2. It is a mixed nerve having both motor and sensory roots motor root supplies the muscles of facial expression Sensory root has afferent fibres conveying taste sensation from anterior 2/3rds of tongue and efferent which are parasympathetic and secretomotor FACIAL NERVE

4. The course of the nerve divided into 1.Intra cranial 2.Intratempora 3.Extratemporal Intracranial : Motor nucleus situated in the floor of the fourth ventricle where it winds round the 6th nerve nucleus producing facial colliculus

5. Taste sensation is conveyed to the tractus solitarious secretomotor fibres arise from the superior salivary nucleus Upper part of the motor nucleus which innervates fore head muscles receives fibres from both sides of cerebral hemispheres Lower part of the nucleus which supplies lower face gets only crossed fibres from one hemisphere SENSORY NUCLEUS

6. The function of fore head muscles is preserved in supra nuclear lesions because of bilateral innervation Facial nucleus also receives fibres from thalamus by alternate routes and provides involuntary control to facial muscles

7. The emotional movements as smiling and crying are thus preserved in supranuclear lesions

8. The two roots of the facial nerve emerge from the lower border of the pons and enter the internal auditory meatus along the 8 th nerve Intratemporal part : 1.Meatal segment : within internal acoustic meatus 2.labyrinthine segment : Two roots fuse together at the fundus of the I.A.M and pass laterally over the labyrinth

9. Then the nerve reach the medial wall of the middle ear just behind the processus cochleariformis The nerve forms the anterior genu here and is wider known as Geniculate ganglion In labyrinthine segment the canal is narrow and is prone to early compression in bells palsy

10. Tympanic segment : From the geniculate ganglion it passes just above the oval window and below the lateral semicircular canal Mastoid segment : From the pyramid to stylomastoid foramen

11. Extra cranial part : From the stylomastoid foramen to its peripheral branches Branches of facial nerve : Greater superficial petrosal nerve It arises from the geniculate ganglion carries secretomotor fibres to lacrimal gland and nasal mucosa

12. Nerve to stepedius : It arises at the level of second genu supplies stepedius muscle Cordatympani:it arises from the middle of the vertical segment passes between malleus and incus leaves the tympanic cavity through petrotympanic fissure

13. It carries secretomotar fibres to submandibular and sublingual glands Taste from the anteroir 2/3rds of the tongue

14. Communicating branch : It joins the auricular branch of vagus It supplies the concha,retroauricular groove, posterior meatus and outer surface of the tympanic membrane Posterior auricular nerve : It supplies muscles of pinna occipital belly of occipitofrontalis Communicates with auricular branch of vagus

15. Muscular branches to : Stylohyoid Posterior belly of diagastric Occipital belly of occipitofrontalis Poterior auricular muscles Terminal branches to muscles of facial expression Temporal.Zygomatic.Buccal mandibular. Cirvical

16. SURGICAL LAND MARKS OF FACIAL NERVE Processus cochleariformis Oval window and horizontal secircular canal Short process of incus Pyramid Tympanomastoid suture Diagastric ridge

17. SEVERITY OF THE NERVE INJURY Neuropraxia : Physiological block with no anatomical disruption It lasts only few days full return of function is expected

18. Aaxonotomesis : Axon sheath is intact but the axon is devided. Degeneration of the nerve fibres occur sheath remains intact, most of the fibres tend to regenerate, mismatching may occur leading to synkinesis

19. Neuronotmesis : Whole nerve is severed degeneration of the distal segment occur neuroma may form at the lesion from excessive fibrosis and scaring the end result of this condition is poor

20. Based on anatomical structure of the nerve : Class 1 : Only axon itself is effected as in a physiological block Class 2 : Division in the individual axon but not in the surrounding perineurium

21. Class 3 : The axon and perineurium are devided but not endoneurium Class 4 : The axon and perineurium and endoneurium are all divided but not the nerve sheath itself Class 5 : It is synonymous with neuronotmesis

22. CAUSES OF FACIAL PARALYSIS

23. The commonest cause of facial palsy This is a lower motor neuron lesion of unknown cause Both sexes are equally effected Positive family history is present in 6-8% of patients Risk of bells palsy is more in diabetics (angiopathy) and pregnant women (retention of fluid ) BELL’S PALSY

24. Viral infection : Herpes simplex,herpes zoster or E. B virus Other cranial nerves may also be involved in bells palsy which is thus considered a part of the total picture of polyneuropathy AETIOLOGY

25. Vascular ischaemia : It may be primary or secondary Primary ischeamia induced by cold or emotional stress Secondary ischeamia is the result of primary which causes increased cappillary permiability leading to exudation of fluid, oedema and compression of microcirculation of the nerve

26. Hereditary : The fallopian canal is narrow because of hereditary predisposition and this makes the nerve susceptible to early compression with slightest oedema 10% have the positive family history

27. Autoimmune disorder : T-lymphocyte changes have been observed Clinical features : On set is sudden patient unable to close the eye On attempting to close the eye the eye ball turns up and out (bells phenomenon)

28. Due to the loss of blinking epiphora is present Deviation of angle mouth to opposite side Drooping of the corner of the mouth Loss of taste Pain arround the ear may be present T.M normal Hearing tests normal

29. Typical bells palsy has certain characters : It is acute onset unilateral Numbness or pain present in face neck or tongue in majority of cases Loss or decreased ipsilateral stapedial reflex in majority of cases Red or congested chorda tympani present

30. Lesions at c.p angle : Associated with paralysis of other nerves like 8th, 5th, 6th nerves Lesions at internal auditory canal : Associated with 8th nerve paralysis Slow and complete loss of facial nerve function occurs SITES OF LESIONS

31. Lesions at geniculate ganglion : Dry eye, dry mouth diminished taste sensation. Greater superficial petrosal nerve is involved

32. Tympanomastiod segment lesions : Loss of stapedial reflexand chorda tympani nerve function Lesion at the parotid gland : Individual branches are involved No hearing defect Salivary flow Taste are normal

33. In bells palsy exact site of lesion not known Now a days it is thought that petrous part lateral to the internal auditory canal is the narrowest part and is the common site of lesion Some people feel it is due to viral infection in the brain stem

34. Histopathology : Hypereamia of nerve sheath oedema of the nerve Wallerian degeneration with vascular engorgement

35. Topographic tests : Shirmer’s tests : Lacrimation is absent if greater superficial petrosal nerve is involved Tests for taste sensation electrogustometry for testing taste sensatoin over the tongue FACIAL NERVE FUNCTION TESTS

36. Normal response is metallic taste, shock is felt if paralysed Lesions of chordatympani causes altered taste sensation Salivary flow tests : By cannulating whartons duct Stapedial reflex lost due to involvement of nerve to stapedius

37. Electrodiagnostic tests : Minimal N. E.T : Nerve isstimulated at steadily increasing intensity till facial twich is just noticeable This is compared with normal side no difference bet normal and paralysed side in conduction block

38. Nerve excitability is lost in injuries where degeneration sets in when the difference bet two sides exceeds 3.5mm the test is positive for degeneration. it takes 48 to72hrs after injury M.S.T : Maximum facial movement is determined and compared with normal side

39. Electroneurography : It gives information about the proportion of fibres in the nerve that have degenerated Surgical decompression is indicated when summation potential falls to 10% of the normal value

40. Electromyography : It records spontaneous activity of facial muscles by direct insertion of electrodes into the muscles denervated muscle shows fibrillation potentials but they appear only 14 to 21 days after denervation has started It is useful to show earliest signs of recovery

41. General : Reassurance care of the eye to prevent exposure keratitis Relief of pain by analgesics physiotherapy to facial muscles TREATMENT

42. Medical management : Steroids : Prednisalone1mgper kgbody wt bd for 5days If the pt is recovering, dose is tapered during the next 5 days If the paralysis remains complete the same dose is continued for another10days, tapered in next 5days

43. Steroids also useful to prevent synkinesis,crocodile tears and to shorten the recovery time of facial paralysis Steroids can be combined with acyclovir Vasodilaters vitamines mast cell inhibitors antihistamines are also useful

44. Surgical treatment : Nerve decompression relieves pressures on the nerve and improves microcirculation of the nerve prognosis is good in incomplete palsy and in those where clinical recovery starts within 3 weeks of onset

45. MELKERSSON’S SYNDROME Consists of triad of facial paralysis Swelling of lips and fissured tongue paralysis may be recurrent Rx is same as in bells palsy

46. Recurrent facial palsy seen in bells palsy Melkerssons syndrome diabetes sarcodosis and tumours recurrent palsy on the same side may be caused by tumour in30%of cases

47. Incomplete recovery : Eye cannot be closed resulting in epiphora Weak oral sphincter causes drooling of saliva and difficulty in taking food COMPLICATIONS OF FACIAL PALSY

48. Exposure keratitis : Tear film from the cornea evaporates causing dryness, exposure keratitis corneal ulcer it can be prevented by artificial tears (methylcellulose drops) every 1 – 2 hrs Eye ointment proper cover for the eye at night Ttemporary tarsoraphy may also be indicated

49. Synkinesis : When the patient wishes to close the eye corner of the mouth also twiches It is due to cross innervation of fibres no treatement for this condition Tics and spasms : Result of regeneration of fibres, invountary movements seen on the effected side

50. Contractures : They result from fibrosis of atrophied muscles they effect Movement of the face But facial symmetry at rest is good

51. Crocodile tears (gustatory lacrimation ) : Unilateral lacrimation with mastication This due to faulty regeneration of parasympathetic fibres which now Supply lacrimal gland instead of salivary glands It can be treated by section of greater superficial petrosal nerve or tympanic neurenectomy

52. Freys syndrome : There is sweating and flushing of skin over the parotid during mastigation It result from parotid surgery

53. Surgery of facial nerve : Decompression : The bony canal is exposed and uncapped the sheath of the nerve is also slit to relieve pressure due to oedema or intraneural heamatoma End to end anastomosis : If the gap is few mm in extratemporal part there should not be any tention in the approximated ends

54. Nerve graft : Great auricular,lateral cutaneous nerve of thigh or sural nerve Hypoglossal-facial anastomosis : Plastic procedures : Facial slings, face lift operations Slings of masseter and temporalis muscles