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Facial nerve

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facial nerve

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Facial nerve

  1. 1. K.SRINIVAS Ist yr pg Department of general medicine
  2. 2. FACIAL NERVE  7th cranial nerve.  Mixed cranial nerve. motar sensory para sympathetic
  3. 3. ANATOMY Supranuclear pathway lower third of contralateral precentral gyrus Corona radiata Genu of internal capsule. Medial portion cerbralpeduncles Pons  Then decussate to converge on the facial nucleus.
  4. 4.  Lower half of the face has contralateral supranuclear control  Upper half has bilateral control.  Some of the corticobulbar fibres descend in to the aberrent pyramidal tract to the medullary levels,decussate there and ascend contralaterally in to the dorsal medulla to converge in to the facial nucleus.
  5. 5. FACIAL NUCLEUS  Special visceral efferent nerve.  Branchiomotar nerve .  Lies deep in the tegmentum of caudal pons.  3 subnuclei lateral medial dorsal
  6. 6. Sensory part  Is formed by nervus intermedius (NI) of wrisberg.  It forms 30% of the facial nerve.  Sensory and parasympathetic division of facial nerve.  Parasympathetic fibres arise from superior salivatory and lacrimal nucleus  The gustatory efferents end primarily in the nucleus of the tractus solitarius.
  7. 7. Infranuclear pathway  Facial nerve exits the pons in to the internal auditory canal at ponto medullary junction.  The nerve pierces the meninges and enter in to the facial canal at the bottom of internal auditory meatus.  3parts labyrinthine tympanic or horizantal mastoid
  8. 8. Course and branches of facial nerve  1st branch is greater superficial petrosal nerve.  2nd branch is nerve to stapedius, arises from distal tympanic or upper mastoid part.  3rd branch is nerve to chordotympani arises slightly above stylomastoid foramen.  After the exit,posterior auricular,digastric and stylohoid branches arise.  In the parotid gland,it divides in to temporofacial and cervicofacial division.
  9. 9.  Course and branches of facial nerve
  10. 10. Muscles of the face  Temporal branch innervates frontalis. corrugator . upper part of orbicularis oculi. occipitalis. procerus.  Zygomatic branch innervates lower and lateral orbicularis oculi
  11. 11.  Buccal branch innervates orbicularis oculi buccinator zygomaticus Nasalis Levator anguli oris levator labii superioris  Mandibular branch innervates mentalis risorius triangularis depressor labii inferioris lower part of orbicularis oris  Cervical branch innervates platysma
  12. 12. Clinical examination Motor system:  Inspection of the face.  Tone,atrophy and fasciculations.  Pattern of blinking  Nasolabial fold.  Palpebral fissure.  Orbicularis oculi.  Orbicularis oris.  Platysma  stapedius
  13. 13. Sensory system:  Is limited to taste  Peripheral receptors are present in the tongue epithelium,also in the soft palate and epiglottis.  5 major tastes: bitter sour sweet salty umami(delicious or savory)  Ageusia is complete inability to taste.  Hypogeusia is taste perception delayed or blunted.
  14. 14. Secretory function:  History and observation.  Schirmer test filter strips are placed in the inferior conjuctival sacs and left for 5min  Lacrimal reflex is elicited by stimulation of nasal mucosa (mechanical or chemical substances)
  15. 15. DISORDERS OF FUNCTION  Tear-hear-taste-face changes in these functions helps to localise the lesion  2 types of facial weakness. peripheral facial palsy(facial nucleus to t.branches) cental facial palsy(supranuclear pathway)
  16. 16. PERIPHERAL FACIAL PALSY  Complete paralysis.  Affected side of the face is smooth.  No wrinkles on the forehead.  Eye is open.  Inferior lid sags  Nasolabial fold is flattened  Angle of mouth droops  Epiphora
  17. 17.  Bell’phenomenon(attempting to close the involved eye causes upturning of the eyeball.  Bergara-wartenberg sign.  Platysma sign of babinski.  Corneal reflex The involved eye does not blink no matter which side is stimulated
  18. 18. BELL’S PALSY  Named after sir charless bell, scottish surgeon,anatomist,and artist.  Idiopathic facial paralysis.  Frequently after viral infections and immunization.  Nerve damage is more common in the labyrinthine part.  Most common symptoms are increased tearing,pain in and around the ear,and taste abnormalities
  19. 19. CRITERIA FOR BELL’S PALSY  There should be diffuse peripheral facial palsy.  Onset should with in a day or two.  Paralysis reaching maximum with in 3 weeks.  Full or partial recovery with in 6 months.
  20. 20. FACIAL SYNKINESIAS  It is due to aberrant regeneration.  Common after bell’s palsy and traumatic injury.  Axons destined for one muscle regrow to innervate the other.  Crocodiletears(gustatory lacrimal reflex).  Aurico temporofacial syndrome  Chordotympanic syndrome.  On blinking,corner of the mouth deviates(marin amit sign)
  21. 21. Other causes of peripheral facial paralysis  Motor neuron disease  Mobius syndrome(congenital occulofacial paralysis)  Millard-gubler syndrome  Fovile syndrome  Abscess,syringobulbia,demyelinating disease and trauma in the pons  Acoustic neuroma,meningioma in cerbello pontine angle.
  22. 22. Cont….  Ramsay hunt syndrome.  Diabetes milletus  Hiv infection  Lymes disease  Fracture of petrous bones  Melkerson syndrome is charecterised by recurrent attacks of facial palsy.  Polio myelitis
  23. 23. CENTRAL FACIAL PALSY  Weakness of lowerface with relative sparing of upper face.  Lower facial weakness is not as severe as in peripheral facial palsy.  2 variations: volitional or voluntary facial asymmetry more apparent with spontaneous expression. emotional or mimetic facial asymmetry more apparent with voluntary contraction.
  24. 24. Volitional facial palsy
  25. 25. CENTRAL FACIAL PALSY PERIPHERAL FACIAL PALSY
  26. 26. ABNORMAL FACIAL MOVEMENTS  Facial dyskinesias.  Hemifacial spasm due to intermittent compression by an ectatic arterial loop in the post circulation,most often a redundant loop of the AICA.  Spastic paretic facial contracture instead of spasm there may be fixed contracture.  Facial myokymia is acontinous,involuntary muscle quivering that has ripping worm like appearance. multiple sclerosis,Gbsyndrome,CPA tumors,SAH.
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facial nerve

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