FACIAL NERVE.pptx

7TH CRANIAL NERVE AND APPLIED ASPECTS

1. BIPIN KOIRALA MASTER’S OF OPTOMETRY, HEI, PU FACIAL (7 TH ) CRANIAL NERVE

2. Facial Nerve 7 th Cranial Nerve Both mixed nerve (Sensory and Motor) Originates at the level of lower Pons in brain stem

3. Functional Components There are 4 functional components: Branchial efferent for facial expressions and elevation of hyoid bone General visceral efferent component is concerned with parasympathetic supply of the lacrimal gland, submandibular and sublingual salivary glands and the nasal, palatine and pharyngeal glands

4. 3. Special visceral afferent for taste sensations (anterior 2/3 rd ) tongue 4. General somatic afferent for sensations from the concha of the auricle (Touch, Temperature and Pain) relaying at spinal nuclei of trigeminal nerve

5. Nuclei of Facial Nerve Altogether there are 3 types of Nerve Nuclei: Main Motor Nucleus: Lies deep in the reticular formation of the lower part of the pons

6. The part of the nucleus that supplies the muscles of the upper part of the face receives corticonuclear fibres from both cerebral hemispheres The part of the nucleus that supplies the muscles of lower part of the face receives corticonuclear fibres from the opposite cerebral hemisphere only

7. Parasympathetic nuclei : Situated posterolateral to the main motor nucleus Includes : Superior salvatory nuclei Lacrimator nucleus

8. 1. Superior Salivatory nucleus : Receives afferent fibres from the hypothalamus through the descending autonomic pathway Sends preganglionic fibres which will reach sub mandibular ganglion to finally innervate the submaxillary and sublingual salivary glands

9. 2. Lacrimatory nucleus: Receives afferent fibres from: Hypothalamus for emotional responses Sensory nuclei of the trigeminal nerve for reflex lacrimation secondary to irritation of the cornea or conjunctiva Sends preganglionic fibres for innervation of the lacrimal gland

10. 3. Sensory Nucleus The upper part of nucleus tractus solitarius constitutes the sensory nucleus of the facial nerve Belongs to S pecial visceral afferent nuclei

11. Situated in upper part of medulla oblongata in line with other nuclei of its group Receives afferent fibers from central processes of neurons of the geniculate ganglion of the facial nerve and also afferents from the concha of the auricle

12. The efferent fibres from the nucleus tractus solitarius ascend to thalamic nuclei From the thalamus, the axons of the thalamus end in the taste area of the cortex.

13. Course and Distribution Consists of motor and sensory root Fibres of the motor root, travel posteriorly from the medial side of the abducent nucleus and then pass around this nucleus beneath facial colliculus , finally pass anteriorly to emerge from the brain stem

14. The sensory root (nervous intermedius ) consists of central processes of the unipolar cells of geniculate ganglion. Sensory root also contains the preganglionic parasympathetic fibres from the parasympathetic nuclei

15. The two roots of the facial nerve emerge from the junction of pons and medulla just medial to 8 th cranial nerve Then the two roots run laterally and forwards (with the 8 th nerve) to reach and enter the internal acoustic meatus.

16. Here the 7 th and 8 th nerves are accompanied by the labyrinthine vessels. At the bottom of the meatus , the two roots (sensory and motor) fuse to form a single trunk, which lies in the petrous temporal bone.

17. Within the canal, in the petrous part of temporal bone, the course of the nerve can be divided in 3 parts by two bends.

18. The facial nerve leaves the skull by passing through the stylomastoid foramen Behind the neck of the mandible, it divides into its five terminal branches which emerge along the anterior border of the parotid gland.

19. In the Extra cranial Course

20. Branches Branches within the facial canal Greater petrosal nerve: Contains mainly taste fibres Relayed to the lacrimal gland Relayed to nasal and palatine mucosal glands

21. 2. Nerve to Stapedius : Supplies the stapedius muscle

22. 3. Chorda Tympani : It carries a preganglionic secretomotor fibres to the submandibular ganglion for supply of the submandibular and sublingual salivary glands Taste fibers from anterior two-thirds of the tongue (sensory)

23. B. Branches at its exit from the stylomastoid foramen: Posterior auricular nerve ( A uricularis posterior, occipitalis and intrinsic muscles on the back of the auricle) Digastric branch (P osterior belly of digastric ) Stylohoid branch ( S tylohyoid muscle)

24. 5 Terminal branches within the parotid gland : 1. Temporal branch : Frontalis Orbicularis oculi Corrugator supercilli 2. Zygomatic branch : Supplies orbicularis oculi 3. Buccal branch : Supplies to area around parotid duct

25. 4. Mandibular branch : supplies to muscles of lower lip and chin 5. Cervical branch : platysma

26. Ganglia associated with facial nerves 1. Geniculate Ganglion: Located on the first bend of the facial nerve in relation to medial wall of middle ear Sensory ganglion Taste fibres

27. 2. The submandibular ganglion : Parasympathetic ganglion Relay of secretomotor fibres from submandibular and sublingual glands

28. 3. Pterygopalatine ganglion or sphenopalatine ganglion: Largest parasympathetic peripheral ganglion. Serves as relay station for secretomotor fibres to the lacrimal gland and to mucous glands of nose, the paranasal sinuses, the palate and the pharynx. Functionally related to facial nerve even though topographically related to maxillary nerve

29. Facial palsy Etiology

30. Clinical features and assessing of patient with facial nerve palsy Motor function of the upper face is examined by having the patient raise their eyebrows to wrinkle their forehead (frontalis ) . The most important test of facial nerve function is checking eye closure (orbicularis oculi).

31. Using a cotton wisp to check the corneal reflex also evaluates efferent innervation of the orbicularis muscle through the corneal blink reflex arc. Lower facial muscle function is tested by having the patient smile and show their teeth.

32. The practitioner should evaluate any asymmetry of the patient’s smile and check for flattening of the nasolabial fold on the involved side.

33. Ocular Examination Motility evaluation Corneal sensitivity Tear film (Basal Schirmer testing) Corneal integrity

34. 5. Lower Eyelid Ectropion Patient may complain of epiphora and spilling over of tears onto cheek. This is usually result of reflex lacrimation . 6. After assessing orbicularis oculi , Bell’s phenomena should also be checked.

35. Applied aspects In supranuclear lesions of the facial nerve (usually a part of the hemiplegia), only the lower part of the contralateral face is paralyzed. Upper part (frontalis and part of orbicularis oculi) escapes due to its bilateral representation in the cerebral cortex. At this level, cerebrovascular accidents and tumors are the most likely causes.

36. In infranuclear lesions of the facial nerve, the whole of the face of the ipsilateral side is paralyzed, abolishing both voluntary and emotional movements. The face becomes asymmetrical and is drawn up to the normal side. Wrinkles disappear from the forehead

37. The eyes cannot be closed ( lagophthalmos ) Any attempt to smile draws the mouth to the normal side. During mastication, food accumulates between the teeth and the cheek

38. The common causes of infranuclear facial nerve palsy are: Bell’s palsy 2. Diseases of the brainstem 3. Acoustic neuromas

39. The lesions found distal to the chorda tympani produce isolated facial palsy. Lesions at the level of pons result in the involvement of both the abducent and facial nerve Lesions at the cerebellopontine angle result in the involvement of both the facial and auditory nerve.

40. Ramsay – Hunt syndrome It occurs due to herpes zoster infection of geniculate ganglion of facial nerve. Characterized by lower motor neuron type of facial palsy associated with severe pain in the ear and vesicles near the ear.

41. Justin B affected with Ramsay Hunt

42. Bilateral congenital syndrome in which both CN VI and CN VII palsy combine causing an esotropia and an inability to form facial expression. Aetiology : Primary developmental defects of CNS with aphasia of the motor nuclei of VI and VII nerves and denervation atrophy of facial and EOMs Mobius syndrome:

43. Bell’s palsy Mostly of etiology unknown Strong evidence implicating herpes simplex virus type 1 (HSV-1) In 85% of patients, spontaneous recovery. May be caused by autoimmune or viral induced inflammatory or ischemic injury with swelling of the peripheral nerve

44. Aberrant regeneration is common. When fibres originally designed for orbicularis oculi reinnervate lower facial muscles, each blink may cause twitch of the corner of mouth or a dimpling of the chin. Conversely, movement of lower face, such as pursing lips, smiling or chewing with the mouth closed may produce involuntary lid closure.

45. Other disorders of aberrant facial innervation include lacrimation caused by chewing (crocodile tears), in which fibers originally supplying mandibular and sublingual glands reinnervate the lacrimal gland. This syndrome usually follows severe proximal seventh nerve injury and may be accompanied by decreased reflex tearing and decreased taste from the anterior two thirds of the tongue.

46. Management In cases of orbicularis oculi involvement: Artificial tear supplements Taping the eyelid shut Moisture chamber to be used at night Avoid dusty or windy environment

47. BCL can be used in superficial punctate keratopathy Breakdown of corneal epithelium indicates need for punctal plugs, tarsorraphy , or injection of botulinum toxin to induce ptosis . Scleral contact lenses In some cases, corticosteroids are used.

48. Disorders of over activity of 7 th nerve Essential blepharospasm : Episodic contraction of orbicularis oculi Between 40-60 yrs. of age

49. Cause maybe basal ganglia dysfunction Should first exclude other causes (severely dry eyes, intraocular inflammation, and meningeal irritation) Type A botulinum toxin can be used or surgical therapy

50. 2. Hemifacial spasm: Characterized by unilateral episodic spasm that involves facial musculature Typically lasts from a few seconds to minutes Pathogenesis : compression of seventh nerve where it exits the brainstem. Starts as intermittent twitching of orbicularis oculi but over years, spreads to involve all facial muscles

51. Abnormal firing in the motor nucleus or ephaptic transmission of nerve impulses causes innervation directed toward one muscle group to excite adjacent nerve fibres directed to another muscle group Botulinum toxin A injection and facial myectomy

52. 3. Facial myokymia : Characterized by continuous unilateral fibrillary or undulating contraction of facial muscle bundles When confined to eyelid, commonly a self limited, benign condition Occasionally, these rippling movements begin within a portion of orbicularis oculi and may spread to involve most facial muscles

53. Typically signifies intramedullary disease of pons involving the seventh nerve nucleus or fascicle Usually a result of pontine glioma in children and multiple sclerosis in adults May be relieved by carbamazepine , or botulinum toxin injection

54. Summary Any clinical signs such as limited abduction, abnormal head posture, lagophthalmos, facial asymmetry, etc. are to be carefully examined to rule out possible neurological causes. Possible management should be given and be referred as needed.

55. REFRENCES AK KHURANA ANATOMY AND PHYSIOLOGY AAO section 5 Neuro -ophthalmology Thank You!