facial nerve


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  Notes
 
 
1 : FACIAL NERVE PRESENTER: DONA BHATTACHARYA (PG 1st YEAR)
2 : CONTENTS Introduction Embryology Nucleus of origin Course Branches of facial nerve Functional components Ganglia associated with facial nerve Blood supply
3 : Variations of nerve Testing of facial nerve Identification of facial nerve Complications of facial dissection Facial nerve lesions Congenital anomalies Conclusion References
4 : Introduction -VII cranial nerve Mixed nerve 2 roots: a) motor root b) sensory root
5 : INTRACRANIAL EMBRYOLOGY OF THE FACIAL NERVE
6 : Facial nucleus – neuroblasts in PONS with 6th Nerve nucleus in close proximity As brain develops – pons expands – “INTERNAL GENU” Surg imp : any inflammatory event in this part – both Nerve involved
7 : NUCLEUS OF ORIGIN Motor nucleus Superior salivary nucleus Special lacrimatory nucleus Nucleus of tractus solitarius
8 : Motor nucleus
9 : Superior salivary nucleus
10 : Special lacrimatory nucleus
11 : Nucleus of tractus solitarius
12 : COURSE Interaneural – motor route joins the fibers from superior salivary nucleus and loops with 6th nerve nucleus (facial colliculus)
13 : Extraneural course – Intrapetrous part of facial nerve – Internal acoustic meatus Tympanic cavity - forms geniculate ganglion comes out through stylomastoid
14 : Extra cranial part – Termination –
15 : Branches Branches of communication Branches of distribution
16 : BRANCHES OF COMMUNICATION
17 :
18 : Branches of distribution Facial canal Nerve to stapedius Chorda tympani In face Temporal Zygomatic Buccal Marginal mandibular Cervical Stylomastoid foramen Posterior auricular Nerve to stylohyoid Nerve to digastric (posterior belly)
19 : Intra temporal region : GSPN N to stapedius Chorda tympani Sensory auricular branch
20 : GREATER PETROSAL NERVE Functional components Parasympathetic preganglionic secretomotor fibers Special taste sensation
21 : Nerve to stapedius 6mm above Stylomastoid foramen Supply stapedius
22 : CHORDA TYMPANI NERVE Functional components Parasympathetic preganglionic secretomotor fibers Special taste sensation
23 : Surgical importance: Greater Superior Petrosal Nerve - landmark in middle cranial fossa approach Chorda Tympani – landmark in middle ear surgical procedures
24 : POSTERIOR AURICULAR NERVE Arises below stylomastoid Supplies Auricularis posterior Occipitalis Intrinsic muscles on back of auricle
25 : Terminal branches
26 : ZYGOMATIC TEMPORAL Temporal : Cross zygomatic arch Auricularis anterior & superior;frontalis; orbicularis oculi & corrugator supercilii Zygomatic : Cross zygomatic bone Orbicularis oculi
27 : Marginal mandibular : 1-2cm below inf ramus of mandible Muscles of lower lip & chin Cervical : Platysma &depressor anguli oris Buccal : 1 cm below zyg arch Along parotid duct BUCCAL MANDIBULAR CERVICAL
28 : Buccal branch supplies : Risorius (smirk) Buccinator (aids chewing) Levator Labii Superioris Levator Labii Alaque Nasi (snarl) Levator Angulis Oris (soft smile) Nasalis (Flare Nostrils) Orbicularis Oris (Purse Lips)
29 : BLOOD SUPPLY
30 : Functional components Somatic Efferent Facial muscles Platysma Stylohyoid Digastric Visceral Efferent Secretomotor fibers Special Visceral Efferent Taste sensations Somatic Afferent Proprioceptive impulses
31 :
32 : GANGLIA ASSOCIATED WITH THE FACIAL NERVE Geniculate ganglion Submandibular ganglion Pterygopalatine ganglion
33 : GENICULATE GANGLION
34 : SUBMANDIBULAR GANGLION
35 : PTERYGOPALATINE GANGLION
36 : VARIATIONS OF FACIAL NERVES Buccal branch usually single, two branches in 15% cases Marginal mandibular branch – pass bellow the lower border of mandibal, incident varying between 20-50% Cervical branch – 20% cases, two branches 4. Katz and Catalano (14) reported three cases (3%) presenting two main trunks, known as the major and minor trunks of facial nerve. 5. Baker and Conley (17) reported trifurcation, quadrifurcation, or even a plexiform branching pattern of the trunk of the facial nerve
:
38 : Modified davis et al classification Source: The surgical anatomy of the facial nerve with special reference to the parotid gland . Surg. Glynecol. Obstet. 80:620-630
39 : Katz & Catalano classification: Type I (25%) Type II (14%) Type III(44%) Type IV(14%) Type V(3%) DOI: 10.3346/jkms.2010.25.8.1228
40 : Variations in Intraparotid Portion of Facial Nerve Class 1:Facial nerves without anastomoses between branches after their initial branching from the nerve trunk. (Type 1): Classical variety (Type 2): Variety with precocious branching (Type 3): Rare variety with ladder-like branching . Class 2.:Facial nerves with anastomoses between the cervicotemporal branches (Type 4): Variety with long anastomotic loops (Type 5): Variety with short anastomotic loops between the cervical and temporal branches Source: Illustrated Encyclopedia of Human Anatomic Variation: Opus III: Nervous System Ronald A. Bergman, PhD
41 : Variation of marginal mandibular branch I) The MMB showed one (28%), two (52%), three (18%), or four branches (2%) where it exited the parotid gland. II) Type I (60%) did not communicate with other branches. Type II (40%) communicated with the buccal or cervical branches, or with another branch of the MMB III) The MMB pass the facial artery superficially (42%), deeply in 4%, and on both sides of it in 54% of the facial halves Source: Plastic & Reconstructive Surgery: March 2010 - Volume 125 – Issue 3 - pp 879-889
42 : AGE CHANGES
43 : TESTING OF FACIAL NERVE TOPOGNOSTIC TESTING 1. Schirmer test for lacrimation (GSPN) 2. Stapedial reflex test (Stapedial branch) 3. Taste testing (Chorda tympani nerve) 4. Salivary flow rates & pH (Chorda tympani) ELECTROPHYSIOLOGIC TEST Nerve excitability test (NET) Electromyography(EMG) Maximal stimulation test (MST) Electroneuronography (ENoG) DYES
44 : Schirmer test
45 : ENOG
46 : NET
47 : MST
48 : IDENTIFICATION OF FACIAL NERVES 3 surgical maneuvers used to identify nerve trunk Blood free plane in front of external acoustic meatus Exposure of anterior border of SCM below insertion into mastoid process Peripheral identification of terminal branch of facial nerve (marginal mandibular branch)
49 : COMPLICATION OF FACIAL NERVES DISSECTION Dissected in superficial parotidectomy operation Facial weakness (lower lip on affected side) Temporary and reversible demyelination of nerve fibers
50 : DISORDERS OF FACIAL NERVE
51 : FACIAL NERVES LESION Supranuclear type Features – Paralysis of lower part of face (opposite side) Partial paralysis of upper part of face Normal taste and saliva secretion Stapedius not paralysed
52 : Nuclear type Features – Paralysis of facial muscle (same side) Paralysis of lateral rectus Internal strabismus
53 : Peripheral lesion At internal acoustic meatus Feature – Paralysis of secretomotor fibers Hyper acusis Loss of corneal reflex Taste fibers unaffected Facial expression and movements paralysed Lesion at int acoustic meatus
54 : Injury distal to geniculate ganglion Feature – Complete motor paralysis (same side) No hyper acusis Loss of corneal reflex Taste fibers affected Facial expression and movements paralysed Pronounced reaction of degeneration Lesion distal to geniculate ganglion
55 : Injury at stylomastoid foramen Condition known as Bell’s Palsy
56 : Unilateral involvement Inability to smile, close eye or raise eyebrow Whistling impossible Drooping of corner of the mouth Inability to close eyelid (Bell’s sign) Inability to wrinkle forehead Loss of blinking reflex Slurred speech Mask like appearance of face Loss/ alteration of taste
57 : In case of children the mastoid process not well developed Facial nerve affected by cold exposure or injured during surgical interference
58 : House-Brackmann Facial Nerve Grading System
59 : Trauma: Transverse fractures  (40-50%). Symptoms: hemotympanum (blood behind the tympanic membrane) sensory deafness vertigo
60 : Longitudinal fracture : Symptoms: a) hematorrhea (blood coming out of the external auditory meatus) b) tympanic membrane tear, c) fracture ofexternal auditory canal d) conductive hearing loss
61 : Herpes zoster oticus (Ramsay Hunt syndrome type II) Symptoms: facial paralysis ear pain vesicles, sensorineural hearing loss  vertigo
62 : Acute and chronic otitis media Otitis media is an infection in the middle ear, which can spread to the facial nerve and inflame it, causing compression of the nerve in its canal.
63 : Neurosarcoidosis Facial nerve paralysis, sometimes bilateral, is a common manifestation of neurosarcoidosis  (sarcoidosis of the nervous system), itself a rare condition.
64 : Tumors A tumor compressing the facial nerve result in facial paralysis. Egs:  facial neuromas congenital cholesteatomas hemangiomas, acoustic neuromas  parotid gland neoplasms, or metastases of other tumours.
65 : CONGENITAL ANOMALIES Moebius syndrome(cong facial diplegia) – Abnormal VI ,VII,XII N nuclei – FN absent / smaller – Cong. Extra ocular muscle & facial palsy
66 : Treacher collins syn(mandibulo facial dysostosis) Goldenhars syn(oculoauriculo vertebral dysplasia)
67 : CONCLUSION Facial nerve controls all the involuntary and voluntary movements of facial muscles. The knowledge of surgical anatomy of the facial nerve and its correlations with the parotid gland and facial muscles are very important for an adequate preservation in the cases of surgery in this area. The iatrogenic injury in this facial region is very common. The choice of the surgical approach is very relevant in the parotid surgery because of the extreme anatomic variability of the parotideal area and the functional importance of the branches of facial nerve.
68 : REFERENCES Treatise on applied anatomy-E.Henry Taylor Anatomy of orofacial structures-Brand & Isselhard Textbook of anatomy-Gray’s Textbook of anatomy-Cunningham Clinical anatomy-Richard S.Snell Textbook of applied anatomy-Major .S.Short
69 : THANK YOU Otology could be a dull way of life without the 7th cranial N arrogantly swerving through the temporal bone to the muscles of facial expression “JOHN GROVES”

 

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