BMS2-8 Cranial Nerves - CN VII.- Dr. Aylin AKTAR pdf.pdf

Cranial Nerve VII - Facial Functions: • Sensory: Special sensory (taste) & somatic (general) sensory • Motor: Somatic (branchial) motor & visceral (parasympathetic) motor • All nuclei at pons level • Leaves brain stem from pontobulbar sulcus (sulcus bulbopontinus) Nuclei: (1) Facial nucleus - main...

Cranial Nerve VII - Facial Functions: • Sensory: Special sensory (taste) & somatic (general) sensory • Motor: Somatic (branchial) motor & visceral (parasympathetic) motor • All nuclei at pons level • Leaves brain stem from pontobulbar sulcus (sulcus bulbopontinus) Nuclei: (1) Facial nucleus - main motor nucleus (2) Parasympathetic nuclei (3) Sensory nucleus – upper part of solitary nucleus 1 Cranial Nerve VII - Facial Parts: • Intracranial: Before it enters the temporal bone • Intratemporal Inside temporal bone • Extratemporal After it exits the temporal bone 2 Cranial Nerve VII - Facial Intracranial Course • Emerges from junction of pons & medulla as 2 divisions: the primary root & the intermediate nerve Primary root: • Larger • Facial nerve proper • Innervates muscles of facial expression Smaller root: • A.k.a. intermediate nerve (L. nervus intermedius) • Sensory & PS part of facial n. • Carries taste, parasympathetic, & somatic sensory fibers 3 Cranial Nerve VII - Facial Main Motor Nucleus (Nucleus Nervi Facialis) • Somatic motor fibers • Muscles of facial expression, buccinator, platysma, stapedius, stylohyoid, post. belly of digastric m.m. • Part of nucleus that supplies muscles of upper part of face receives corticonuclear fibers from both cerebral hemispheres • Part of nucleus that supplies muscles of lower part of face receives corticonuclear fibers only from opposite cerebral hemisphere • Another ‘involuntary’ pathway exists; it is separate & controls mimetic or emotional changes in facial expression • This other pathway forms part of reticular formation 4 Cranial Nerve VII - Facial Sensory Nucleus • Receives taste fibers from ant. 2/3rds of tongue, floor of mouth, & palate + general sensation • Is upper part of nucleus of the tractus solitarius a.k.a solitary nuc. • Sensations of taste travel thru peripheral axons of neurons of geniculate ganglion – intermediate nerve 5 Cranial Nerve VII - Facial Parasympathetic Nuclei Superior Salivatory nucleus: • At dorsal pons (pontine tegmentum) • Supplies submandibular, sublingual, nasal & palatine glands • Info re. taste sent to nucleus of the solitary tract from oral cavity Lacrimal nucleus: • Is a portion of superior salivatory nucleus • Supplies lacrimal gland • Receives afferent fibers from hypothalamus for emotional responses & from the sensory nuclei of trigeminal nerve for reflex lacrimation secondary to irritation of cornea or conjunctiva. 6 Solitary Nucleus • Series of purely sensory nuclei • Forms vertical column of grey matter • Embedded in medulla oblongata • Through its center runs the solitary tract: white bundle of nerve fibers • Includes fibers from facial n., glossopharyngeal n. & vagus nerves that innervate the solitary nucleus 7 Cranial Nerve VII - Facial Nuclei 8 Cranial Nerve VII - Facial Facial Colliculus 9 Cranial Nerve VII - Facial . 10 Cranial Nerve VII - Facial Intracranial Course • The 2 roots emerge from ant. surface of brain btwn pons & medulla oblongata (pontobulbar sulcus) • Pass laterally in post. cranial fossa w/vestibulocochlear n. 11 Cranial Nerve VII - Facial Course • Pierces dura & arachnoid covering internal acoustic meatus & enters facial canal • Turns abruptly posteriorly to course along medial wall of tympanic cavity • The sharp bend, geniculum of facial n. is site of geniculate ganglion, sensory ganglion of CN VII • Descends & exits temporal bone thru stylomastoid foramen 12 13 14 Cranial Nerve VII - Facial Branches Given off in Temporal Bone • Greater petrosal n. • N. to stapedius m. (motor) • Chorda tympani 15 Cranial Nerve VII - Facial Course • Within facial canal – at the geniculum, gives off greater petrosal n. 16 Cranial Nerve VII - Facial Branches Given off in Facial Canal Greater Petrosal Nerve (a.k.a. superficial petrosal n.) • Contains taste fibers from palate • Contains PS fibres destined for pterygopalatine ganglion → Greater petrosal foramen → Foramen lacerum • Enters pterygoid canal • Joins deep petrosal n (sympathetic) in pterygoid canal → forms n. of pterygoid canal (a.k.a. Vidian n.) • Synapses on pterygopalatine ganglion Secretomotor to: • Lacrimal gland • Nasal glands • Small salivary glands 17 PS Innervation of Lacrimal Gland • • Post ganglionic fibres from pterygopalatine ganglion (derived from facial n.), travel with zygomatic branch of V2 & then join lacrimal branch of V1. The fibres supply parasympathetic innervation to the lacrimal gland 18 Cranial Nerve VII - Facial Nasal glands: Parasympathetic fibres also carried to the mucous glands of nasal mucosa Post-ganglionic fibres from pterygopalatine ganglion travel with the nasopalatine n. & greater palatine n. (branches of V2) 19 20 Cranial Nerve VII - Facial Branches Given in Facial Canal Chorda Tympani • Exits thru petrotympanic fissure → enters infratemporal fossa • Carries taste from ant. 2/3rd of tongue – special sensory functiom • Geniculate ganglion contains cell bodies for taste • Courses within lingual n. • Carries PS fibers to submandibular ganglion • Secretomotor innervation via postsynaptic PS fibers to submandibular & sublingual glands 21 Cranial Nerve VII - Facial Branches After Exit From Facial Canal • Post. auricular n. - motor → runs upward in front of mastoid process → → divides into auricular & occipital branches • Digastric branch – to post belly of digastric m. - motor • Stylohyoid branch – motor • Then it enters substance of parotid gland 22 Cranial Nerve VII - Facial Enters Parotid Gland • Enters parotid gland & branches out within • Variations common • 2 chief divisions generally exist: Temporofacial & cervicofacial o Temporal branch o Zygomatic brach o Buccal branch : Branches run above & below parotid duct o Mandibular branch (a.k.a. marginal mandibular) o Cervical branch 23 Cranial Nerve VII - Facial Branches given within substance of parotid gland Branches given after exit from stylomastoid foramen and before entering the substance of parotid gland 24 Cranial Nerve VII - Facial Enters Parotid Gland 25 Cranial Nerve VII - Facial Enters Parotid Gland Medial pterygoid m. Masseter Parotid gland Facial n. 26 27 Cranial Nerve VII - Facial . 28 Main Gyri: Cerebrum • Precentral gyrus – ridge directly ant. to central sulcus, location of primary motor cortex • Postcentral g – ridge directly post. to central sulcus, location of primary somatosensory cortex • Superior temporal gyrus – ridge located inf. to lateral sulcus, responsible for reception and processing of sound • Location of upper motor neurons Cranial Nerve VII - Facial Central Facial Paralysis • Supranuclear levels of facial n. damage – upper motor neuron (UMN) • Signs seen below eyes on contralateral side • Especially affected are perioral muscles • Mouth deviates to unaffacted side • Part of motor nucleus that supplies muscles of upper part of face receives corticonuclear (a.k.a. corticobulbar) fibers from both cerebral hemispheres • Part of motor nucleus that supplies muscles of lower part of face receives corticonuclear fibers only from opposite cerebral hemisphere 30 Cranial Nerve VII - Facial Bell’s Palsy • A lower motor neuron facial palsy Signs: 1-Paralysis of mm. of expression on the lesion side (ipsilateral) and depending on exact location of lesion, may have: 2-Hyperacusis (decreased tolerance to loud noises) 3-Loss of cornea reflex (Facial n. is efferent limb of corneal reflex) 4-Function of lacrimal & salivary glands impaired 5-Loss of taste sensation on ant. 2/3 of tongue 31 Normal innervation of R side of face R central lesion L peripheral lesion Cranial Nerve VII - Facial Other Potential Injuries in its Extratemporal Course • During surgery involving the parotid gland, submandibular glands, TMJ • During facelift surgery • Facial trauma & laceration 33 Cranial Nerve VII Facial . 34