Facial n


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Facial n

  1. 1. Facial Nerve Dr/ Hytham Nafady
  2. 2. Introduction Components of the facial nerve Branchiomeric motor Visceral motor (parasympathetic ) General sensory Special sensory (taste fibers)
  3. 5. Origin
  4. 6. Intracranial course <ul><li>Central segment (tegmentum pontis). </li></ul><ul><li>Cisternal segment (CPA). </li></ul><ul><li>Canalicular segment (IAC). </li></ul><ul><li>Labyrinthine segment (Fallopian canal). </li></ul><ul><li>Geniculate ganglion . </li></ul><ul><li>Tympanic segment . </li></ul><ul><li>Stylomastoid segment . </li></ul>
  5. 7. Extracranial course
  6. 8. Branches <ul><li>Intracranial: </li></ul><ul><li>Greater superficial petrosal </li></ul><ul><li>Nerve to stapedius. </li></ul><ul><li>Chorda tympani N. </li></ul><ul><li>Extracranial: </li></ul><ul><li>Posterior auricular. </li></ul><ul><li>N to posterior belly of digastric. </li></ul><ul><li>N to stylohyoid. </li></ul><ul><li>5 intraparotid terminal branches (temporal, zygomatic, buccal, mandibular & cervical). </li></ul>
  7. 9. Facial nuclei <ul><li>Motor Nuclei: </li></ul><ul><li>Facial nerve nuclei lie in reticular formation of brainstem, ventral to floor (tegmentum) of 4 th ventricle. </li></ul><ul><li>Non-Motor Nuclei: </li></ul><ul><ul><li>S alivatory </li></ul></ul><ul><ul><li>S olitary </li></ul></ul><ul><ul><li>S pinal trigeminal. </li></ul></ul>
  8. 11. 1. Central segment <ul><ul><li>Efferent fibers of facial nerve surround nuclei of CN VI & form small mounds on floor of 4 th ventricle ( facial colliculi ) </li></ul></ul>Facial colliculus
  9. 12. 2. Cisternal segment <ul><li>The cisternal cistern of the facial nerve course through the CP angle cistern . </li></ul>Facial N. AICA
  10. 13. 3. Intra-canalicular segment <ul><li>The intra-canalicular segment of the facial nerve course within the anterior superior quadrant of the internal auditory canal . </li></ul>
  11. 14. Cn 7 Post Ant
  12. 15. <ul><li>The superior and inferior divisions of the vestibular nerves are posterior and (keep you from falling back) </li></ul>
  13. 17. Fallopian Canal
  14. 19. <ul><li>Facial nerve exits IAC via Fallopian canal </li></ul><ul><ul><li>Narrowest point throughout entire course </li></ul></ul><ul><ul><li>Felt to be culprit in facial nerve compression in Bell’s palsy. </li></ul></ul>4. Labyrinthine segment Fallopian Canal
  15. 20. <ul><li>Gives rise to greater superficial petrosal nerve </li></ul><ul><ul><ul><li>Contains taste axons from tongue & somatic fibers </li></ul></ul></ul>5. Geniculate ganglion Geniculate ganglion
  16. 22. 6. Tympanic segment <ul><li>The tympanic segment course posteriorly below the lateral SCC. </li></ul><ul><li>The last parasympathetic fibers leave the nerve via the chorda tympani nerve. </li></ul>
  17. 25. <ul><li>canalicular segment. </li></ul><ul><li>Anterior genu </li></ul><ul><li>Labyrinthine segment. </li></ul>
  18. 26. 7. Stylomastoid segment Styloid process Stylomastoid foramen
  19. 31. Which parts of the facial nerve that normally enhance? <ul><li>Geniculate ganglion . </li></ul><ul><li>Tympanic segment . </li></ul><ul><li>Mastoid segment . </li></ul><ul><li>Enhancement of these segments may be asymmetrical. </li></ul><ul><li>Enhancement of these segments because of surrounding circum-neural arteriovenous plexus. </li></ul>
  20. 32. Normal enhancement of these segments is due to the presence of circumneural facial arteriovenous plexus.
  21. 33. Intraparotid segment
  22. 34. Cn 7 Cn 7 RMV RMV
  23. 38. Greater superficial petrosal N. <ul><li>The GSPN is branch of the facial nerve that innervates the lacrimal gland. </li></ul><ul><li>It contains preganglionic parasympathetic fibers. </li></ul><ul><li>It exits the superior surface of the temporal bone via the facial hiatus. </li></ul><ul><li>It passes under the Meckel’s cave to the foramen lacerum, at which it joins the deep petrosal nerve to form the vidian nerve. </li></ul><ul><li>The vidian nerve passes through the vidian canal to the pterygopalatine fossa. </li></ul>
  24. 42. Clinical Signs Suggesting Site of Facial Nerve Lesion <ul><li>Upper facial territory is supplied by bilateral motor cortices </li></ul><ul><li>Lower facial territory is supplied only by contralateral motor cortex </li></ul><ul><li>Therefore, unilateral central lesions spare upper face </li></ul><ul><li>Lesions distal to geniculate ganglion </li></ul><ul><ul><li>Mostly motor abnormalities </li></ul></ul><ul><li>Lesions proximal to geniculate ganglion </li></ul><ul><ul><li>Motor, gustatory & autonomic abnormalities </li></ul></ul>
  25. 43. Facial nerve pathology <ul><li>Idiopathic (Bell’s palsy) </li></ul><ul><li>Congenital </li></ul><ul><li>Traumatic </li></ul><ul><li>Inflammatory </li></ul><ul><li>Neoplastic </li></ul><ul><li>Vascular </li></ul>
  26. 44. Typical Bell’s Palsy <ul><li>Incidence </li></ul><ul><ul><li>Usually during winter </li></ul></ul><ul><li>Etiology not entirely understood </li></ul><ul><ul><li>Possibly viral (Herpes Simplex Virus). </li></ul></ul><ul><li>Viral infection of facial nerve results in demyelination, inflammation & swelling </li></ul><ul><ul><li>Traps nerve in narrow confines of fallopian canal </li></ul></ul><ul><li>Diagnosis of exclusion </li></ul><ul><ul><li>Made only when clinical & imaging (if necessary) findings are supportive </li></ul></ul>
  27. 45. Typical Bell’s Palsy <ul><li>Usually a clinical diagnosis </li></ul><ul><ul><li>Acute onset unilateral (lower or upper) facial paralysis, posterior auricular pain, decreased tearing, hyperacusis (30%) & disturbances of taste. </li></ul></ul><ul><li>80-90% recover completely </li></ul><ul><ul><li>Over age 60, only 40% recover completely </li></ul></ul>
  28. 46. Imaging in Typical Bell’s Palsy <ul><li>Imaging in typical Bell’s palsy is not usually necessary </li></ul><ul><ul><li>When necessary, MRI is best </li></ul></ul><ul><li>Normal facial nerve distal to geniculate ganglion may enhance </li></ul><ul><ul><li>Facial nerve proximal to geniculate ganglion does not normally enhance </li></ul></ul><ul><li>In patients with Bell’s palsy, enhancement of facial nerve in fallopian & ICA is typical </li></ul>
  29. 47. <ul><li>Canalicular </li></ul>Geniculate ganglion labyrinthine
  30. 48. Mobius syndrome <ul><li>It is a congenital disorder characterized by </li></ul><ul><li>Bilateral facial diplegia </li></ul><ul><li>Convergent squint </li></ul><ul><li>Secondary to 6 th & 7 th cranial nerve palsies </li></ul><ul><li>Associations: </li></ul><ul><li>Other cranial nerve plasies: 5 th , 9 th , 10 th & 12 th cranial nerves. </li></ul><ul><li>Craniofacial abnormalites. </li></ul><ul><li>Chest wall abnormalities. </li></ul><ul><li>Upper & lower limb abnormalities. </li></ul>
  31. 50. Mobius syndrome Normal subject
  32. 51. Temporal bone fracture <ul><li>Longitudinal </li></ul><ul><li>Incidence of facial palsy </li></ul><ul><li>20 % </li></ul><ul><li>Transverse </li></ul><ul><li>Incidence of facial palsy </li></ul><ul><li>50% </li></ul>
  33. 52. Post-traumatic facial paralysis. On the other hand, a fracture line may be seen to cross the facial nerve canal without any associated nerve dysfunction Usually there is no fracture line. A fracture line can be seen crossing the facial canal. nerve edema nerve trans-section Delayed post-traumatic facial paralysis Acute post-traumatic facial paralysis
  34. 54. <ul><li>Foville syndrome </li></ul>
  35. 55. Millard Gubler syndrome
  36. 56. Hemifacial spasm <ul><li>At rest </li></ul><ul><li>During the attack </li></ul>
  37. 57. Vertebro-basilar dolichoectasia
  38. 58. Vascular loop compression
  39. 59. Facial N. schwannoma associated with acquired arachnoid cyst
  40. 60. Intracanalicular facial shwannoma with involvement of the geniculate ganglion.
  41. 61. Geniculate ganglion schwannoma
  42. 62. Geniculate ganglion hemangioma
  43. 63. Geniculate ganglion meningioma
  44. 64. Stylomastoid segment schwannoma
  45. 65. Intra-parotid facial schwannoma <ul><li>Target sign. </li></ul><ul><li>Growth toward facial canal, which may be widened </li></ul>
  46. 68. Parotid gland adenocarcinoma with facial nerve perineural spread
  47. 69. Perineural spread along the GSPN
  48. 70. Denervation atrophy of the buccinator muscle
  49. 71. Thank you