ??