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1. DR. DIPTIMAN BALIARSINGH1st Year PG (ENT),HMCH.
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. 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. 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. Nerve Structure
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. Facial Nerve and Central connections
8. Facial nerve: Types of fibers Special Visceral
Efferent/Branchial Motor General Visceral Efferent/Parasympathetic
General Sensory Afferent/Sensory Special Visceral
Afferent/Taste
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
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. Distribution ofFACIAL NERVEfibers
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. DIVISIONS OF FACIAL NERVE Divided into 3 parts:-
Intracranial Intratemporal Extracranial
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. Intra Temporal Course: From IAC to SMF Length 28 to 30 mm
Longest bony canal 3 segments by 2 genus
18. Intra Temporal Course of Facial Nerve
19. Intra Temporal Course of Facial Nerve
20. Intratemporal Course of Facial Nerve
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. Relation of N fibres in IAC
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. 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. 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. 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. Facial recess and sinus tympani relations with facialnerve
and pyramidal eminence
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. 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. Review of the Intra Temporal part of FacialNerve, its
branches and communications
31. Facial Nerve course in relation to Middle Ear(Lateral
View)
32. Facial Nerve course in relation to Middle Ear(Medial
View)
33. Facial Nerve Course in the medial wall of middle ear
34. Nerves in relation with the middle ear
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. Course of Facial Nerve in Parotid Gland(Transverse
Section)
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. 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. 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. 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. 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. 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. Zygomatic : Also called Upper Zygomatic Cross zygomatic
bone Muscles supplied Lower Orbicularis oculi Action Tight shutting
of eye
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. 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. Cervical : Comes out through the lower pole of parotid gl.
Muscle Supplied Platysma Action Contraction of Platysma
47. Terminal branches of Facial Nerve
48. Pattern of branching of Terminal branches of Facial
Nerve(Classification & Branching pattern by Davis et al - Grays
ANATOMY)
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. 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
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. 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. 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. 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. 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. 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