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College of Medicine – كلية الطب Cranial Nerves Dr.Munirha Batarfi MD, MSc & PhD College of Medicine – كلية الطب Cranial Nerves - Olfactory (I) - Optic (II) - Oculomotor (III) - Trochlear (IV) - Trigeminal (V) - Abducens (VI) - Facial (VII) - Vestibulocochlear (VIII) - Glossopharyngeal (IX) - Vagus (X) - Accessory (XI) - spinal accessory(XII) - Hypoglossal (XII) 2 Cranial Nerves College of Medicine – كلية الطب There are 12, paired cranial nerves. The first 2 cranial Ns. attach directly to forebrain (frontal lobe) , while the rest attach to brain stem. 1- Olfactory system is attached to forebrain 2- Optic N. also is discribed in visual pathway. Cranial Ns. from 3 - 12 have nuclei (cranial N.nucluei) in the brain stem , receiving afferents Fs. Or send efferent Fs. as the cranial Ns. College of Medicine – كلية الطب Cranial Nerves College of Medicine – كلية الطب 3 & 4- Occulomotor & trochlear Ns. are attached to midbrain. 5- Trigeminal N. is attached to antero-lateral surface of pons. 6 , 7 & 8- Abducent, Facial & vestibulo-cochlear Ns. are lying between pons & medulla oblongata from medial to lateral. 9- Hypoglossal N. is attached to antero-lateral sulcus of medulla oblongata. 10, 11, & 12- Glossopharyngeal, vagus & accessory Ns. are attached to postero-lateral sulcus of medulla oblongata College of Medicine – كلية الطب Cranial Nerves College of Medicine – كلية الطب College of Medicine – كلية الطب Abducens (VI) General characteristics of CN VI ● a pure GSE nerve that innervates the lateral rectus, which abducts the eye. ● arises from the abducent nucleus of the caudal pons. ● exits the brainstem from the inferior pontine sulcus. ● passes through the cavernous sinus to enter the orbit via the superior orbital fissure. College of Medicine – كلية الطب Abducens (VI) B. Clinical correlations: CN VI paralysis ● results in the following conditions: 1. Convergent strabismus (esotropia), with inability to abduct the eye because of the unopposed action of the medial rectus. 2. Horizontal diplopia, with maximum separation of the double images when looking toward the paretic lateral rectus. College of Medicine – كلية الطب ABDUCENT NERVE 7th n. P petrous temporal bone Pons V abducent n. 1 P College of Medicine – كلية الطب College of Medicine – كلية الطب Facial (VII) General characteristics of CN VII ● mediates facial movements, taste, salivation, and lacrimation. ● the nerve of the second pharyngeal arch. ● includes the facial nerve proper (motor division), which contains the SVE fibers that innervate the muscles of facial expression. College of Medicine – كلية الطب ● includes the intermediate nerve (sensory division), All first-order sensory neurons are found in the geniculate ganglion within the temporal bone. ● enters the internal auditory meatus and the facial canal. ● exits the facial canal and skull via the stylomastoid foramen. 13 College of Medicine – كلية الطب Facial (VII) 1. ● has cell bodies in the geniculate ganglion. ● innervates the posterior surface of the external ear via the posterior auricular branch of the facial nerve. ● projects centrally to the spinal trigeminal tract and nucleus. 2. ● has cell bodies in the geniculate ganglion. ● projects centrally to the solitary tract and nucleus. ● innervates the taste buds from the anterior two-thirds of the tongue via: College of Medicine – كلية الطب 3. Chorda tympani ● located in the tympanic cavity medial to the tympanic membrane and lateral to the malleus. ● contains SVA and general visceral afferent (GVA) fibers. ● joins the lingual nerve (a branch of CN V) 4. ● a parasympathetic component that innervates the lacrimal, submandibular, and sublingual glands. ● contains preganglionic neurons in the superior salivatory nucleus of the caudal pons. 15 College of Medicine – كلية الطب Facial (VII) Lacrimal pathway ● begins in the superior salivatory nucleus, which projects via the intermediate nerve, the greater petrosal nerve, and the nerve of the pterygoid canal to the pterygopalatine ganglion. ● continues as the postganglionic neurons of the pterygopalatine ganglion project through the inferior orbital fissure and via the zygomatic nerve (a branch of CN V) and the lacrimal nerve (a branch of CN V) to innervate the lacrimal gland. . College of Medicine – كلية الطب Submandibular pathway ● begins in the superior salivatory nucleus, which projects via the intermediate nerve and chorda tympani to the submandibular ganglion. 5. ● arises from the facial motor nucleus of the caudal pons and exits the brainstem in the CP angle. ● enters the internal auditory meatus, traverses the facial canal, sends a branch to the stapedius, and exits the skull via the stylomastoid foramen. ● innervates the muscles of facial expression, the stylohyoid, the posterior belly of the digastric, and stapedius 17 College of Medicine – كلية الطب College of Medicine – كلية الطب Facial (VII) Clinical correlations: lesions of CN VII ● result in the following conditions: 1. Flaccid paralysis of the muscles of facial expression (upper and lower face) 2. Loss of the corneal (blink) reflex (efferent limb), which may lead to corneal ulceration (keratitis paralytica) 3. Loss of taste (ageusia) from the anterior two-thirds of the tongue 4. Hyperacusis (increased acuity to sounds), due to stapedius paralysis College of Medicine – كلية الطب Facial (VII) 5. Bell’s palsy ● caused by trauma to the nerve within the facial canal. ● a lower motor neuron (LMN) lesion with paralysis of all muscles of facial expression. Bell phenomenon ● normally seen in about 75% of population. occurs when trying to close the eyes—the affected eye looks up and out. ● observable because of failure of orbicularis oculi to close eyelids. College of Medicine – كلية الطب College of Medicine – كلية الطب College of Medicine – كلية الطب College of Medicine – كلية الطب VII : Facial Nerve This nerve carries 3-types of fibres : 1- Efferent motor (branchiomotor) Fs. From facial motor nucleus in pons to : Ms. of 2nd arch , Ms.of facial expression & stapedius. 2-Afferent Taste sensory Fs. From anterior 2/3 of tounge. These Fs. are processes of cells in sensory geniculate ganglion in middle ear , and run in nervus intermedius and end in nucleus solitarius, lying in M.O. 3-Efferent preganglionic parasympathetic secretomotor Fs. Carried by sensory root of facial nerve (nervus intermedius) From sup.salivary nucleus in pons : to pterygopalatine & submandibular ganglia to lacrimal gland , palate, nasal & oral m.m, /and submandibular & sublingual salivary glands. College of Medicine – كلية الطب VII : Facial Nerve : The lateral root contains sensory & parasymp.Fs. is called nervus intermedius , but the medial root is the motor root. The sensory Fs. ends in nucleus solitarius in medulla and then Fs. project to V.P.nucleus of thalamus, which sends Fs. to sensory cortex of parietal lobe. College of Medicine – كلية الطب VII : Facial Nerve : Motor Fs. of facial nucleus in pons , looping over abducens nucleus , then leaving the brain stem to supply : Ms.of facial expression ,platysma ,stylohyoid , post.belly of digastric & stapedius of middle ear. Facial motor nucleus receives other afferents from area of brain stem for mediation of certain reflexes and also from cerebral cortex , (cortico-bulbar pyramidal tract). College of Medicine – كلية الطب VII : Facial Nerve : Reflex connections mediate 1- protective eye closure in response to sudden strong visual stimuli through Fs. from sup. Colliculus (tectum of midbrain), via facial N. to supply orbicularis oculi to close & protect the eye. 2- corneal reflex through Fs. from trigeminal sensory nucleus, to motor nucleus of facial, then via facial N. in response to tactile stimulation of cornea. College of Medicine – كلية الطب ! Afferents from cortical motor areas (cotico-bulbar Fs.) supply Ms. of upper face (frontalis & orbicularis oculi) are distributed bilaterally , but those supplying Ms. of lower face are crossed. So, Unilateral upper motor neurone lesion (UMNL) leads to lower facial Ms. paralysis of opposite side only, but upper Ms. are intact. 28 College of Medicine – كلية الطب Bell’s Palsy :LMN facial paralysis It is due to acute unilateral inflammation of facial nerve within the skull (in facial canal). Manifested by paralysis of facial muscles of upper & lower parts of face (unilaterally) on the same side of lesion.. pain around ear , - failure to close eye, absent corneal reflex, - loss of taste sensation in anterior 2/3 of tongue, & hyperacusis =increased sound perception due to paralysis of stapedius. FACIAL NERVE 1 facial n. A geniculate g. 2 College of Medicine – كلية الطب 3 B 4 temporal C tympanic cavity 1 2 a facial n. zygomatic 3 buccal 5 mandibular D E F 6 cervical Intra cranial origin -motor nucleus in the pons (1) -Superior salivary nucleus (2) -Nucleus solitarius (3) College of Medicine – كلية الطب Glossopharyngeal (IX) General characteristics of CN IX ● mediates taste (gustation), salivation, and (with CN X and CN XII) swallowing mediates input from the carotid sinus, which contains baroreceptors that monitor arterial blood pressure. ● mediates input from the carotid body, which contains chemoreceptors that monitor the carbon dioxide and oxygen concentration of the blood. College of Medicine – كلية الطب Glossopharyngeal (IX) General characteristics of CN IX ● the nerve of the third pharyngeal arch. ● predominantly a sensory nerve. ● exits the brainstem (medulla) from the postolivary sulcus with CN X. ● exits the skull via the jugular foramen with CN X and CN XI. College of Medicine – كلية الطب Glossopharyngeal (IX) 1. ● innervates the middle ear cavity and part of the external auditory meatus. ● has cell bodies in the superior glossopharyngeal ganglion. ● projects its central processes to the spinal trigeminal tract and nuc College of Medicine – كلية الطب Glossopharyngeal (IX) 2. ● innervates structures derived from endoderm (e.g., foregut). ● innervates the mucous membranes of the posterior third of the tongue, tonsil, upper pharynx (soft palate), tympanic cavity, and auditory tube. ● innervates the carotid sinus (baroreceptors) and the carotid body (chemoreceptors). ● has cell bodies in the inferior (petrosal) ganglion. ● the afferent limb of the gag reflex and the carotid sinus reflex. 3. ● innervates the taste buds of the posterior third of the tongue. ● has cell bodies in the inferior (petrosal) ganglion. ● projects its central processes to the solitary tract and nucleus. College of Medicine – كلية الطب Glossopharyngeal (IX) 4. ● innervates the stylopharyngeus. ● arises from the nucleus ambiguus of the lateral medulla. 5. ● a parasympathetic component that innervates the parotid gland. ● consists of preganglionic neurons in the inferior salivatory nucleus of the medulla that project, via the tympanic nerve and the lesser petrosal nerve to the otic ganglion; postganglionic fibers from the otic ganglion project to the parotid gland via the auriculotemporal nerve (CN V3) GLOSSO-PHARYNGEAL NERVE (9TH CRANIAL NERVE ) inf. cerebellar peduncle Nuclei: College of Medicine – كلية الطب -Nucleus ambiguus (A) 1 -Nucleus dorsalis (B) -Nucleus solitarius (C) -Inferior salivary nucleus (D) pons the n. in groove between olive and inf. cerebellar peduncle 2 1 medulla 4 3 6 2 ganglia olive glosso- pharyngeal n. tongue 8 5 9 Course of glosso-pharyngeal nerve (9th cranial nerve) 7 site of hyoglossus m. College of Medicine – كلية الطب BRANCHES OF GLOSSOPHARYNREAL NERVE College of Medicine – كلية الطب 1.Tympanic nerve: 2. Nerve to stylopharyngeus. 3.Pharyngeal branches. 4.Carotid nerve . c d f b ganglia1 e a 6 glossopharyngeal n. tongue 2 5.Terminal branches. 5 4 3 College of Medicine – كلية الطب Glossopharyngeal (IX) Clinical correlations: lesions of CN IX 1. Loss of the gag (pharyngeal) reflex (interruption of afferent limb) 2. Loss of the carotid sinus reflex (interruption of the sinus nerve) 3. Loss of taste from the posterior third of the tongue 4. Glossopharyngeal neuralgia College of Medicine – كلية الطب Vagus (X) General characteristics of CN X ● mediates phonation, swallowing (with CN IX and CN XII), elevation of the palate, and taste. ● innervates viscera of the neck, thorax, and abdomen. ● the nerve of the fourth and sixth branchial arches. ● exits the brainstem (medulla) from the postolivary sulcus. ● exits the skull via the jugular foramen with CN IX and CN XI. College of Medicine – كلية الطب Vagus (X) 1. ● innervates the infratentorial dura (with C2 and C3) external ear, external auditory meatus, and tympanic membrane ● has cell bodies in the superior (jugular) ganglion. ● projects its central processes to the spinal trigeminal tract and nucleus. 2. ● innervates the mucous membranes of the pharynx, larynx, esophagus, trachea, and thoracic and abdominal viscera (to the mid-transverse colon). ● has cell bodies in the inferior (nodose) ganglion. ● projects its central processes to the solitary tract and nucleus. College of Medicine – كلية الطب Vagus (X) 3. ● innervates the taste buds over the epiglottis and soft palate. ● has cell bodies in the inferior (nodose) ganglion. ● projects its central processes to the solitary tract and nucleus. 4. ● innervates the pharyngeal arch muscles of the larynx and pharynx, striated muscle of the upper esophagus, musculus uvalae, and levator palati and palatoglossus. ● arises from the nucleus ambiguus in the lateral medulla. ● provides the efferent limb of the gag reflex. College of Medicine – كلية الطب Vagus (X) 5. ● innervates the viscera of the neck and the thoracic and abdominal cavities as far as the mid-transverse colon. ● consists of preganglionic parasympathetic neurons in the dorsal motor nucleus of the vagus, which project to the intramural ganglia of the viscera. College of Medicine – كلية الطب Vagus (X) Clinical correlations: lesions of CN X ● result in the following conditions: 1. Ipsilateral paralysis of the soft palate, pharynx, and larynx leading to dysphonia (hoarseness), dyspnea, dysarthria, and dysphagia 2. Loss of the gag (palatal) reflex (efferent limb) 3. Anesthesia of the pharynx and larynx, leading to unilateral loss of the cough reflex 4. Aortic aneurysms and tumors of the neck and thorax ● frequently compress the vagal nerve. College of Medicine – كلية الطب X : Vagus Nerve College of Medicine – كلية الطب It is mixed nerve, attached lateral to olive of medulla caudal to glossopharyngeal N. in groove between olive & inf.cerebellar peduncle. It recevies afferent Fs.from : 1-Receptors for general sensation in pharynx, larynx, tympanic membrane, ext.acoustic meatus. 2-Chemoreceptors in aortic bodies and baroreceptors in aortic arch. 3-Receptors in thoracic & abdominal viscera. College of Medicine – كلية الطب X : Vagus Nerve Fibres : 1-Afferent Fs.for general sensation : end in sensory nucleus of trigeminl and - visceral sensory afferents end in nucleus solitarius. 2-Efferent Motor Fs. : arise from nucleus ambiguus of medulla (main motor nucleus of vagus) to innervate Ms. of soft palate, pharynx, larynx to control swallowing and speech. 3-Efferent Parasymp. Fs. : arise from dorsal nucleus of vagus to supply CVS,RS,& GITS. VAGUS NERVE vagus 1 3 Nuclei : 4 nuclei in the medulla -Nucleus ambiguus (A) College of Medicine – كلية الطب -Nucleus dorsalis (B) pharyngeal br. -Nucleus solitarius (C) -Spinal tract and nucleus of trigeminal nerve (D) carotid br. sup. laryngeal C B 2 Inf. cerebellar peduncle recurrent laryngeal A medulla vagus n. 4 olive pyramid D 5 COURSE OF VAGUS n. BRANCHES OF VAGUS NERVE vagus n. 1. Meningeal branch. 2. Communicating branches. 3. Auricular branch. 1 College of Medicine – كلية الطب 4. Pharyngeal branch. 3 5 .Superior laryngeal nerve which divides into: a.External laryngeal nerve 4 (motor) b.Internal laryngeal nerve (sensory) 5 6. Carotid branch 7. Cardiac branches. 8. Right recurrent laryngeal nerve. R.L.N R.L.N 6 7 8 S College of Medicine – كلية الطب Accessory (XI) (spinal accessory) General characteristics of CN XI ● not actually a cranial nerve, as it originates in the spinal cord. ● mediates head and shoulder movement. ● arises from the anterior horn of cervical segments C1 to C6. ● spinal roots exit the spinal cord laterally between the anterior and posterior roots, ascend through the foramen magnum, and exit the skull via the jugular foramen. ● innervates the sternocleidomastoid (with C2) and trapezius (with C3 and C4). College of Medicine – كلية الطب B. Clinical correlations: lesions of CN XI ● result in the following conditions: 1. Paralysis of the sternocleidomastoid muscle ● results in difficulty in turning the head to the side opposite the lesion. 2. Paralysis of the trapezius muscle ● results in a shoulder droop. ● results in the inability to shrug the ipsilateral shoulder. 51 ACCESSORY NERVE medulla College of Medicine – كلية الطب the cranial root joins the vagus foramen magnum 7 6 ACCESSORY NERVE CRANIAL PART SPINAL PART trapezius 10 College of Medicine – كلية الطب Hypoglossal (XII) General characteristics of CN XII ● mediates tongue movement. ● arises from the hypoglossal motor nucleus of the medulla. ● exits the medulla in the preolivary sulcus. College of Medicine – كلية الطب Hypoglossal (XII) exits the skull via the hypoglossal canal. ● innervates intrinsic and extrinsic muscles of the tongue. B. Clinical correlations: CN XII ● When it is transected, hemiparalysis of the tongue results. ● The tongue points toward the weak side due to the unopposed action of the opposite genioglossus upon protrusion. College of Medicine – كلية الطب XII : Hypoglossal Nerve It is purely motor , supplying all extrinsic & intrinsic Ms. of tongue except palatoglossus (by pharyngeal plexus). It arises from hypoglossal nucleus in medulla ( beneath floor of 4th V.). It emerges from M.O. between olive & pyramid. It also receives coticobulbar Fs. from contralateral motor cortex to supply Ms. of tongue for speech. HYPOGLOSSAL NERVE College of Medicine – كلية الطب Nucleus: Hypoglossal nerve nucleus (A) 9 COURSE OF HYPOGLOSSAL NERVE College of Medicine – كلية الطب BRANCHES OF HYPOGLOSSAL NERVE The first cervical (C1) gives a contribution to the hypoglossal nerve which gives the branches of hypoglossal nerve. hypoglossal n. 4genio- glossaus hypoglossal canal tongue medulla 1. Descendens hypoglossi (1) hyoglossus m. 3 2. Nerve to thyrohyoid (2) 3. Nerve to geniohyoid (3) 2 1 4. The pure hypoglossal nerve fibers supply the intrinsic and extrinsic muscles of tongue (4) (except the palatoglossus). descendens cervicalis descendens hypoglossi ansa cervicalis thyrohyoid m. College of Medicine – كلية الطب References • Clinical Neuroanatomy for Medical Students, Richard S. Snell-6th Edition. • Clinical Neuroanatomy and related neuroscience. M.J.T. FitzGerald, Jean Folan-Curran, Fourth Edition. • Crossman, AR and Neary D, Neuroanatomy: An Illustrated Colour Text. • Haines, DE, Neuroanatomy: An Atlas of Structures, Sections and Systems. • Agur, A. M. R. and A. F. Dalley. 2009. Grant’s Atlas of Anatomy, 12th Edition. Lippincott, Williams & Wilkins, New York. • Moore, K. L., A. F. Dalley and A. M. E. Agur. 2010. Clinically Oriented Anatomy, 6th Edition. Lippincott, Williams & Wilkins, New York. • Sadler, T. W. 2004. Langman’s Medical Embryology, 9th Edition. Lippincott, Williams & Wilkins, New York.