Facial Nerve Paralysis

1. Facial Nerve Paralysis Dr. Vishal Sharma

2. Gabriel Fallopius (1523-62)

3. Anatomy of Facial Nerve • Motor root:7000 axons • Sensory root (Nervus intermedius / Wrisberg): 3000 axons. Joins motor root at fundus of I.A.C. • Motor:predominantly to facial muscles • Secretomotor:lacrimal, submandibular, sublingual • Taste:anterior 2/3rd of tongue • Sensory:Post-aural / concha / ext. auditory canal

4. Course of facial nerve

10. Parts of facial nerve Intracranial: within cerebello-pontine angle Intra-temporal  Meatal segment  Labyrinthine segment  Tympanic segment  Mastoid segment Extra-cranial  Extra-parotid  Intra-parotid (terminal)

11. Segments of Facial Nerve 1. Supranuclear:Fibers in cerebral cortex to brain stem 2. Brain stem:Motor nucleus of facial nerve (pons) 3. Intra-cranial (12 mm): Brain stem to entry into IAC 4. Meatal (10 mm):Within Internal Auditory Canal 5. Labyrinthine (4 mm):Fundus of I.A.C. to Geniculate gangl. 6. Tympanic (11 mm):Geniculate ganglion to pyramid 7. Mastoid (13 mm):Pyramid to stylomastoid foramen 8. Extra-temporal (15 mm):S.M. foramen to pes anserinus

12. Primary branches of facial nerve Intra-temporal: greater superficial petrosal, stapedius, chorda tympani Extra-parotid:post-auricular, stylohyoid, posterior belly of digastric Intra-parotid: temporal, zygomatic, buccal, marginal mandibular, descending cervical

13. Intra-cranial branches

14. Extra-cranial branches

15. Communicating branches to: Meatal: vestibulo-cochlear Tympanic: lesser petrosal  otic ganglion Mastoid: auricular branch of vagus Extra-parotid: glossopharyngeal, auriculotemporal, vagus, greater auricular, lesser occipital Terminal: branches of trigeminal

16. Surgical landmarks

17. Cochleariform process:small bony protuberance (from which tensor tympani muscle turns 900 to insert into malleus) lies 1 mm inferior to geniculate ganglion at anterior end of tympanic segment. Cog: bony ridge hanging from tegmen tympani lies 1 mm above & posterior to cochleariform process. Incusshort process:2 mm below lies external genu Lateral Semicircular Canal: 2 mm Antero-Infero-Medial lies external genu Oval window:1 mm above lies external genu

18. Inferior edge of Posterior S.C.C.:2 mm anterior & lateral lies mastoid segment of facial nerve Tympano-mastoid suture in posterior canal wall:5-8 mm medial lies mastoid segment of facial nerve Digastric ridge in mastoid tip:leads antero-medially to mastoid segment of facial nerve Groove between mastoid & bony E.A.C. meatus: bisected by facial nerve Tragal pointer:1 cm antero-infero-medial is facial nv Root of styloid process: lateral lies facial nerve Superior border of posterior belly of digastric: superior & parallel lies facial nerve

19. Surgical landmarks

20. Lesions of Facial Nerve

25. Etiology of Facial Nerve Palsy

26. 1. Idiopathic (55%):Bell’s palsy, Melkersson Rosenthal syndrome 2. Temporal bone trauma (25%): Road traffic accident 3. Infection (10%):C.S.O.M., Herpes Zoster oticus Malignant otitis externa 4. Neoplasm (5%): Parotid tumors, Acoustic Neuroma, Glomus tumors, Malignancy of ear 5. Congenital (4%):Moebius syndrome 6. Iatrogenic (rare): Mastoidectomy, Parotid surgery 7. Metabolic (rare):Diabetes mellitus, Hypertension

27. Sunderland’s Classification (1951)

28. Cross section of nerve

31. House Brackmann Classification (1 year post-injury)

34. Diagnosis • Topo-diagnostic Tests • Electrical Tests • Magnetic stimulation of intra-cranial facial nerve • CT scan temporal bone: for progressive palsy • MRI brain • Surgical exploration

35. Topo-diagnostic tests • Audiometry:cochlear nerve function • Vestibulometry:vestibular function • Schirmer’s test:Greater Superficial Petrosal Nerve • Stapedial reflex test: Nerve to stapedius • Electrogustometry:Chorda tympani • Submandibular salivary flow: Chorda tympani • Examination for terminal facial nerve branches

37. Schirmer’s Test Unilateral wetness ed by >30% of total amount of both eyes after 5 minutes = Schirmer test positive  lesion at or proximal to geniculate ganglion

38. Stapedial Reflex

39. Electrogustometry Measures minimum amount of current required to excite sensation of taste

40. Muscles supplied by terminal branches

42. Electrical tests

43. Nerve Excitability Test • Stimulating electrode used over terminal branches of facial nerve • Minimum current intensity required to produce minimal muscle movement is calculated • Normal side compared to paralyzed side • Difference > 3.5 mAmp = unfavorable prognosis

44. Maximal stimulation test • Stimulating electrode used over terminal branches of facial nerve • Minimum current intensity required to produce maximal muscle movement is calculated • Normal side compared to paralyzed side • Difference > 3.5 mAmp = unfavorable prognosis

45. Electro-neuronography • Terminal branch of facial nervestimulated & action potential recorded in appropriate muscle • Paralyzed side compared to normal side (which is taken as 100%) • Response > 10% = 85-95 % chance of recovery • Response < 10% = 25 % chance of recovery

46. Electro-neuronography

47. Electro-neuronography

48. Electro-neuronography

49. Electromyography Records spontaneous activity of facial muscles

50. Electromyography Responses Normal Polyphasic Fibrillation Electrical Silence