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FACIAL NERVE
1. Introduction
2. Embryology
3. Nuclei of origin
4. Course & Relations
5. Branches of facial nerve
6. Functional components
7. Ganglia associated with facial nerve
8. Blood supply
Contents
10.Variations of nerve
11.Testing of facial nerve
12.Identification of facial nerve
13.Complications of facial dissection
14.Facial nerve lesions
15.Acquired & Congenital anomalies
The Facial nerve is the seventh of twelve paired cranial nerves, it is a mixed nerve with motor and sensory roots.
It emerges from the brain stem between the pons and the medulla, controls the muscles of facial expression
It functions in the conveyance of taste sensations from the anterior two thirds of the tongue and oral cavity
It also supplies preganglionic parasympathetic fibres to several head and neck ganglia
Introduction
Embryology
The facial nerve is developmentally derived from the hyoid arch, which is the second branchial arch
The motor division of facial nerve is derived from the basal plate of the embryonic pons
The sensory division originates from the cranial neural crest
Facial nerve course, branching pattern, and anatomical relationships are established during the first 3 months of prenatal life
The nerve is not fully developed until about 4 years of age
The first identifiable Facial Nerve tissue is seen at the third week of gestation- facioacoustic primordium or crest
Facial nerve embryology: 4th week
By the end of the 4th week, the facial and acoustic portions are more distinct
The facial portion extends to placode
The acoustic portion terminates on otocyst
Facial nerve embryology: 5th week
Early 5th week, the geniculate ganglion forms from distal part of primordium
It separates into 2 branches: main trunk of facial nerve and chorda tympani
Facial nerve embryology: 6th week
Near the end of the 5th week, the facial motor nucleus is recognizable
The motor nuclei of VI and VII cranial nerves initially lie in close proximity.
The internal genu forms as metencephalon, it elongates and CN VI nucleus ascends
Facial nerve embryology: 7th week
Early 7th week, geniculate ganglion is well-defined and facial nerve roots are recognizable
The nervus intermedius arises from the ganglion and passes to brainstem. Motor root fibers pass mainly caudal to ganglion
Proximal branches form in the 6th week, posterior auricular branch, branch of digastric
Early 8th week,temporofacial and cervicofacial divisions present
Late 8th week, 5 major peripheral subdivisions present
Nucleui of Origin
1. Motor nucleus of facial nerve (SVE):
It lies in the lower part of the pons
2. Superior salivatory nucleus (GVE):
It lies in the pons lateral to the main motor nucleus of VII and gives rise to secretomotor
parasympathetic fibers that pass in greater superficial petrosal nerve and chorda tympani.
3. Nucleus solitarus (SVA):
It lies in the medulla, receives the taste sensation from the anterior 2/3 of the tongue via the central processes of the cells of the geniculate ganglion of the facial nerve
4. GSA fibers :
Through these fibers to acoustic meatus & back of auricle through communication from auricular
branch of vagus. These fibers terminate in main sensory nucleus & spinal nucleus of 5 th nerve
Facial nerve origin
Internal course: the motor fibres passes dorsally and medially forming a loop around the abducent nucleus in the floor of the 4th ventricle forming facial colliculus
COURSE OF FACIAL NERVE
Superficial origin: at the pontomedullary angle above the inferior cerebellar peduncle.
1- Facial nerve proper (motor): arising from facial motor nucleus in pons.
2- Nervus intermedius: it is the sensory root of facial lies position between the facial proper and vestibulcochlear nerve in the pontocerebellar angle.
Carrying para-sympathetic fibers (from superior salivary nucleus) and taste fibers ( to the solitary nucleus).
The facial nerve is formed mainly of two parts:
Course and relations: I- Intracranial (intrapetrosal) course
II- Extracranial course
I- The intrapetrous course:
The nerve passes laterally with the vestibulocochlear nerve (CN VIII) to the internal auditary meatus. At the bottom of the meatus the nerve enters the facial bony canal where it runs laterally above the vestibule of inner ear.
Reaching the medial wall of the middle ear, it bends sharply backwards above the promontory (forming its genu) where the genicular ganglion is found
It then arches downwards in the medial wall of the middle ear to reach the stylomastoid foramen.
II- Extracranial course:
As it emerges from the stylomastoid foramen, it runs forwards in the substance of the parotid gland crosses the styloid process, the retromandibular vein and the external carotid artery.
It divides behind the neck of the mandible into its terminal branches which come out of the anteromedial surface of the gland.
BranchesIntracranial
Greater petrosal nerveNerve to stapaediusChorda tympani
Intratemporal
IntrameatalLabyrinthineTympanicMastoid nerve
Extracranial
Posterior Auricular NerveDigastric nerveStylohyoid nerve
The five terminal branches
Temporal branchZygomatic branchBuccal branchMarginal mandibular branchCervical branch
Within the facial canal:
1- Nerve to stapedius: supplies the stapedius muscle.
2- Greater superfacial petrosal nerve (GSPN) : arises from the genicular ganglion
The greater superficial petrosal nerve joins the deep petrosal nerve from the sympathetic plexus on the internal carotid artery in carotid canal to form the nerve of the pterygoid canal (vidian nerve) which passes through the pterygoid canal to the pterygopalatine fossa and ends in the pterygo-palatine ganglion
3- Chorda tympani nerve:
It arises from the facial nerve 6 mm above the stylomastoid foramen and runs upwards to perforate the posterior bony wall of the tympanic cavity.
It then passes forwards on the medial surface of the tympanic membrane between its fibrous and mucous layers crossing the handle of the malleus.
It comes out of the tympanic cavity through the petrotympanic fissure to the infratemporal fossa where it joins the lingual nerve.
Through the lingual nerve, it supplies both the submandibular and sublingual salivary glands by secretomotor fibres and taste fibers from the anterior 2/3 of the tongue
II- At the exit from the stylomastoid foramen
1- Posterior auricular nerve: to the auricularis posterior and the occipital belly of the occipitofrontalis muscle.
2- Digastric branch: to the posterior belly of digastric muscle
3- Stylohyoid branch: to the stylohyoid muscle
The temporal branches of the facial nerve (frontal branch of the facial nerve) crosses the zygomatic arch to the temporal region, supplying the auricularis anterior and superior, and joining with the zygomaticotemporal branch of the maxillary nerve, and with the auriculotemporal branch of the mandibular nerve.
TERMINAL BRANCHES
The more anterior branches supply the frontalis, the orbicularis oculi, and corrugator supercilii, and join the supraorbital and lacrimal branches of the ophthalmic.
The temporal branch acts as the efferent limb of the corneal reflex.
The zygomatic branches of the facial nerve (malar branches) run across the zygomatic bone to the lateral angle of the orbit.
Here they supply the Orbicularis oculi, and join with filaments from the lacrimal nerve and the zygomaticofacial branch of the maxillary nerve.
The Buccal Branches of the facial nerve (infraorbital branches), of larger size than the rest of the branches, pass horizontally forward to be distributed below the orbit and around the mouth.
MUSCLE ACTION
Risorius Smile
Buccinator Aids chewing by holding cheeks flat
Levator Labii Superioris Elevates upper lip
Levator labii superioris alaeque nasi Snarl
Levator Anguli Oris Soft smile
Nasalis Flare Nostrils
Orbicularis oris muscle Purse Lips
Depressor Septi Nasi Depresses Nasal Septum
Procerus Moves Skin of Forehead
The buccal branch supplies these muscles
The marginal mandibular branch of the facial nerve passes forward beneath the platysma and depressor anguli oris.
It supplies the muscles of the lower lip and chin, and communicating with the mental branch of the inferior alveolar nerve.
The cervical branch of the facial nerve runs forward
It forms a series of arches across the side of the neck over the suprahyoid region.
One branch descends to join the cervical cutaneous nerve from the cervical plexus; others supply the Platysma. Also supplies the depressor anguli oris.
Branches
Branches of communication Branches of distribution
Internal acoustic meatus Vestibulocochlear nerve
Geniculate ganglion A. Greater petrosal nerve B. Lesser petrosal nerve C. External petrosal nerve
Facial canal Vagus nerve
Stylomastoid foramen IX & X cranial nerveGreater auricular nerveAuriculotemporal nerve
Behind ear Lesser occipital
Face V nerve
Neck Transverse cutaneous nerve
Branches of Communication
Branches of Distribution
Facial canal A. Nerve to stapedius
B. Chorda tympani
In face A. Temporal
B. Zygomatic
C. Buccal
D. Marginal mandibular
E. Cervical
Stylomastoid foramen
A. Posterior auricular
B. Nerve to stylohyoid
C. Nerve to digastric (posterior belly)
Facial Nerve: Functional Components
Special Visceral Efferent/Branchial Motor
General Visceral Efferent/Parasympathetic
General Sensory Afferent/Sensory
Special Visceral Afferent/Taste
Special Visceral Efferent/Branchial Motor
Premotor cortex motor cortex corticobulbar tract bilateral facial motor nuclei (pons) facial muscles
Stapedius, stylohyoid, posterior digastric, buccinator
General Visceral Efferent/ParasympatheticSuperior salivatory nucleus (pons)
nervus intermedius
greater/superficial petrosal nerve
facial hiatus/middle cranial fossa
joins deep petrosal nerve (symp fibers from cervical plexus)
through pterygoid canal (as vidian nerve)
pterygopalatine fossa
spheno/pterygopalatine ganglion
postganglionic parasympathetic fibers
joins zygomaticotemporal nerve(V2)
lacrimal gland & seromucinous glands of nasal and oral cavity
Superior salivatory nucleus
nervus intermedius
chorda tympani
joins lingual nerve
submandibular ganglion
postganglionic parasympathteic fibers
submandibular and sublingual glands
General Sensory Afferent/Sensory
Sensation to auricular concha, EAC wall, part of TMJ, postauricular skin
Through Cell bodies in geniculate ganglion
Special Visceral Afferent/TastePostcentral gyrus
nucleus tractus solitarius
nervus intermedius
geniculate ganglion
chorda tympani
joins lingual nerve
anterior 2/3 tongue, soft and hard palate
GANGLIA ASSOCIATED WITH THE FACIAL NERVE
Geniculate ganglion
Submandibular ganglion
Pterygopalatine ganglion
Geniculate Ganglion
The geniculate ganglion (from Latin genu, for "knee") is an L-shaped collection of fibers and sensory neurons of the facial nerve located in the facial canal of the head.
It receives fibers from the motor, sensory, and parasympathetic components of the facial nerve and sends fibers that will innervate the lacrimal glands, submandibular glands, sublingual glands, tongue, palate, pharynx, external auditory meatus, stapedius, posterior belly of the digastric muscle, stylohyoid muscle, and muscles of facial expression.
Submandibular Ganglion
The submandibular ganglion is small and fusiform in shape. It is situated above the deep portion of the submandibular gland, on the hyoglossus muscle, near the posterior border of the mylohyoid muscle.
The ganglion 'hangs' by two nerve filaments from the lower border of the lingual nerve (itself a branch of the mandibular nerve, CN V3). It is suspended from the lingual nerve by two filaments, one anterior and one posterior. Through the posterior of these it receives a branch from the chorda tympani nerve which runs in the sheath of the lingual nerve.
Pterygopalatine Ganglion
The pterygopalatine ganglion (meckel's ganglion, nasal ganglion or sphenopalatine ganglion) is a parasympathetic ganglion found in the pterygopalatine fossa.
It's largely innervated by the greater petrosal nerve (a branch of the facial nerve); and its axons project to the lacrimal glands and nasal mucosa
Facial Nerve blood supply
The facial nerve gets it’s blood supply from 4 vessels:
Anterior inferior cerebellar artery – at the cerebellopontine angle
Labyrinthine artery (branch of anterior inferior cerebellar artery) – within internal acoustic meatus
Superficial petrosal artery (branch of middle meningeal artery) – geniculate ganglion and nearby parts
Stylomastoid artery (branch of posterior auricular artery) – mastoid segment
Posterior auricular artery supplies the facial nerve at & distal to stylomastoid foramen
Venous drainage parallels the arterial blood supply
Variations of Facial Nerve1. Buccal branch usually single, two branches in 15% cases
2. Marginal mandibular branch – pass bellow the lower border of mandible, incidence varying between 20-50%
3. Cervical branch – 20% cases, two branches
4. Katz and Catalano reported cases (3%) presenting two main trunks, known as the major and minor trunks of facial nerve.
5. Baker and Conley reported trifurcation, quadrifurcation, or even a plexiform branching pattern of the trunk of the facial nerve
Patterns of branching of Facial Nerve
Classified by Davis et al (1956)
1. Type I facial nerve (straight branching) with variations.
Type IA
I). Zygomatic sending a loop to itself
ii). Absent zygomatic loop
Type IB
iii). Buccal nerve arising from upperdivision & mandibular sending a loop to itself
iv). Mandibular loop is absent.
Type II facial nerve major connection betweenbuccal & zygomatic nerves
Type III facial nerve with major connection betweenbuccal & any other nerve.
Type IIIA i). Anastomosis between zygomatic & buccal nerveii). between buccal & upper division iii). between buccal and lower division
Type IIIBiv). between buccal nerve (arising from mandibular) &zygomatic nerve
Type IIICv) Connection between buccal & marginal mandibularvi). Connection between buccal nerve arising fromupper division & lower division .vii). Type III C with additional anastomosis between upper &lower divisions .
Type IV Complex branching pattern.
Type IVA
i). Buccal nerve arising from upper divisionii). No anastomosis between buccal nerve & upper division (V).
TYPE IVB
iii). Buccal nerve arising from both division.iv). Buccal nerve arising from upper division only (V).
Type V Two main trunks.
i). Type VA upper & lower division arising from major trunk,buccal nerve arises from both divisions, minor trunk joinslower division.
ii). Type VB upper division from major & lower from minortrunk, buccal nerve arises from both division.
iii). Type VC upper & lower division both arise from the majortrunk & minor trunk enters the upper division as a separatebranch.
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
Child Adult
Chorda tympani may exit through Stylomastoid Foramen
Chorda tympani exit proximal to Stylomastoid Foramen
2nd genu is more acute and lateral
2nd genu is less acute and medial
Nerve trunk is more anterior and lateral on exit through Stylomastoid Foramen
Nerve trunk is less anterior and deeper
Nerve very superficial over angle of mandible
Nerve less superficial over angle of mandible
Age Changes
Testing of Facial Nerve Branches
Testing the temporal branches of the facial nerve
To test the function of the temporal branches of the facial nerve, a patient is asked to frown and wrinkle his or her forehead.
Testing the Zygomatic branches of the facial nerve
The patient is asked to close their eyes tightly.
Testing the buccal branches of the facial nerve
Puff up cheeks (buccinator)
Smile and show teeth (orbicularis oris) Tap with finger over each cheek to detect ease of air expulsion on the affected side
The marginal mandibular nerve may be injured during surgery in the neck region, especially during excision of the submandibular salivary gland or during neck dissections.
Damage to facial nerve is possible in severe maxillofacial surgeries with basilar skull fractures anywhere in the area of course of the nerve and would result in ipsilateral paralysis of the muscles of facial expression
Of concern to the surgeon is the close proximity of the main trunk of facial nerve where it exits the stylomastoid foramen and mandibular condyle
Applied Surgical anatomy of Facial Nerve in
Oral & Maxillofacial Surgery
After exiting the stylomastoid foramen, which is situated posterolateral to stylomastoid process, the nerve enters the substance of parotid gland where it divides into its upper and lower divisions just posterior to the mandible
The approximate distance from the lowest pointof the external bony auditory meatus to the bifurcation of the facial nerve is 2.3 cm
Posterior to the parotid gland,the nerve is atleast 2cm deep into the skin surface,from this point the two branches curve around the posterior mandible,where they form plexus between the parotid gland and the masseter muscle
The terminal branches of facial nerve then spread in a fan like fashion as five separate nerves
Temporal branch :
It exits the parotid gland anterior to superficial temporal artery
During an open approach to the TMJ, violation of this branch is possible
Zygomatic Branch :
Its course is antero superior crossing the zygomatic bone
Inadvertent damage may occur to this nerve during open reduction of zygomatic arch or with the use of a byrd screw or zygomatic hook during closed approaches
Buccal Branch:
It runs almost horizontally and will often divide into separate branch above and below parotid duct as it runs anteriorly
Injury is possible in association with soft tissue trauma to the cheek region
Marginal mandibular branch:
It extends anteriorly and inferiorly within the substance of parotid gland, there may be two or three branches of this nerve.
These branches run anteriorly parallel to inferior border of mandible and in some cases the course of the nerve is above the inferior border.
In essentially all cases the nerve is located above the inferior border of mandible beyond the facial artery.
The marginal mandibular branch is an important structure encountered at the inferior border of the mandible just beneath the platysma muscle fibres during an open approach to the mandibular angle and body area.
For this reason, an initial incision made approximately 1 to 1.5cm below the inferior border which prevents direct exposure or trauma to the nerve
Cervical Branch:
The cervical branch exits the parotid gland above its inferior pole and runs downwards underneath the platysma muscle
The surgeon must be mindful of the facial nerves intimate involvement with the TMJ, specially when performing surgical approaches to the joint.
The temporal and zygomatic branches are at increased risk during pre auricular approach and the marginal mandibular branch during submandibular approach
The intra oral approach to the TMJ has minimal risk to the branches of facial nerve which is its major advantage
Complications of parotid surgery
Intra-operative or post-operative
Post-operative complications can be classified as early and late (or long-term) complications.
Intra-operative complications of parotid gland surgery
Intra-operative complications of parotid gland surgery comprise transection of the facial nerve or one of its branches, rupture of the capsule of a parotid tumour or incomplete surgical resection thereof.
The surgeon has to immediately recognize an intra-operative complication and management thereof must be performed without delay.
In the event of nerve injury, immediate nerve repair is mandatory. Once the segments have been fully mobilized and brought together without tension, the two ends should be sutured together.
The nerves are gently grasped with a Bishop forceps. With an 8-0 nylon suture and a GS-8 needle, the epineurium is grasped at one end and then sutured to the other, avoiding deep cuts in the perineurium
Three sutures are usually adequate to maintain the anastomosis
As an alternative to sutures, the surgeon may use fibrin tissue adhesive.
If the nerve length is inadequate, a nerve graft of the greater auricular nerve, can be applied
Post-operative complications of parotid gland surgery
Post-operative facial nerve dysfunction involving some or all of the branches of the nerve is the most frequent early complication of parotid gland surgery.
Temporary facial nerve paresis, involving all or just one or two branches of the facial nerve, and permanent total paralysis have occurred.
The cases of transient facial nerve paresis generally resolved within 6 months
The incidence of facial nerve paralysis is higher with total, than with superficial parotidectomy, which may be related to stretch injury or as result of surgical interference with the vasa nervorum
The branch of the facial nerve most at risk for injury during parotidectomy is the marginal mandibular branch.
Older patients appear to be more susceptible to facial nerve injury
However, eye protection must be ensured. If facial paresis causes incomplete closure of the eye, the patient must be advised to use ophthalmic moisture drops frequently during the day and an ophthalmic ointment and eye protection at night.
Regular follow-up with an ophthalmologist is mandatory
Moreover, use of botulinum toxin to induce temporary ptosis avoids the need of surgical tarsorrhaphy.
3 surgical maneuvers used to identify nerve trunk
A. Blood free plane in front of external acoustic meatus
B. Exposure of anterior border of SCM below insertion into mastoid process
C. Peripheral identification of terminal branch of facial nerve (marginal mandibular branch)
Identification of Facial Nerve
Disorders of Facial Nerve
1. Supra nuclear type:
Features:
a) Paralysis of lower part of face (opposite side)b) Partial paralysis of upper part of facec) Normal taste and saliva secretiond) Stapedius not paralysed
Facial Nerve Lesions
2. Nuclear type:
Features:
a) Paralysis of facial muscle (same side)
b) Paralysis of lateral rectus
c) Internal strabismus
3. Peripheral lesion
a) At internal acoustic meatus
Features:
i. Paralysis of secretomotor fibers
ii. Hyper acusis
iii. Loss of corneal reflex
iv. Taste fibers unaffected
v. Facial expression and movements paralysed
Lesion at int acoustic meatus
b) Injury distal to geniculate ganglion
Features:
i. Complete motor paralysis (same side)
ii. No hyper acusis
iii. Loss of corneal reflex
iv. Taste fibers affected
v. Facial expression and movements paralysed
vi. Pronounced reaction of degeneration
Lesion distal to geniculate ganglion
c) Injury at stylomastoid foramen
• Condition known as Bell’s Palsy
Background of BELL’S PALSY
First described more than a century ago by Sir Charles Bell
Yet much controversy still surrounds its etiology and management
.Bell palsy is certainly the most common cause of facial paralysis worldwide
Demographics of Bells palsy
Race: slightly higher in persons of Japanese descent. Sex: No difference exists Age: highest in persons aged 15-45 years.
Bell palsy is less common in those younger than 15 years and in those older than 60 years.
Pathophysiology of Bells palsy
Main cause of Bell's palsy is latent herpes viruses (herpes simplex virus type 1 and herpes zoster virus), which are reactivated from cranial nerve ganglia
Polymerase chain reaction techniques have isolated herpes virus DNA from the facial nerve during acute palsy
Inflammation of the nerve initially results in a reversible neurapraxia
Herpes zoster virus shows more aggressive biological behaviour than herpes simplex virus type1
Bell's phenomenon is the upward diversion of the eye ball on attempted closure of the lid is seen when eye closure is incomplete.
I. Unilateral involvement
II. Inability to smile, close eye or raise eyebrow
III. Whistling impossible
IV. Drooping of corner of the mouth
V. Inability to close eyelid (Bell’s sign)
VI. Inability to wrinkle forehead
VII. Loss of blinking reflex
VIII.Slurred speech
IX. Mask like appearance of face
X. Loss/ alteration of taste
Features of Bell’s Palsy
Fore head
Diagnosis of Bells palsy
By exclusion
Criteria
Paralysis or paresis of all muscle groups of one side of the face
Sudden onset
Absence of signs of CNS disease
Absence of signs of Ear disease
Management of Bells palsy
It focuses on protecting the cornea from drying and abrasion due to problems with lid closure and the tearing mechanism.
Lubricating drops should be applied hourly during the day and a simple eye ointment should be used at night.
Eye care
Treatment consists of Infra-red radiation on affected side of the face at 2 ft (60cm) ,followed by interrupted galvanism on affected side
Treatment was given daily at first few weeks & later thrice weekly.
All patients are instructed to massage the face daily
There is general agreement that 70-80% of these patients recover completely,while the reminder develop various sequelae within one to three months
Medical treatment
Corticosteroids :
Prednisolone 1 mg/kg/day 7-10 days Corticosteroids combine with antiviral drug is better
Acyclovir 400 mg 5 times/day Famciclovir and valacyclovir 500 mg bid
Surgical treatment
Facial nerve decompression
Indication:
Completely paralysis
ENoG less than 10% in 2 weeks
Appropriate time for surgery is 2-3 weeks after paralysis
Causes of Facial Nerve Paralysis
Peripheral nerve causes (Facial muscle paralysis with forehead affected)
Lyme Disease
Otits Media or Mastoiditis
Ramsay Hunt Syndrome
Autoimmune Polyneuropathy (e.g. Guillain-Barre Syndrome, typically bilateral)
Head or Neck Mass Lesion (e.g. Cholesteatoma)
Central/Supranuclear causes (Facial muscle paralysis with forehead spared)
Cerebral mass lesion (e.g. tumor)
Cerebrovascular Accident (typically with ipsilateral Hemiparesis or Hemiplegia)
Multiple Sclerosis
Traumatic causes
Cortical injury
Temporal BoneFracture
Brain Stem injury
Penetrating middle ear injury
Barotrauma
Altitude paralysis Scuba Diving
Endocrine causes
Diabetes Mellitus
Hyperthyroidism
Pregnancy
Hypertension
Alcohol Abuse (Alcoholic Neuropathy)
Infectious Causes
Malignant Otitis Externa (skull base Osteomyelitis)
Acute or Chronic Otitis Media Gradenigo's Syndrome (CN V or CN VI)
Mastoiditis
Varicella Zoster Virus (Chicken Pox)
Herpes Zoster Oticus (Ramsey-Hunt Syndrome) Herpetic Vesicles at auricle and external canal
HIV Infection
Influenza Vaccine and Influenza
Parotitis
Meningitis or Encephalitis
Mumps
Mononucleosis
Leprosy
Coxsackie virus infection
Syphilis
Tuberculosis
Botulism
Mucormycosis
Causes due toTumors
Facial Nerve neuroma
Cholesteatoma
Glomus jugular tumor
Primary Temporal Bone tumors
Meningiomas
Hemangioblastoma
Hemangioma
Pontine glioma
Parotid tumor
A tumor compressing the facial nerve result in Facial paralysis
Birth Causes
Facial Nerve Injury from Birth Trauma
Trauma (forceps delivery)
Congenital Facial Palsy
Mobius syndrome
Cardiofacial syndrome
Toxic Causes:
Thalidomide
Tetanus
Diphtheria
Carbon Monoxide
Lead Intoxication
Idiopathic Causes:
Myasthenia Gravis
Guillain-Barre Syndrome
Sarcoidosis
Familial Bell's Palsy
Iatrogenic Causes:
Antitetanus serum
Vaccine treatment for Rabies
Mandibular block anesthesia
Head and neck surgery
Evaluation of Facial paralysis
Clinical feature Central VS Peripheral facial paralysis Complete head and neck examination Cranial nerve evaluation
Electrodiagnostic testing
Topographic diagnosis
Central facial paralysis
Upper motor neuron lesion Movements of the frontal and upper orbicularis oculi tend to be spared
Because of uncrossed contributions from ipsilateral supranuclear areas
Involvement of tongue
Involvement of lacrimation and salivation
Peripheral paralysis
Lower motor neuron lesion
At rest :less prominent wrinkles on forehead of affected side, eyebrow drop, flattened nasolabial fold, corner of mouth turned down
Unable to : wrinkle forehead, raise eyebrow, wrinkle nasolabial fold, purse lips, show teeth, or completely close eye
House-Brackmann grading system
Grade I - Normal Grade II - Mild dysfunction, slight weakness on close inspection, normal symmetry at rest Grade III - Moderate dysfunction, obvious but not disfiguring difference between sides, eye can be completely closed with effort Grade IV - Moderately severe, normal tone at rest, obvious weakness or asymmetry with movement, incomplete closure of eye Grade V - Severe dysfunction, only barely perceptible motion, asymmetry at rest Grade VI - No movement
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 TESTS
Nerve excitability test (NET)Electromyography(EMG) Maximal stimulation test (MST) Electroneuronography (ENoG)
DYES
Testing of Facial Nerve
Topographic Diagnosis
To determine the anatomical level of a peripheral lesion
Lacrimation Geniculate ganglion
Stapedius reflex motor nerve of stapedius muscle
Taste chorda tympani
Schirmer's Test
Geniculate ganglion & petrosal nerve function test
Schirmer’s test +ve when
Affected side shows less than half the amount of lacrimation seen on the normal side
Sum of the lengths of wetted filter paper for both eyes less than 25 mm
Lesion at or proximal to the geniculate ganglion
Schirmer's Test
Stapedius reflex
Nerve to stapedius muscle test
Impedence audiometry can record the presence or absence of stapedius muscle contraction to sound stimuli 70 to 100 db above hearing threshold
An absence reflex or a reflex less than half the amplitude is due to a lesion proximal to stapedius nerve
Taste (Electrogustometry)
Chorda tympani nerve test
Solution of salt, sugar, citrate, quinine or Electrical stimulation
Compares amount of current require for a response each side of tongue
Normal : difference < 20 uAmp (thresholds differening by more than 25%= abnormal)
Total lack of Chorda tympani : No response at 300 uAmp
Disadvantage : False +ve in acute phase of Bell’s palsy
Maximum stimulation Test: MST:
Indication: complete paralysis<3wks
Interpretation:
Marked weakness or no muscle contraction:
advanced degeneration with guarded prognosis
Electroneurography: ENoG
Indication: complete paralysis<3wks
Interpretation: < 90% degeneration: prognosis is good; > or = 90%: prognosis is a question
Limitation: False-positive results in deblocking phase.
Electromyography: EMG
Indication: Acute paralysis less than 1 week or chronic paralysis longer than 2 weeks
Interpretation:
Active mu: intact motor axons
Mu + fibrillation potentials: partial degeneration
Polyphasic mu: regenerating nerve
Limitation: cannot assess degree of degeneration or prognosis for recovery
Symptoms:
Facial paralysis
Ear pain
Vesicles
Sensorineural
hearing loss
Vertigo
Herpes zoster oticus Ramsay Hunt syndrome type II
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.
Neurosarcoidosis
Facial nerve paralysis, sometimes bilateral, is a
common manifestation of neurosarcoidosis
(sarcoidosis of the nervous system)..
Itself a rare condition.
Moebius syndrome (congenital facial diplegia) Abnormal VI ,VII,XII Nerve nuclei Facial Nerve absent / smaller Congenital Extra ocular muscle & facial palsy
Congenital Facial nerve palsy
Cardiofacial Syndrome
Unilateral facial paralysis involving only the lower lip and congenital heart disease
The facial paralysis in these patients involves only those muscles concerned with pulling the lower lip downwards and outwards
These are the mentalis, depressor labii inferioris and depressor anguli oris muscles
All are supplied by the mandibular marginal branch of the facial nerve.
Lesions of this nerve have been recognized in adultsand children for many years The paralysis is only recognizable when the patienttalks, smiles or cries
Treacher collins syndrome (mandibulo facial dysostosis)
There is a set of typical symptoms within Treacher Collins Syndrome
The OMENS classification was developed as a comprehensive and stage-based approach to differentiate the diseases. O; orbital asymmetry M; mandibular hypoplasia E; auricular deformity N; nerve development and S; soft-tissue disease
Facial Nerve involvement in Treacher collins syndrome
N0: No facial nerve involvement
N1: Upper facial nerve involvement (temporal or zygomatic branches)
N2: Lower facial nerve involvement (buccal, mandibular or cervical)
N3: All branches affected
Goldenhars syndrome (oculoauriculo vertebral dysplasia)
It is a wide spectrum of congenital anomalies that involves structures arising from the first and second branchial arches.
Features of hemi facial microsomia, anotia, vertebral anomalies, congenital facial nerve palsy.
Conclusion
Surgeons have to pay attention to minimize the risk of complication during parotidectomy.The best means of reducing iatrogenic facial nerve injury, in parotid surgery, still remains a clear understanding of the anatomy, good surgical technique with the use of multiple anatomic landmarks. Pre-operative discussion and consent for surgery, tailored according to the age and health of the patient as well as the behavior of the tumor, are mandatoryFurthermore, the patient has to be informed about the cosmetic sequelae of the incision and all patients have to be told that facial nerve paralysis or paresis is possible and can be partial or total, temporary or permanent.
References
Fonseca & Walker : Maxillo FacialTrauma 2nd Edition Vol 1 & 2
Grays Anatomy : 39th Edition
Netters : Colour Atlas of Anatomy
International journal of Oral & maxillofacial Surgery
Guided by:
Dr.S.M.Nooruddin MDS.,Professor & HODDept of Oral & Maxillofacial Surgery
Dr.K.Surekha MDS.,Associate Professor
Dr.G.Sudhakar MDS.,Assistant Professor
Presented by:Dr.T.Roger paul 1st yr PG GDC&H,VIJAYAWADA.
THANK YOU
