1. Facial and Hypoglossal nerves D.Nimer D.Rania Gabr D.Safaa D.Elsherbiny

2. Objectives Describe the nuclei of the facial nerve Follow up the course of facial nerve from its point of central connections, exit and down to its target areas. Discuss the various modalities of its fibers. Review your knowledge of its target areas Follow up the course from the central connections; exit from the brain and down to its target organs of XII nerves Make a list of types of nerve modalities conveyed by this nerve.

3. Functional Components of Peripheral Nerves Spinal Nerves General somatic afferents (GSA) General somatic efferents (GSE) General visceral afferents (GVA) General visceral efferents (GVE) All spinal nerves carry all the four components Cranial Nerves GSA GSE GVA GVE Special somatic afferents (SSA) Special visceral afferents (SVA) Special visceral efferents (SVE) NOT all cranial nerves carry all these components

4. FACIAL NERVE Type: Mixed ( Motor, special sensory, parasympathetic Origin: It arises by two roots, motor root and nervus intermedius: 1. Motor root (large and medial): from the motor nucleus of the facial nerve in the pons. 2. Nervus intermedius (small and lateral): contains sensory & parasympathetic fibers. 2 1

5. Fiber Contents and their Origin: 1. Motor fibers: from the motor nucleus in the pons to the muscles of the second pharyngeal arch. 2. Sensory (taste) fibers: from the anterior 2/3 of the tongue to the nucleus solitarius in the medulla oblongata. 3. Parasympathetic secretomotor fibers: from the superior salivatory nucleus in the pons to the: a. Lacrimal, nasal and palatine glands: through the greater superficial petrosal nerve and the pterygopalatine ganglion. b. Submandibular and sublingual salivary glands: through the chorda tympani nerve and the submandibular ganglion.

6. COURSE OF FACIAL NERVE Exit from the Brain: in the cerebellopontine angle. Exit from the Cranial Cavity: through the internal auditory meatus, where the 2 roots unite at the bottom of the meatus. Course inside the skull: it passes in the bony facial canal in the petrous part of the temporal bone along the medial wall of the middle ear. Exit from the Skull: through the stylomastoid foramen. Course Outside the Skull (Extracranial Part): Enters the parotid gland, where it is the most superficial structure and divides into 5 terminal branches.

7. Has five intracranial segments: 1.Nucleus facialis and pontine segment. 2.Intracanalicular segment (Meatal) 3.Labyrinthine segment 4.Tympanic segment (horizontal) 5.Mastoid segment (vertical) Then its emerges from the (stylomasotid foramen) and gives the extra-cranial segment COURSE OF FACIAL NERVE

9. Intracranial Branches of Facial Nerve  In facial canal: 1-Greater petrosal nerve: carries preganglionic parasympathetic fibers to lacrimal, nasal & palatine glands. 2-Nerve to stapedius. 3-Chorda tympani: carries: a) Preganglionic parasympathetic fibers to the submandibular & sublingual glands. b) Taste fibers from the anterior 2/3 of tongue. N.B.: Geniculate ganglion: lies in internal acoustic meatus, contains cell bodies of neurones carrying taste sensations from anterior 2/3 of tongue.

11. The extra-cranial part branches 1. Posterior auricular nerve: (auricularis posterior and occipitalis) 2. Branches to the post belly of the digastric and the stylohyoid muscles 3. Five terminal branches : within the substance of the parotid gland to the muscles of the face 1.Temporal 2.Zygomatic 3.Buccal 4.Mandibular 5.Cervical

14. 1.Upper motor neuron lesion:  lesion in the corticobulbar tract  It causes paralysis of the lower half of the opposite facial nucleus and paralysis of the muscles of the lower half of the opposite side of the face. 2.Lower motor neuron lesion:  lesion in the facial nerve or the facial nucleus  It causes flaccid paralysis of all muscles of facial expression on the same side of the face. The lesion may be located at any level: I.In the facial colliculus, where it is accompanied by abducent nuclear lesion. II.In the basis pontis: accompanied by hemiplegia (paralysis of one 1/2 of the body). III.At the cerebellopontine angle, where it is accompanied by VIII lesion. IV.At the facial canal or the stylomastoid foramen (Bell s palsy). Lesion of Facial nerve

16. Bell’s Palsy Damage to facial nerve results in paralysis of muscles of facial expressions : Facial (Bell’s palsy); lower motor neuron lesion (whole face affected) NB. In upper motor neuron lesion (upper face is intact).

17. The signs are present on the same side of the face: 1.Paralysis of the frontalis: inability to raise the eyebrow. 2.Paralysis of the orbicularis oculi: inability to close the eye, which remains open and loss of the corneal reflex. 3.Paralysis of the orbicularis oris: inability to whistle. 4.Paralysis of the levators of the angle of the mouth: drooping of the angle of the mouth. 5.Paralysis of the buccinator: accumulation of food in vestibule of the mouth. 6.Paralysis of the stapedius: hyperacusis (hypersensitivity to sounds). 7.Paralysis of the chorda tympani: loss of taste sensation from the anterior two-thirds of the tongue and decreased salivation. 8.Paralysis of the greater superficial petrosal nerve: loss of lacrimation. Signs of the Lower Motor Neuron Lesion

18. Facial nerve paralysis Upper motor neuron lesions Involvement of the pyramidal tract The upper part of the face stays normal because the neurons supplying this part of the face receive corticobulbar fibers from both cerebral cortices.

19. Type: motor nerve. Origin: Hypoglossal nucleus in the medullary part of the floor of the 4th ventricle. Exits from the Brain: in the preolivary fissure (between the pyramid and the olive) Exits from the Skull: through the hypoglossal canal. 12 th CN: Hypoglossal Nerve

20. Course:  Just below the skull, it is joined by a branch from the first cervical nerve.  It descends in the carotid sheath between the internal jugular vein and internal carotid artery.

21. C1 fibers  In the submandibular region, it lies superficial to the hyoglossus below the lingual nerve and the submandibular duct → it terminates by entering the tongue.

22. EXCEPT The hypoglossal nucleus receives corticonuclear fibers from both cerebral hemispheres EXCEPT the region that supplies genioglossus muscle (it receives contralateral supply only) Also receives afferent fibers from nucleus solitarius and trigeminal sensory nucleus.

23. 1. From the Hypoglossal Nerve Itself: Muscular branches to all the intrinsic and extrinsic muscles of the tongue except the palatoglossus muscle (supplied by the vagus). 2. From the First Cervical Nerve (C1): a. Meningeal branch: supply the dura of the posterior cranial fossa. b. Superior root of ansa cervicalis (descendens hypoglossi): unites with the inferior root (descendens cervicalis, C2 & 3) forming the ansa cervicalis, which supplies all the infrahyoid muscles except the thyrohyoid (omohyoid, sternohyoid and sternothyroid). c. Nerve to thyrohyoid: to the thyrohyoid muscle. d. Nerve to geniohyoid: to the geniohyoid muscle. Branches and Distribution:

24. Normal LESION  LMN paralysis of the same side of the tongue (hemiparalysis).  Deviation of the protruded tongue toward the affected side. Lesion of the nerve results into: – Loss of tongue movements – Difficulty in chewing and speech – The tongue paralyses, atrophies, becomes shrunken and furrowed on the affected side (LMN paralysis) – On protrusion, tongue deviates to the affected side If both nerves are damaged, person can’t protrude tongue