Facial nerve anatomy/certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.


Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
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Facial nerve anatomy/certified fixed orthodontic courses by Indian dental academy

  1. 1. Facial Nerve Embryology, Anatomy, Evaluation INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. Case presentation  HPI: 20 yo M s/p fall from bike without helmet, + LOC, +EtOH  PMH/PSH/Med/All/Fam hx/Soc hx: neg  PEX: AVSS, A&O x3, PERRLA Ears: R hemotympanum,BC>AC L TM WNL, AC>BC, Weber R Nose/OC/OP/Neck: WNL Face: Abrasions to R forehead, L lip CN II-XII intact  CT head: WNL  Other injuries: R clavicle and scapula fx www.indiandentalacademy.com
  3. 3. Case presentation  Returns to ER 5 days from trauma with acute onset of R facial paralysis and with R decreased hearing  HB VI, R hemotympanum, R Weber, R BC>AC  CT temporal bone: Longitudinal R temporal bone fracture, sparing otic capsule  2 week steroid taper, f/u clinic 5 days www.indiandentalacademy.com
  4. 4. Facial nerve embryonic development  Facial nerve course, branching pattern, and anatomical relationships are established during the first 3 months of prenatal life  The nerve is not fully developed until about 4 years of age  The first identifiable FN tissue is seen at the third week of gestation-facioacoustic primordium or crest www.indiandentalacademy.com
  5. 5. Facial nerve embryology: 4th week  By the end of the 4th week, the facial and acoustic portions are more distinct  The facial portion extends to placode  The acoustic portion terminates on otocyst www.indiandentalacademy.com
  6. 6. Facial nerve embryology: 5th week  Early 5th week, the geniculate ganglion forms  Distal part of primordium separates into 2 branches: main trunk of facial nerve and chorda tympani www.indiandentalacademy.com
  7. 7. Facial nerve embryology: 5th week  Near the end of the 5th week, the facial motor nucleus is recognizable  The motor nuclei of CN VI and VII initially lie in close proximity. The internal genu forms as metencephalon elongates and CN VI nucleus ascends www.indiandentalacademy.com
  8. 8. Facial nerve embryology: 7th week  Early 7th week, geniculate ganglion is well- defined and facial nerve roots are recognizable  The nervus intermedius arises from the ganglion and passes to brainstem. Motor root fibers pass mainly caudal to ganglion  Can patients with congenital facial paralysis have intact taste? Why? www.indiandentalacademy.com
  9. 9. Facial nerve embryology: 7th week www.indiandentalacademy.com
  10. 10. Facial nerve embryonic development: Intratemporal course and branches www.indiandentalacademy.com
  11. 11. Facial nerve embryonic development: Extratemporal segment - branches  Proximal branches form first  6th week, posterior auricular branch>branch of digastric  Early 8th week,temporofacial and cervicofacial divisions  Late 8th week, 5 major peripheral subdivisions present www.indiandentalacademy.com
  12. 12. Facial nerve embryonic development: Extratemporal segment – other nerves  Facial nerve communicates with peripheral branches of CN V, IX, X, cervical cutaneous nerves  greater auricular nerve and transverse cervical branches of the cervical plexus (C2, C3)  Trigeminal nerve: auriculotemporal, infraorbital, buccal, mental branches  All connections are complete by week 12 except for 4 (connections to branches of CN V at orbit periphery)-these are complete at 4.5 months www.indiandentalacademy.com
  13. 13. Peripheral communications of facial nerve www.indiandentalacademy.com
  14. 14. Facial nerve embryonic development: Extratemporal segment – Parotid www.indiandentalacademy.com
  15. 15. Anatomic segments of facial nerve  Intracranial: brainstem to IAC  Meatal: fundus of IAC to meatal foramen (narrowest aperture of FN’s bony canaliculus  Labyrinthine: meatal foramen to geniculate ganglion (first genu)  Tympanic/horizontal: ganglion  adj to oval window  pyramidal eminence of stapedius tendon  Mastoid/vertical: second genu to SM foramen  Extratemporal: SM foramen to facial muscles www.indiandentalacademy.com
  16. 16. 3-D t bone www.indiandentalacademy.com
  17. 17. Facial nerve: types of fibers  Special Visceral Efferent/Branchial Motor  General Visceral Efferent/Parasympathetic  General Sensory Afferent/Sensory  Special Visceral Afferent/Taste www.indiandentalacademy.com
  18. 18. Special Visceral Efferent/Branchial Motor  Premotor cortex  motor cortex  corticobulbar tract  bilateral facial motor nuclei (pons)  facial muscles  Stapedius, stylohyoid, posterior digastric, buccinator www.indiandentalacademy.com
  19. 19. General Visceral Efferent/Parasympathetic  Superior salivatory nucleus (pons)  nervus intermedius  greater/superficial petrosal nerve  facial hiatus/middle cranial fossa  joins deep petrosal nerve (symp fibers from cervical plexus)  thru pterygoid canal (as vidian nerve)  pterygopalatine fossa  spheno/pterygopalatine ganglion  postganglionic parasympathetic fibers  joins zygomaticotemporal nerve(V2)  lacrimal gland & seromucinous glands of nasal and oral cavity  Superior salivatory nucleus  nervus intermedius  chorda  joins lingual nerve  submandibular ganglion – postganglioic parasympathteic fibers  submandibular and sublingual glands www.indiandentalacademy.com
  20. 20. General Sensory Afferent/Sensory Sensation to auricular concha, EAC wall, part of TM, postauricular skin Cell bodies in geniculate ganglion www.indiandentalacademy.com
  21. 21. Special Visceral Afferent/Taste  Postcentral gyrus  nucleus solitarius –> tractus solitarius – nervus intermedius  geniculate ganglion – chorda tympani  joins lingual nerve  anterior 2/3 tongue, soft and hard palate www.indiandentalacademy.com
  22. 22. __________ www.indiandentalacademy.com
  23. 23. Facial nerve blood supply  Intracranial/Meatal: labyrinthine branches from ant inf cerebellar artery  Perigeniculate: superficial petrosal branch of middle meningeal artery  Tympanic/Mastoid: stylomastoid branch of posterior auricular artery www.indiandentalacademy.com
  24. 24. www.indiandentalacademy.com
  25. 25. Nerve fiber components  Epineurium – nerve sheath; vasa nervorum  Perineurium – surrounds endoneural tubules; tensile strength, protects against infection  Endoneurium – surrounds axons, adherent to Schwann layer, endoneural tubules regeneration www.indiandentalacademy.com
  26. 26. Pathophysiology of nerve injury: Sedon classification  Neuropraxia – conduction blockade from body to distal; distal nerve can still be stimulated. External compress vs intraneural edema  Axonotmesis – wallerian degeneration distal to lesion with preservation of endoneural tubules  Neurotmesis – wallerian degeneration and loss of endoneural tubules/regen layer www.indiandentalacademy.com
  27. 27. www.indiandentalacademy.com
  28. 28. Nerve injury www.indiandentalacademy.com
  29. 29. Causes of facial paralysisCauses of facial paralysis www.indiandentalacademy.com
  30. 30. www.indiandentalacademy.com
  31. 31.  h/o recurrent alternating facial paralysis  Recurrent orofacial edema (lasts<48 hrs)  chelitis  Fissured tongue  What do I have? www.indiandentalacademy.com
  32. 32. HB Facial Nerve Grading www.indiandentalacademy.com
  33. 33. www.indiandentalacademy.com
  34. 34. Topognostic testing  Mainly of historical interest; not prognostic  Uses branching pattern of the facial nerve to identify site of lesion, but is not reliable  Tearing – Schirmer’s test  Stapes reflex – Change in acoustic impedence caused by superthreshold stimulus; stapedial branch of FN is the first efferent branch www.indiandentalacademy.com
  35. 35. Auditory testing  To eval for concurrent SNHL or CHL  CHL – middle ear tumors, cholesteatomas, other processes involving tympanic segment  SNHL – acoustic neuromas, meningiomas, congenital cholesteatoma, others involving CPA or IAC www.indiandentalacademy.com
  36. 36. Electrophysiologic tests  Measures nerve conduction; from proximal to injury site to muscle/evoked electrical signal.  Cannot measure proximal to stylomastoid foramen  Require waiting until degeneration has progressed enough to be detectable. www.indiandentalacademy.com
  37. 37. Nerve stimulation test  NST -office-based, stim main branches with 1 millisec wave pulse, minimal thresholds for facial muslce response are compared  3.5 milliampere difference is pathologic; not sens to lesser degrees of nerve transmission that do not result in loss of visible face motion  Why can’t this test be used during the first 72 hours after injury? www.indiandentalacademy.com
  38. 38. Maximal stimulation testing  Variation of NST, but uses maximal stimulation at a level sufficient to depolarize all motor axons under the stimulator  Stim 5 peripheral branches and main trunk  Compares both sides; subj grading  Bell’s – Equal B results up to 10 days, 92% with full recovery. Response lost within 10 days, 100% had incomplete return (May, et al) www.indiandentalacademy.com
  39. 39. Electroneuonography ENog/ Evoked electromyography EEMG  Similar to MST except the measured end point is evoked muscle compound action potential amplitudes and latencies (not visible muscle movement); used after 2 weeks of injury  Recording electrodes on nasal alae, stimulator under zygomatic arch www.indiandentalacademy.com
  40. 40. EEMG  The peak-to-peak amplitude is proportional to the number of intact motor axons  Example: 10% of normal amplitude = 90% degeneration www.indiandentalacademy.com
  41. 41. EEMG - tumor www.indiandentalacademy.com
  42. 42. EEMG – Bell’s  Progressive degeneration – 3,4,5 days post-onset  MA = masseter artifact, can be confused with small evoked potential, ID by very short latency www.indiandentalacademy.com
  43. 43. Electromyography  Measures activity of muscle (from volitional contraction) instead of the nerve  Measured at insertion, voluntary contraction, at rest  Helps to eliminate false positive NET/MST/EEMG  Diagnostic, not prognostic www.indiandentalacademy.com
  44. 44. EMG – insertional, at rest  A – normal needle insertional activity (dec w/ muscular fibrofatty changes)  B – Positive sharp waves (denervation)  C – *Fibrillations (denervation 10-20d)  D – Bizarre formations (myopathies, neuropathies) www.indiandentalacademy.com
  45. 45. Motor unit action potential  The motor unit tested by EMG is only a small portion of the muscle fibers in an anatomic motor unit  Motor unit action potential/MUAP is the sum of early discharges of some muscle fibers of one motor unit  Nl MUAP: bi/triphasic, amp 0.3-0.5mv, duration 3- 16ms www.indiandentalacademy.com
  46. 46. EMG  A, inserting needle activity. For suspected muscle atrophy- reanimation usu doesn’t work 2 not enough muscle present.  B. Fibrillation potentials can be seen in conduction block and complete disruption  C. Contracting muscle/smile. Polyphasic potentials indicative of early nerve regenration; polyphasic patterns can be seen in myopathies  D. Recruitment/interference assessed my maximal contraction of a muscle group www.indiandentalacademy.com
  47. 47. Limitations of electrophysiologic testing  72 hours delay for MST and EEMG  EMG delay ~14 days until fibrillations seen  Normal variations can be great. EEMG response of 50% have been seen in normal controls.  Must correlate clinical findings with results  Future? Magnetic nerve stimulation for intracranial stim/stim prox to lesion www.indiandentalacademy.com
  48. 48. www.indiandentalacademy.com
  49. 49. References  May – The Facial Nerve  Burgess – Reanimation of the Paralyzed Face  Rubin – The Paralyzed face  Netter – Collection of Medical Illustrations, Vol I:Nervous System  May M, Blumenthal FS, Klein SR: Acute Bell’s palsy: prognostic value of evoked electromyography, maximal stimulation, and other electrical tests. Am J Otol 5: 1, 1983.  Darrouzet, et al. Management of facial paralysis resulting from temporal bone fractures: Our experience ein 115 cases. Otol-Head Neck Surg 125:77-84, 2001.  Jenny AB et al. Organization of the facial nucleus and corticofacial projection in the monkey: a reconsideration of the upper motor neuron palsy. Neurology 37:930-939, 1987. www.indiandentalacademy.com
  50. 50. www.indiandentalacademy.com Thank you For more details please visit www.indiandentalacademy.com

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