FACIAL NERVE FINAL 6THCRANIAL NERVE.pptx

6TH CRANIAL NERVE IN DETAIL

1. FACIAL NERVE PRESENTED BY:- DR.AISHWARY SINGH SANTOSH MEDICAL COLLEGE

2. INTRODUCTION S eventh cranial nerve. contains the motor, sensory, and parasympathetic ( secretomotor ) nerve fibers provide innervation to many areas of the head and neck region. Emerges from brainstem between pons and medulla

3. MOTOR PATHWAY Superanuclear neurons destined to supply facial nerve nucleus are located precentral gyrus of frontal lobe . As the fibres descend down to corticobulbar tract , in middle of internal capsule ,decussate just below midbrain to cross opposite side of pons to supply most of opposite sie of facial nerve, but at the same time some fibres are also supplied by the ipsilateral facial nucleus

4. So in supranuclear lesion ,upper part of face is spared, as it receives supply from ipsilateral and contralateral supranuclear neurons Nuclear/ infranuclear lesions , entire hemiface involved

5. Infra nuclear lesion of facial nerve is called Bell’s Palsy Complete lesion of facial nerve as it emerges from stylomastoid foramen results in : a) Complete paralysis of facial muscles of same side b) Drooping of angle of mouth c ) Flat nasolabial fold d ) Dribbling of saliva from same side e ) Loss of corneal reflex

6. NUCLEI OF FACIAL NERVE : major bulk formed by motor nucleus 4-

7. NUCLEI AND BRAINSTEM TRACTS FACIAL NUCLEUS  (motor) ​ in the ventrolateral pontine tegmentum , giving off fibers that loop posteriorly over the  abducens nerve  nucleus, which together form the  facial colliculus  in the floor of the  fourth ventricle supplies motor fibers to the  stapedius  and  muscles of facial expression SUPERIOR SALIVARY NUCLEUS  (parasympathetic) in the pons,  ​ medial to the facial nucleus supplies secretomotor   parasympathetic   fibers to  lacrimal ,  submandibular , and  sublingual glands

8. SOLITARY NUCLEUS  (taste) in the medulla and lower pons,  ​ lateral to the dorsal nucleus of the  vagus nerve receives taste fibers from the anterior  tongue  via the  chorda tympani SPINAL NUCLEUS OF THE TRIGEMINAL NERVE  (somatic sensory) ​ in the upper cervical spinal cord, medulla, and pons, ventral to the  vestibular  and  cochlear nuclei receives somatosensory fibers from the posterior  external auditory canal

9. COURSE INTRACRANIAL PART INTRAMEATAL PART LABYRINTHINE SEGMENT TYMPANIC SEGMENT MASTOID SEGMENT EXTRACRANIAL PART

10. INTRACRANIAL comprised of a motor root (containing motor fibers /facial nerve proper) and the nervus intermedius (containing sensory and parasympathetic fibers ).

11. The axons from the motor nucleus curve posteriorly around the abducent nucleus form sight bulge in floor of fourth ventricle called facial colliculus and , finally, emerge as facial nerve from the ventro -lateral brainstem.

12. The nervus intermedius of the facial nerve also emerges from the ventrolateral brainstem ( pontomedullary junction) At the cerebropontine angle facial nerve emerges out with 8 th nerve A nterior inferior cerebellar artery (AICA) supplies this part of pons , loops across facial and 8 th nerve A neurysm of this artery /close contact with nerve can cause H emifacial spasm

13. INTRAMEATAL Enters petrous part of temporal bone Accompanied by cranial nerve VIII, the facial nerve travels through the internal auditory canal to antero -superior part medial wall of middle ear motor fibre bend at genu( bend) ganglion and move backward through bony facial canal and then turn downward on reaching posterior wall of middle ear

14. Bony canal opens in stylomastoid foramen and facial nerve proper exits giving branches to stapedius muscle in posterior wall while moving downwards posterior auricular branch branch to stylohyoid posterior belly of digastric and then to parotid gland dividing in 5 branches T emporal Z ygomatic B uccal Marginal mandibular Cervical

15. The temporal and zygomatic branches of the facial nerve supply the orbicularis oculi, the main eyelid protractor . The facial nerve also supplies the corrugator supercilii and the procerus , both of which contribute to brow depression and secondarily contribute to upper eyelid protraction.

16. RAMSAY HUNT SYNDROME Herpes zoster oticus , L ate complication of varicella-zoster virus infection that results in inflammation of the geniculate ganglion of cranial nerve VII. Triad of I psilateral facial paralysis Otalgia Vesicles near the ear and auditory canal

17. BRANCHES IN FACIAL CANAL Pre ganglionic Parasympathetic fibre( salivatory and lacrimatory fibre) enter internal auditory meatus , reach geniculate ganglia , and then separate The parasympathetic fibres of the facial nerve are carried by the  greater petrosal  and  chorda tympani  branches . Lacrimatory fibre , distal to the  geniculate ganglion now called greater petrosal nerve   move in anteromedial direction exiting the temporal bone into middle crania fossa

18. From here it travels across foramen lacerum and are joined by Deep petrosal nerve ( sympathetic fibres from plexus around ICA) collectively now called nerve to pterygoid canal/ vidian nerve , move in pterygoid canal and reach pterygopalatine fossa and synapse with pterygopalatine ganglia P os t ganglionic b ranches from this ganglion then go on to provide parasympathetic innervation to the  mucous glands  of the oral cavity, nose and pharynx, and the  lacrimal gland .

19. Salivatory fibres with facial nerve proper move in facial canal , turn to reach middle ear cavity to be called called chorda tympani nerve These combine with the  lingual nerve  (a branch of the trigeminal nerve) in the   infratemporal fossa   and form the   submandibular ganglion . Branches from this ganglion travel to the submandibular and sublingual  salivary glands Sensory fibre (taste fibre) from nucleus of tractus solitarius follow the same path and reach to anterior 2/3 rd of tongue

20. Xerotic Keratitis Rare consequence of greater petrosal nerve damage is reduced tear secretion, called xerotic keratitis, which can lead to extreme dryness of the eyes, ulceration of the cornea, and blindness. Crocodile Tears Syndrome Lesions on the facial nerve ( Bell’s palsy ) can cause degeneration of the greater petrosal nerve . In some cases, the lesser petrosal nerve sometimes takes over the innervation of the lacrimal glands . Because the lesser petrosal nerve also innervates the salivary gland, salivation causes simultaneous eye watering.

21. Cluster Headaches Parasympathetic dysfunction involving the greater petrosal nerve can cause  cluster headaches . cause excessive eye watering, nasal congestion, and runny nose .

22. BLOOD SUPPLY L abyrinthine artery : a branch of the  anterior inferior cerebellar artery (AICA) , supplies the meatal segment. S uperficial petrosal artery : a branch of the  middle meningeal artery  which passes retrogradely along the  greater superficial petrosal nerve S tylomastoid artery : a branch of the  posterior auricular artery , which passes retrogradely into the  stylomastoid foramen

23. OPHTHALMIC CONSIDERATIONS

24. FACIAL NERVE BLOCK Van lint O'Brien Technique Nadbath and rehman Atkinson Upper and lower eyelid block AIM-Blocking action of orbicularis

25. Upper and Lower Eyelid Blocks I nfiltration of local anesthesia directly into the eyelids to achieve akinesia of the orbicularis oculi. The upper eyelid block is completed at 1cm above the medial canthus lower eyelid block is performed 0.5 cm below the medial canthus .  The lid block has been shown as a highly effective proximal block of the facial nerve without bearing the risks of direct nerve root trauma

26. FACIAL NERVE PALSY

27. Common causes

28. EVALUATION History Onset and duration History of prior injury (head trauma can damage temporal bone H /o facial/ear surgery Congenital facial palsy mostly involves motor component so patient have good tear secretion Middle ear diseases Associated pain –bells palsy/herpes zoster Hyperacusis symptom(damage to nerve to stapedius )

29. Continued…. Decreased taste sensation(chorda tympani involvement) Symptoms of other cranial nerve :numbness of face , diplopia, anosmia,difficult swallowing H /o DM Recent immunization –polio /influenza H /o periaural rash- ramsay hunt syndrome

30. SYMPTOMS Inability to close eyes( lagophthalmos ) Irritation Eye pain Chronic red eye Ectropion Drooping of brow

31. EXAMINATION Visual acuity Muscles of facial expression(masked face in b/l lesion , unilateral lesion – lmn – hemiface on side of lesion looses muscle tone Frontalis muscle( supranuclear /nuclear / infranuclear ) Lid closure Upper lid retraction retraction Tear film (greater petrosal nerve ) Lower lid- ectropion / punctal position Corneal sensation (5 th nerve) Corneal staining B ell’s phenomena

32. CONTINUED… Ocular motility Hearing Palpate parotid gland Regional lymph nodes

33. CLINICAL DIAGNOSIS H istory and physical examination Bell’s Palsy is a diagnosis of exclusion . C hronicity , severity, and laterality of the palsy P rimary or secondary P roximal or distal lesion . M ost widely used scale is House- Brackmann scale.However , the only ophthalmic manifestation of facial nerve palsy assessed in this scale is eye closure. currently , there is no universal scale available to document the complete spectrum of ophthalmic presentations of facial nerve palsy

34. MANAGEMENT Age of patient Occupation Ability to comply treatment

35. GENERAL CONSIDERATION Risk of exposure and corneal ulceration Absent corneal sensation Severe lagophthalmos Absent bells phenomena Dry eye

36. MEDICAL MANAGEMENT P rotect and lubricate the cornea to prevent  exposure keratopathy . A rtificial tears and artificial tear gel at bedtime for lagophthalmos . Taping of eyelids and application petroleum-jelly based lubricating ointment Punctal plugs  may be useful for persistent dry eyes .  Lower lid ectropion can be managed by applying tape to the lower lid.

37. Transconjunctival injection of botulinum toxin into the upper lid can weaken the levator palpebrae superioris and induce ptosis of the upper lid to protect the corneas O ral steroids within 72 hours of symptom onset in Bell's palsy B otulinum toxin to improve brow position or asymmetric frontalis action, to address ocular synkinesis

38. SURGICAL TREATMENT To reduce lagophthalmos , implantation of a gold or platinum weight in the upper eyelid Surgical treatment of upper lid retraction includes Mullerectomy for 1-3 mm of retraction, and levator recession or levator-mueller's muscle recession for retraction > 3 mm . Paralytic ectropion addressed using lateral tarsal strip procedure with an additional posterior lamellar spacer graft for more severe cases .   TARSORRHAPHY laterally and/or medially

39. Conjunctivodacryocystorhinostomy ( cDCR ) surgery with Jones tube in impaired lacrimal pump function and weakened orbicularis oculi . S urgical correction of paralytic brow ptosis and face lift or facial sling

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