1. 1. DR. DIPTIMAN BALIARSINGH1st Year PG (ENT),HMCH.
2. 2. Introduction : VII Cranial Nerve - Mixed N 10,000 Motor , Sensory , parasympathetic fibers Motor root 7000 special visceral efferent fibers Sensory & Parasympathetic 3000 fibers carried byNERVUS INTERMEDIUS (Nerve of Wrisberg)
3. 3. Structure of nerve : From inside out Nerve fibre consists of axon, myelinsheath, neurilemma & endoneurium A group of nerve fibre is enclosed in a sheath calledperineurium to form a fascicle The fascicles are bound together by epineurium
4. 4. Components of a Nerve : Endonerium Surrounds each nerve fiber Provides endoneural tube for regeneration Much poorer prognosis if disrupted Perinerium Surrounds a group of nerve fibers Provides tensile strength Protects nerve from infection Pressure regulation Epinerium Surrounds the entire nerve Provides nutrition to nerve
5. 5. Nerve Structure
6. 6. Facial Nerve Nuclei : Facial Nerve has 3 nuclei Motor nucleus lower pons below 4 th ventricle Superior salivatory nucleus dorsal to motor N Nucleus of tractus solitarius medulla oblongata
7. 7. Facial Nerve and Central connections
8. 8. Facial nerve: Types of fibers Special Visceral Efferent/Branchial Motor General Visceral Efferent/Parasympathetic General Sensory Afferent/Sensory Special Visceral Afferent/Taste
9. 9. Special Visceral Efferent/Branchial Motor : Premotor cortex Motor cortex Corticobulbar tract bilateral facial motor nuclei (pons) facial muscles Stapedius Stylohyoid Posterior belly of Digastric Buccinator
10. 10. General Visceral Efferent/Parasymp.: Superior salivatory nucleus (pons) nervus intermedius greater/superficial petrosal nerve facial hiatus/middle cranial fossa joins deep petrosal nerve (symp fibers 4m cerv. plexus) passes through pterygoid canal (as Vidian nerve) pterygopalatine fossa spheno/pterygopalatine gang. postganglionic parasympathetic fibers joins zygomaticotemporal nerve(V2) lacrimal gl. & seromucinous gl. of nasal & oral cavity.
11. 11. Superior salivatory nucleus nervus intermedius chorda tympani nerve joins lingual nerve submandibular ganglion postganglioic parasympathteic fibers submandibular and sublingual glands.
12. 12. General Sensory Afferent/Sensory: Sensation to auricular concha , EAC wall, part of TM,postauricular skin Cell bodies in geniculate ganglionSpecial Visceral Afferent/Taste: Postcentral gyrus nucleus solitarius tractus solitarius nervus intermedius geniculate ganglion chorda tympani joins lingual nerve anterior 2/3 tongue, softand hard palate
13. 13. Distribution ofFACIAL NERVEfibers
14. 14. Central Connections of FN Nucleus Upper part of Nucleus B/L supranuclear (cortical)innervation Lower part of Nucleus C/L supranuclear innervation Imp function of forehead preserved in supranuclearlesions
15. 15. DIVISIONS OF FACIAL NERVE Divided into 3 parts:- Intracranial Intratemporal Extracranial
16. 16. Intracranial Course: length 23-24mm Motor fibers hook around Nucleus of VI CN and joins theSensory root (N of Wrisberg) FN (+ VC N + Abdu N) leaves brainstem at Ponto-medullaryjunction F N passes through CP angle with VC N & Nervus Intermedius At the fundus of IAC, FN enters fallopian canal Devoid of epineurium - thin layer of pia mater surrounds it andcontinues into the meatal segment Surg imp : Iatrogenic trauma in CP angle tumour surgery Difficult to identify in schwannoma (no connective tissue)
17. 17. Intra Temporal Course: From IAC to SMF Length 28 to 30 mm Longest bony canal 3 segments by 2 genus
18. 18. Intra Temporal Course of Facial Nerve
19. 19. Intra Temporal Course of Facial Nerve
20. 20. Intratemporal Course of Facial Nerve
21. 21. Meatal Segment Lies in IAC Enters in ant. sup. segment of IAC Length 5 12 mm No separate sheath Shares with NI & VIII CN Baths in CSF
22. 22. Relation of N fibres in IAC
23. 23. *Bills Bar & Falciform Crescent Bill's bar was named after Dr William House It divides the superior compartment of the internal acoustic meatusinto an anterior and posterior compartment. Anterior to Bill's bar, in the anterior superior quadrant are the facialnerve (CN VII) and nervus intermedius Posterior to it in the posterior superior quadrant is the superior divisionof the vestibular nerve The falciformcrescent is a horizontal ridge that divides the internalacoustic meatus into superior and inferior portions. Superior - The facial nerve and superior vestibular nerve (SVN) travelin the superior portion of the IAM with the facial nerve anterior to theSVN and separated from it in the lateral portion by Bill's bar, a verticalridge of bone. Inferior - The cochlear nerve and inferior vestibular nerve (IVN) runinferior to the falciform crescent with the cochlear nerve situated moreanteriorly.
24. 24. Labyrinthine Segment Narrowest(0.68mm) & Shortest(3-5mm) From Meatal foramen to Geniculate Ganglion (1st Genu) No anastomosing arteries Periostium is thicker Relations :- the segment is Posterocephald (Posterosuperior) to cochlea Anteromedial to Sup SCC Cephald (Superior) to vestibule Continuation of Internal auditory canal
25. 25. Surgical importance: Anatomical bottle neck ischemia in oedema resulting inBELLS PALSY, Part most vulnerable for ischemia (no arterialanastomosis & surrounded by dense arachniod band) Temporal bone # - MC injured Geniculate ganglion :(distal end) Bipolar ganglion cells - Afferent input pain & taste fibres Secretomotor fiber to lacrimal gland by GSPN
26. 26. Tympanic Segment From Geniculate ganglion to 2nd genu Length 8 to 11 mm Lies beneath LSCC & above OW At its proximal end above & medial to Processuscochleariformis & TT muscle. Creates 2 recesses Facial recess (lat) Sinus tympani(med)
27. 27. Facial recess and sinus tympani relations with facialnerve and pyramidal eminence
28. 28. Surgical importance: Processus cochleariformis (consistant landmark) Imp landmark for 2 nd genu Hug the inf. LSCC Pyramidal eminence B/w short process of incus(L) & Lat SCC(M)
29. 29. Mastoid Segment From 2 nd genu (PM) to SMF(AL) Longest (13mm) Landmark Digastric Ridge identified by medialaspect of mastoid tip FN leaves FC via SMF (b/w mastoid tip & styloidprocess) Has 3 brances Chorda Tympani N to stapedius sensory auricular branch
30. 30. Review of the Intra Temporal part of FacialNerve, its branches and communications
31. 31. Facial Nerve course in relation to Middle Ear(Lateral View)
32. 32. Facial Nerve course in relation to Middle Ear(Medial View)
33. 33. Facial Nerve Course in the medial wall of middle ear
34. 34. Nerves in relation with the middle ear
35. 35. Extra Cranial Course From SMF to Terminal branches Runs in substance of parotid Main trunk divides forming Pes anserinus upper temperofacial lower cervicofacial Superficial to Retromandibular vein & Ext. carotid art
36. 36. Course of Facial Nerve in Parotid Gland(Transverse Section)
37. 37. Branches of Facial N: Intra temporal region : GSPN N to Stapedius Chorda Tympani Sensory Auricular branch Extra temporal region Posterior Auricular Nerve Muscular branches Stylohyoid Post. belly of Diagastric Terminal Branches Temporal Zygomatic Buccal Marginal Mandibular Cervical
38. 38. Intra temporal region: GSPN: From Geniculate ganglion 2 types of fibers arise Preganglionic parasympathetic Pterygopalatine gang. Postganglionic lacrimal gland Sensory fibers to nasal & palatine glands joins Deep Petrosal N N of pterygoid canal Nerve to Stapedius: 6mm above SMF Supply - Stapedius
39. 39. Sensory Auricular Br: Joins auricular br of vagus Supply retro-auricular groove & concha Chorda tympani Br: 4-5mm above SMF Lat & ant to Facial N Passes b/w long process incus & upper part of handle ofmalleus 2 types of fibers Preganglionic parasympathetic Submandibular Ganglion Postganglionic submandibular & sublingual gland Special sensory ant 2/3 rd of tongue
40. 40. Surgical importance: GSPN - landmark in middle cranial fossa approach CT landmark in posterior tympanotomy CT lateral margin of facial recess CT medial limit for facial ridge in CWD
41. 41. Extratemporal region: The stylomastoid foramen medial aspect of mastoid tip FN exit from Stylomastoid Foramen below tympanic plate & Lat to the base of styloid nonvascular area Lateral to base of carotid sheath &behind the parotid gland Post. Auricular N Muscles of pinna Occipitofrontalis Muscular Branches Post. belly of digastric Stylohyoid
42. 42. Terminal branches : Temporal : Comes out through the upper pole of parotid gland Cross zygomatic arch Muscles supplied Auricularis anterior & superior Frontalis Corrugator supercilii Procerus Upper orbicularis oculi Action Raising eyebrows
43. 43. Zygomatic : Also called Upper Zygomatic Cross zygomatic bone Muscles supplied Lower Orbicularis oculi Action Tight shutting of eye
44. 44. Buccal : 1 cm below zygomatic arch 2 in number -Upper deep buccal & Lower deep buccal runs along parotid duct Muscles supplied :- Risorius (smirk) Buccinator (aids chewing) Levator Labii Superioris Alaque Nasi (snarl) Levator Anguli Oris (soft smile) Nasalis (Flare Nostrils) Upper Orbicularis Oris Action Showing Teeth
45. 45. Marginal Mandibular(RamusMandibularis) : Comes out through the ant. border of parotid gland Runs 1-2cm below the ramus of mandible inferiorly Supplies muscles of lower lip & chin Lower Orbicularis Oris Deperessor anguli oris Depressor labii inferioris Mentalis Actions Whistle & Puckering of Lips
46. 46. Cervical : Comes out through the lower pole of parotid gl. Muscle Supplied Platysma Action Contraction of Platysma
47. 47. Terminal branches of Facial Nerve
48. 48. Pattern of branching of Terminal branches of Facial Nerve(Classification & Branching pattern by Davis et al - Grays ANATOMY)
49. 49. Katz & Catalano classification: Type I (25%)no anastomic links bet the 2 branches Type II (14%) buccal branch subdivided Type III(44%) Type IV(14%) Type V(3%)
50. 50. Anatomical Relationship of FN in Adults & Children:Child Absent mastoidprocess & incompletetympanic ring. CTmay exit thru SMF 2nd genu is moreacute & lateral N trunk on exit fromSMF is more anterior& lateral N very superficialover angle ofmandibleAdult Mastoid process &complete ring . CTexits separately proxto SMF 2nd genu less acute& more medial Parotid is more post.N trunk is lessanterior & deeper N superficial overangle of mandible
51. 51. Blood Supply : Ant. Inf. Cerebellar Art. Supply nerve in CP angle Intracranial/Meatal Labyrinthine branches fromAICA Geniculate & Peri-geniculate Superficial Petrosalbranch of Middle Meningeal Artery Tympanic/Mastoid Stylomastoid branch ofPosterior Auricular Artery
52. 52. Facial Nerve embryonic development: Facial nerve course, branching pattern, andanatomical relationships are established during thefirst 3 months of prenatal life The nerve is not fully developed until about 4 years ofage The first identifiable FN tissue is seen at the 3rd weekof gestation- facioacoustic primordium or crest
53. 53. Facial nerve embryology - 4th week By the end of the 4 th week, the facial and acousticportions are more distinct The facial portion extends to placode The acoustic portion terminates on otocyst Facial nerve embryology - 7th week Early 7 th week, geniculate ganglion is well-defined andfacial nerve roots are recognizable The nervus intermedius arises from the ganglion andpasses to brainstem. Motor root fibers pass mainly caudal to ganglion
54. 54. Facial nerve embryonic development: Extratemporal segment FN branches: Proximal branches form - First 6th week, Posterior auricular branch > branch of digastric - Early 8th week, Temporofacial and Cervicofacial divisions - Late 8 th week (5 majorperipheral subdivisions present) Extratemporal segment other nerves : Facial nerve communicates with peripheral branches of CN V, IX, X, cervical cutaneous nerves greater auricular nerve transverse cervical branches of the cervical plexus (C2, C3) Trigeminal nerve: auriculotemporal , infraorbital , buccal , mentalbranches All connections are complete by week 12, except for connections tobranches of CN V at orbit periphery - these are completed at 4.5months
55. 55. Surgical Landmarks : Ear & Mastoid surgery Geniculate ganglion lies behind & superior to Processuscochleariformis 2nd genu hugs inferior aspect of LSCC Facial N lies above OW niche Incus lies lateral to Facial N Facial N runs behind Pyramid Facial N lies 6-8mm inferior to Tympano-mastoid suture Digastric ridge mastoid segment Parotid surgery Tragal pointer Fn lies 1cm deep to it FN lies 1cm inferior to Tympanomastoid suture N bisects angle b/w Post belly of digastric & ear canal Buccal br 1 cm below & parallel to zygomatic arch N lies lateral to Styloid process & Superficial to Retromandibular vein
56. 56. Variations: MC variations Facial N displacements Dehiscence of fallopian canal 50% -MC Dehiscence in tympanic/horizontal seg (91%) Vertical seg. variations Bifurcation/ Trifurcation of the N Ant displaced N With post hump
57. 57. THANK YOU REFERENCES:- GRAYs Anatomy - 29th Edition Scott Browns Otorhinolaryngology & Head and Neck Surgery 7th Edition Cummings Otolaryngology & Head and Neck Surgery -5th Edition Glasscock-Shambaugh Surg. of EAR 6th Edition Mohan Bansal 2nd Edition BD Chaurasias Human Anatomy 3rd Edition