FACIAL NERVE AND ITS APPLIED ASPECTSDR.SADAF SYED

INTRODUCTION It’s the 7th cranial nerve It is a mixed nerve Composed of approximately 10,000 neurons,

7,000 of which are myelinated and innervate the nerves of facial expression.

Three thousand of the nerve fibers are somatosensory and secretomotor and make up the nervus intermedius.

The facial nerve innervates 14 of the 17 paired muscle groups of the face on their deep side.

EMBRYOLOGY

• Main pattern of the nerve's complex course, branching pattern, and relationships is established during the first 3months of prenatal life.

• During this period the muscles of expression also differentiate, become functional, and actively contract.

• Important steps in facial nerve development occur throughout gestation and the nerve is not fully developed until approximately 4 years after•  In the newborn, the facial nerve anatomy approximates that of an adult, except for its location in the mastoid, which is more superficial.

Time during gestation that anatomical structures appear

Week 3 Collection of neural crest cells to become seventh cranial nerve identifiableWeek 5 Chorda tympani, greater petrosal, VII motor nucleusWeek 6 External genu, postauricular branch, branch to posterior belly digastricWeek 7 Geniculate ganglion, nervus intermediusWeek 8 Stapedius nerve, temporofacial and cervicofacial part of extracranial facial nerve becomes apparentEnd of week 8 Rest of terminal branches of VII formWeek 7-8 Myoblasts that will form the facial muscles are notedWeek 12 All facial muscles are identifiable.

NUCLEAR ORIGINMotor nucleus of

facial nerve

Nucleus of tractus solitarius

Superior salivatory nucleus

Spinal nucleus of trigeminal

nerve

Lower part of pons, in front of abducent nerve nucleus.Fibres for muscles of second brachial arch arise here

Lies in pons,lateral to motor nucleusPreganglionic parasympathetic secretomotor fibres.

Receive fibres of taste sensation

Lies in medullaRecieves fibres for pain and temperature sensation from external auditory meatus

•(2and

•(3

•(4)

SENSORY COMPONENT

Afferent taste fibers from the chorda tympani nerve, from the anterior two thirds of the tongue; Preganglionic

parasympathetic

innervation to the

submandibular,

sublingual, and lacrimal

glands.

The nervus intermedius also has a small cutaneous sensory component from afferent fibers originating from the skin of the auricle and postauricular area.

) Taste fibers from soft palate via the palatine

and greater petrosal nerves;

Nervus intermedius and vestibulocochlear nerve

The facial nerve and the nervus intermedius enter the IAC with the vestibulocochlear nerve.

. The vestibulocochlear nerve enters the IAC inferiorly .along the roof of the IAC.

A useful mnemonic for remembering this

relationship is "Seven-up over Coke.

COURSE OF FACIAL NERVE

Intracranial IntratemporalIntrameatalLabyrinthinTympanicMastoid

Extracranial

FUNCTIONAL COMPONENTS1.SPECIAL VISCERAL COMPONENTMotor to muscles derived from 2nd brachial arch,

i.e muscles of facial expression

2.GENERAL VISCERAL EFFERENTSecretomotor fibres

a) Submandibular and sublingual salivary gland

b) Lacrimal glandc) Mucous glands of the nose, palate and pharynx

3. SPECIAL VISCERALAFFERENT Carries taste sensation from anterior 2/3rd of

tongue

4. GENERAL SOMATIC AFFERENT• Proprioceptive impulses from 2nd arch

muscles • Sensation from external auditory meatus

The lesser petrosal nerve Secretory fibers to the parotid gland. This nerve carries parasympathetic contributions from the tympanic plexus (from CN IX) and the nervus intermedius

In the pterygoid canal

Axons from this nerve synapse in the pterygopalatine ganglion;

postganglionic parasympathetic fibers,

Which are carried via branches of the maxillary (V2) divisions of the

trigeminal nerve (CN V),

Innervate the lacrimal gland and mucus glands of the nasal and oral

cavities. .

CHORDA TYMPANI Parasympathetic

Arises : distal to the geniculate ganglion, within the facial canal, 6mm above

stylomastoid foramen

Runs laterally in the middle ear, between the incus and the handle of the

malleus.

Makes an anteromedial turn,from gg,exits the temporal bone into middle cranial fossa

Through faramen lacerum exits through the petrotympanic fissure (ie, canal of

Huguier)

Enter infra temporal fossa ,forming pterygopalatine ganglion

•

•The chorda tympani is the terminal branch of the nervus intermedius.

SuppliesMucous glands of oral cavity.

Lacrimal gland.

•The chorda tympani nerve carries preganglionic secretomotor fibers to the submaxillary and sublingual glands.

• Parasympathetic Fibres of chorda tympani stay with lingual nerve (Trigeminal Nerve )

• Main Body of nerve leaves to innervate ant 2/3 of tongue

Intratemporal

Travel through internal acoustic meatus, 1 cm long opening in petrous part of temporal bone

In temporal bone the roots leave the internal acoustic meatus and enter facial canal

Facial canal is a z shaped canal

Intrameatal

.

Labyrinthine• The location of this segment of the nerve immediately posterior to the cochlea

GENICULATE GANGLION

The facial nerve changes direction to form the first genu , marking the location of the geniculate ganglion.

The geniculate ganglion is formed by the juncture of the nervus intermedius and the facial nerve into a common trunk. Additional afferent fibers from the anterior two thirds of the tongue are added to the geniculate ganglion from the chorda tympani.

Three nerves branch from the geniculate ganglion:

The greater superficial petrosal n The external petrosal nerve.

Tympanic (horizontal) segment Extends from the geniculate ganglion to the horizontal semicircular canal and is 8-11mm in length. The nerve passes behind the cochleariform process and the tensor tympani. The nerve lies against the medial wall of the cavum tympani, above and posterior to the oval window. The wall can be very thin or dehiscent in this area, and the middle ear mucosa may lay in direct contact with the facial nerve sheath.

The distal portion of the facial nerve emerges from the middle ear between the posterior wall of the external auditory canal and the horizontal semicircular canal. distal to the pyramidal eminence, where the facial nerve makes a second turn (marking the second genu)..The distal aspect of the tympanic segment can be surgically located via a facial recess approach. The chorda tympani nerve can be used to identify the nerve when performing a facial recess approach

TYMPANIC PART

Mastoid segment

The second genu marks the beginning of the mastoid segment.

It is lateral and posterior to the pyramidal process. The nerve continues vertically down the anterior wall of the mastoid process to the stylomastoid foramen.

It is the longest part of the intratemporal course of the facial nerve, approximately 10-14mm lon.

Landmarks for identifying the facial nerve in the mastoid :

The horizontal semicircular canal, The fossa incudis, and The digastric ridge.

The second genu of the facial nerve runs inferolateral to the lateral semicircular canal. This is a relatively constant relationship

SEGEMENT LOCATION LENGTH, mm

SUPRANUCLEAR CEREBRAL CORTEX --BRAIN STEM Motor nucleus of VII nerve,

Superior salivatory nucleus of tractus solitarius

--

INTRACRANIAL

MEATAL SEGEMENT

Brainstem to internal auditory canal

13-15

8-10 mmLABYRINTHINESEGEMENT

Fundus to IAC 3-4

TYMPANIC Geniculate ganglion to pyramidal eminence

8-11

MASTOID SEG. Pyramidal process to stylomastoid foramen

10-14

Stylomastoid foramen to pes anserinus

15-20

Post. Auricular nerveArises just below stylomastoid foramen

Divides into two branches

a)Auricular BranchMuscles of auricle

b) Occipital branch :Occipital belly of occipito frontalisRuns forward through a short

canal

Extracranial The facial nerve exits the fallopian canal via the

stylomastoid foramen. 1.3 cm from stylomastoid foramen to where it

divides into Temporofacial and cervicofacial division.

The nerve travels between the digastric and stylohyoid muscles and enters the parotid gland.

A sensory branch exits the nerve just below the stylomastoid foramen and innervates the posterior wall of the external auditory canal and a portion of the tympanic membrane

After emerging from the stylomastoid foramen, the facial nerve enters the parotid gland, where it branches at the pes anserinus.

Once it has exited the fallopian canal at the stylomastoid foramen, the facial nerve gives off several rami before it divides into its main branches.

Below the stylomastoid foramen, the posterior auricular nerve leaves the facial nerve and innervates the postauricular muscles. Two small branches innervate the stylohyoid muscle and posterior belly of the digastric muscle.

The facial nerve crosses lateral to the styloid process and penetrates the parotid gland. The nerve lies in a fibrous plane that separates the deep and superficial lobes of the parotid gland.

Nerve to post. Belly of diagastric

Arises near the origin of posterior auricular nerve Also gives branch to stylohyoid muscles

In the parotid gland, the nerve divides at the pes anserinus into 2 major divisions;• the superiorly directed temporal-facial and• the inferiorly directed cervicofacial branches

TEMPORAL BRANCH

ZYGOMATIC BRANCH

BUCCAL BRANCH

MARGINAL MANDIBULAR BRANCH

CERVICAL BRANCH

TERMINAL BRANCHES

BUCCAL BRANCHES : UPPER BRANCH• Zygomaticus Major • Zygomaticus Minor Levators of the upper lipLOWER BRANCH• Buccinator• Orbicularis Oculi

Temporal BranchRuns across zygomatic arch Supplies •Muscles of Ear• Frontal Belly of occipito frontalis• Corrugator Supercilli

ZYGOMATIC BRANCH • Below and parallel to zygoma and orbicularis oculi

MARGINAL MANDIBULAR BRANCH

• Runs downwards and forward below the angle of mandible • Curves upward acros s the base of mandible• Supply : Muscles of the lower lip and chinCERVICAL

BRANCHDownwards and forwards to the front of neck and supplies the platysma

VESTIBULAR –

COCHLEAR NERVE ,

AT THE INTERNAL ACOUSTIC MEATUS

SYMPATHETIC

PLEXUS AROUND MIDDLE

MENINGEAL

ARTERY,AT GG9th,10th,CR

ANIAL N. BELOW

THE STYLOID

FORAMEN

AURICULAR BRANCH OF VAGUS NERVE, IN

THE FACIAL CANAL

COMMUNICATING BRANCHES

The temporal and marginal mandibular branches are at highest risk during surgical procedures and are usually terminal connections without anastomotic connections

Surgical landmarks to the facial nerve The tympanomastoid suture line, The tympanomastoid suture line lies between the mastoid and tympanic segments of the temporal bone and is approximately 6-8mm lateral to the stylomastoid foramen.

The tragal pointer, The nerve is usually located inferior and medial to the pointer. and

The posterior belly of the digastric muscle.The main trunk of the nerve can also be found midway between (10mm posteroinferior to) the cartilaginous tragal pointer of the external auditory canal and the posterior belly of the digastric muscle.

• The topographic trajectory of the frontal and/or marginal branches should be identified during a submandibular gland excision, and/or neck dissection.

• The frontal branch can be roughly located along a line extending from the attachment of the lobule (approximately 5mm below the tragus), anterior and superior to a point 1.5cm above the lateral aspect of the ipsilateral eyebrow.

CONTD**

A line drawn between the mastoid tip and the angle of the mandible can serve as a useful landmark for the superior limits of a neck dissection.

Removal of parotid tissue inferior to this line can be performed relatively safely.

The topographic trajectory of the frontal and/or marginal branches should be identified during a rhytidoplasty, submandibular gland excision, and/or neck dissection. The frontal branch can be roughly located along a line extending from the attachment of the lobule (approximately 5mm below the tragus), anterior and superior to a point 1.5cm above the lateral aspect of the ipsilateral eyebrow.[6, 7]

Surgical landmarks to the facial nerve include the tympanomastoid suture line, the tragal pointer, and the posterior belly of the digastric muscle. The tympanomastoid suture line lies between the mastoid and tympanic segments of the temporal bone and is approximately 6-8mm lateral to the stylomastoid foramen. The main trunk of the nerve can also be found midway between (10mm posteroinferior to) the cartilaginous tragal pointer of the external auditory canal and the posterior belly of the digastric muscle. The nerve is usually located inferior and medial to the pointer.During surgical dissection, the surgeon may encounter a branch from the occipital artery that lies lateral to the facial nerve. Brisk bleeding at this time may be a sign that the nerve is in close proximity; hemostasis should be obtained using bipolar electrocautery, and further dissection should proceed cautiously. The styloid process is deep to the main trunk of the nerve.

In the infant and young child, these landmarks are not applicable because of differences in the rate of anatomic development of the parotid gland and mastoid.

The modified Blair incision most commonly used in adults is often avoided in children because the facial nerve is located more superficially, and the risk of injury is increased with elevation of the skin flaps.

APPLIED ASPECT OF FACIAL NERVE

“LEVEL OF LESION”

AT INTERNAL ACOUSTIC MEATUS

The close anatomic association between the facial nerve, the nervus intermedius, and the

vestibulocochlear nerve at the level of the CPA and in the IAC

Disturbances in tearing, taste, salivary gland flow, hearing, balance, and facial function.

• Tinnitus, • Unilateral hearing loss,• Balance disturbances .

• Large acoustic schwannomas may progress to involve

the facial nerve and even CN V, CN IX, CN X, and CN XI.

Unilateral conditions• Bells palsy• Sarcoidosis • Leprosy• Lymes Disease• HIV infection related facial nerve palsy• Herpes Zoster (Ramsay Hunt Syndrome )

Ramsay Hunt syndrome Herpes zoster virus infection of the geniculate ganglion of the facial nerve.

It is caused by reactivation of herpes zoster virus that has previously caused chickenpox in the patient. The virus infects the facial nerve that normally innervates controls the muscles of the face , causing paralysis.

Ramsay Hunt syndrome is typically associated with red rash and blisters (inflamed vesicles or tiny water-filled sacks in the skin) in or around the ear and eardrum and sometimes on the roof of the mouth or tongue.

How does Ramsay Hunt syndrome compare with Bell's palsy?

Bell's palsy also is a result of injury to the facial nerve by virus infection

There is no red rash associated with Bell's palsy as there is with Ramsay Hunt syndrome

Ramsay Hunt syndrome is caused by the Varicella virus (herpes zoster) that also causes chickenpox.

. Ramsay Hunt syndrome is commonly more painful

than Bell's palsy.

Both can cause eyelid and mouth paralysis on one side of the face

The classic symptom that clinically distinguishes Ramsay Hunt

syndrome is a red painful rash associated with blisters in the ears and facial paralysis on one side of

the face.

The hallmark of leprosy is invasion and inflammation of nerves which are present in all stages of different varieties of the disease. Although leprosy usually affects the superficial nerves, yet any nerve in the body including the cranial nerves can be affected.The 5th and 7th nerves were most frequently affected

Department of Dermatology, Venereology & Leprology, Govt. Medical College Jammu. Jammu & Kashmir, India.

LEPROSY

Idiopathic Facial Paralysis (Bell’s Palsy)Criteria:

Unilateral

Peripheral

Acute onset

No apparent cause

Does not involve any other cranial nerves

Hyperacusis (paralysis of the stapedius muscle)

Otalgia (irritation of the sensory fibers)

Gustatory disturbances

Disturbances of lacrimation

Facial muscles paresis or paralysis

(Motor paralysis is the most important and by far the most common symptom of facial nerve pathology.)

Dryness, crocodile tears : gustatory lacrimation due to faulty neural regulation)

BELLS PHENOMENON “ THE UPWARD

DIVERSION OF THE EYE BALL ON

ATTEMPTED CLOSURE OF THE LID IS SEEN

WHEN EYE CLOSURE IS INCOMPLETE ”

Course and prognosis

Partial paralysis always resolves completely within a few weeks.

Recovery from complete paralysis takes longer (months) and is complete in only about 60-70% of cases.

Approximately 15% of patients are left with troublesome residual palsy and or synkinesis.

Synkinesis

Involuntary associated movement of mimetic muscles accompanying the voluntary movement of other muscles.

An unintended movement of the oral commissure induced by closing the eyes.

This type of synkinesis generally persists as a residual defect following the complete degeneration of nerve fibers

Incomplete eyelid closure due to idiopathic facial paralysis .

• CONTD**

• This occurs when the regenerating nerve fibers do not grow back into the proper muscles.

• The synkinetic movements are almost always present on the involved side.

• Because of the contractures, the face at rest may be more deeply etched on the side of the previous palsy. This can give a false impression of weakness on the opposite side.

The most common symptoms of facial synkinesis include:

• Eye closure with volitional contraction of mouth muscles.

• Midfacial movements with volitional eye closure.

• Neck tightness (Platysmal contraction) with smiling.

• Hyperlacrimation(also called Crocodile Tears).

• A case where eating provokes excessive lacrimation. This has been attributed to neural interaction between the salivary glands and the lacrimal glands.

Laboratory evaluation Patients with facial paralysis should undergo

laboratory undergo laboratory tests to screen for infectious diseases (borreliosis, herpes zoster, syphilis, human immunodeficiency virus [HIV], mononucleosis, toxoplasmosis).

Audiometric testing (pure-tone, speech and immittance measurements) is necessary due to stapedius muscle involvement and the close proximity of cranial nerve VIII.

Others:

Schirmer’s test

(A 30% reduction in lacrimal secretion relative to the opposite side is considered abnormal.)

Stapedial reflex test

Gustometry

(A right-left discrepancy means that the lesion is proximal to the mastoid segment.)

Sialometry

Electroneurography (ENoG): More than 90% degeneration of the nerve fibers is a poor

prognostic sign in terms of complete recovery.

Electromyography (EMG): EMG is also used for the intraoperative monitoring of facial nerve

function during parotid and otologic surgery and intracranial operation.

Magnetic stimulation: If the nerve is responsive to stimulation when facial paralysis

is present, there is a good prognosis for recovery. If the nerve is unresponsive, a prognostic assessmen cannot be made.

Prognosis

The less complete and more acute the paralysis and the earlier treatment is initiated, the better the prognosis.

Traumatic Facial Paralysis

Traumatic rupture

Stretch injury

Nerve compression (by hematoma or bone fragments)

Trauma-induced swelling

Thermal injury (from a drill

Treatment

Every case of immediate paralysis should be surgically explored.

Delayed paralysis is treated initially with corticosteroids to reduce edema. If more than 90 % degeneration or if CT indicates compression by bone fragments, the nerve is surgically explored.

This is also done if other indications for temporal bone surgery exist (cerebrospinal fluid leak, ossicular chain disruption). It is usually sufficient to decompress the nerve.

Bilateral conditions

• Melkersson Rosenthal syndrome• Möbius syndrome• Guillain Barré syndrome• Leprosy• HIV infection related facial nerve :

may precede seroconversion

MELKERSON ROSENTHAL SYNDROME

Rare neurological disorder

Characterized by recurring facial paralysis,

Swelling of the face and lips (usually the upper lip), and development of folds and furrows in the tongue. Onset is in childhood or early adolescence.

Recurrent attacks (ranging from days to years in between), swelling may persist and increase, eventually becoming permanent

Rare congential condition characterised by the absence or under-development of the abducens nerve (CN VI) and facial nerve (CN VII) nuclei.

Clinical presentationThe earliest sign is the inability of the newborn to suckle, with an expressionless face, floppy limbs and drooling.

Pathology• Aetiology is multi-factorial.• Transient ischaemic or hypoxic insult to the fetus.• Infectious and genetic aetiologies have also been proposed.• Additional brainstem involvement is also common • May include other cranial nerves as well as the musculoskeletal system.

 First described by Paul Julius Möbius (1853 - 1907)

Möbius syndrome 

Guillain–Barré syndrome (GBS) 

Defined as heterogeneous group of autoimmune disorders, involving sensory, motor and autonomic nerves and is the most common cause of rapidly progressive flaccid paralysisMost cases preceded by upper respiratory tract infections or diarrhoea 1-3 weeks before its onset, most commonly caused by Campylobacter jejuni 

Clinical presentationClassical presentation includes symmetrical ascending muscle paresis or palsy, areflexia or hyporeflexia along with variable degree of sensory or autonomic involvement.

.

Clinical presentation• Symmetrical ascending muscle paresis or palsy,• Areflexia or hyporeflexia • Variable degree of sensory or autonomic involvement.

Lyme disease • Bacterial infection transmitted by a tick. • First recognized in 1975, • Large numbers of children were being diagnosed with juvenile rheumatoid arthritis in Lyme, Conn., and two neighboring towns.

Also affect The nervous system, causing symptoms such as stiff neck and severe headache (meningitis), temporary paralysis of facial muscles (Bell's palsy), numbness, pain or weakness in the limbs, or poor coordination. More subtle changes such as memory loss, difficulty with concentration, and a change in mood or sleeping habits have also been associated with Lyme disease

A total return to normal function.

• The most common cranial neuropathy seen was the benign seventh cranial nerve palsy (Bell's palsy)• The cases of Bell's palsy were found to occur early in the HIV disease and often during initial seroconversion. • Clinically they were indistinguishable from the classic Bell's palsy.• The CD4+ cell count of affected patients ranged from 356 to 511 cells/mcL, with a mean of 457 cells/mcL.• CSF examinations as well as neuroimaging in all of these cases were normal. • The disease was self-limited, with most of the patients (85%) showing complete recovery within 2 weeks without any therapy. • Only 1 patient who had presented with a low CD4+ cell count had partial recovery of his facial weakness.

Journal of Neurology, Neurosurgery, and Psychiatry 1988;51:425-426

HIV AND BELLS PALSY

Nonopportunistic Neurologic Manifestations of the Human Immunodeficiency Virus: An Indian StudyAlaka K. Deshpande, MD, Mrinal M. Patnaik, MD

Neoplasm(s) and masses

Facial nerve schwannomaFacial nerve haemangiomaFacial nerve choristoma

CNS lesions

Perineural spread especially from head and neck SCC  Adenoid cystic carcinoma of the parotid gland

Trauma : especially temporal bone fractures Cardiofacial syndrome : typically lower lip or complete facial palsy Familial facial palsy

SCALE FOR FACIAL PARALYSIS

The spectrum of facial motor dysfunction is wide, and characterizing the degree of paralysis can be difficult.

• Several systems have been proposed, but since the mid-1980s, the House-Brackmann system has been widely used.

• In this scale, grade I is assigned to normal function, and grade VI represents complete paralysis. Intermediate grades vary according to function at rest and with effort.

 

FACIAL REANIMATION

 Numerous reanimation techniques are available to restore function and are based on the cause of the facial paralysis, type of injury and its location, and the anticipated durationClassified into 4 types as follows: (1)Neural methods, (2) Musculofascial transpositions, (3) Facial plastic procedures, (4) Prosthetics.

The procedures for total unilateral facial paralysis are as follows• Direct facial nerve anastomosis• Interpositional grafts• Anastomosis to other motor nerves• Dynamic musculofascial transpositions• Static musculofascial transpositions• Facial plastic procedures

• Attempts to correct facial paralysis date back to 200 AD, when Galen actually discussed the possibility of nerve regeneration. • The first documented suture repair of a nerve is attributed to Paul of Argina in 600 AD. • A.Waller, who recognized that peripheral nerves could regenerate, rediscovered this work in the 1850s.

“As early as the turn of the century, Alexer in Eden recognized the transposition of muscles in lieu of primary nerve anastomosis.

Reuben, Baker, and Connelly repopularized this intervention in the late 1970s by using either the temporalis or masseter muscle”.

.

Technique cannot be used if the donor nerve is essential to the overall function of the patient.

Reinnervation proceduresHypoglossal–Facial Transfer (XII-VII Crossover)

• The nerve most often utilized to reinnervate the distal facialnerve .

• Its proximity to the extratemporal facial nerve,

• Dense population of myelinated motor axons,

• The relative acceptability of the resultant hemitongue weakness, and

• The highly predictable and reliable resultmake it a logical choice

REINNERVATION TECHNIQUESReinnervation techniques, also termed nerve substitutiontechniques, are procedures that provide neural input to thedistal facial nerve and facial musculature via motor nerves

SURAL NERVE

MUSCLE TRANSPOSITIONTemporalis Muscle TranspositionWhen intact, the temporalis muscle is the first choice for reanimation of the smile in the chronically paralyzed face

Other Regional Muscle Transfers

• The masseter muscle transfer, popularized by Rubin and by Baker and Conley , can also provide excursion atthe oral commissure.

• The digastric muscle transfer is useful in isolated marginal mandibular nerve injuries, but compromises oral competence in the total facial paralysis patien

STATIC FACIAL REANIMATION PROCEDURESPatients who are poor candidates for prolonged general anesthesia for medical reasons,

patients with a poor prognosis in whom reanimation over a long time is not appropriate, and dynamic reanimation failures.

Patients with partial recovery following Bell’s palsy,

Ramsay Hunt syndrome, or other conditions leading to aberrant regeneratioN

• If oral incompetence is a significant complaint, lateral lower lipresection or selective myomectomy may be of benefit; • Fascia lata slings have been described to improve cosmesis and competence in this area • Creation of a nasolabial fold via a two-stitch prolene suture technique, a modification of the Keller facelift .has proven effective for management options for the eye

PROSTHESIS FOR FACIAL REANIMATION

Indications

If the duration of the paralysis is less than 24 months and no chance of recovery

exists, attempt a neural procedure. If the motor end plates are not viable, or immediate

restoration of some movement is desirable, a muscle transposition technique may be

used.

ContraindicationsNo contraindications exist for restoring facial reanimation in a patient, except

inability to tolerate general anesthesia; however, specific guidelines must be

followed. If the possibility of spontaneous facial nerve recovery exists, then any

procedure that involves transsection of the nerve must be avoided until lack of

recovery is a certainty.

ProblemTotal disruption of the facial nerve does not permit restoration to complete normalcy.

Therefore, realistic expectations must be established at the initial encounter and

candidly discussed between the physician and the patient

“Surgical Importance”

The preauricular approach Used to access and treat fractures in the mandibular condylar head and neck region. Many surgeons perform temporal mandibular joint (TMJ) surgery

Branches of the facial nerve may be involved in this incision and dissection.

PRE-AURICULARINCISION

Incision A modified Blair incision is used . The preauricular incision is made in the preauricular crease. The skin flap is raised to the superior, anterior and inferior borders of the glandStensen’s Duct• Is used as a landmark for the identification of the buccal branches of the facial nerve. • The facial nerve lies across the duct in most cases, and the duct should be preserved during the dissection of the nerve; the duct, however, is ligated and cut if the facial nerve is below the duct.The retromandibular vein is used as a landmark for the identification of the marginal mandibular branch, and the zygomatic arch for the zygomatic branch of the facial nerve.

• Use of a local anesthetic with vasoconstrictor may impair the function of the facial nerve and impede the use of a nerve stimulator during the surgical procedure. • Using a physiological solution with vasoconstrictor alone or injecting the local anesthetic with vasoconstrictor very superficially.

Make an oblique incision parallel to the frontal branch of the facial nerve, through the superficial layer of the temporalis fascia above the zygomatic arch.The frontal branch of the facial nerve is protected within the superficial layer of the deep temporalis fascia.

Incising temporalis fascia The temporalis fascia is a glistening white tissue layer that is best appreciated in the superior portion of the incision.

The main neural structure is the marginal mandibular branch of the facial nerve (CN VII). The facial artery and vein are also encountered during this dissection.

 Skin incision 2-3 cm below the inferior border of the mandible.

Superior subplatysmal dissection exposes the underlying marginal mandibular branch of the facial nerve (CN VII).By ligating and dividing the facial artery and vein and then retracting the vessels superiorly, the marginal mandibular branch of the facial nerve remains included in the superior flap and is thus protected.

Incision of skin and subcutaneous tissues exposes the underlying platysma muscle.

The incision can either be parallel to the inferior border of the mandible or be placed in an existing skin crease for maximum cosmetic benefit.

SUBMANDIBULAR INCISION

Several points should be emphasised to avoid mechanical damage to the facial nerve:

Dissection of the facial nerve should be done just above the nerve to show it clearly. To dissect below the nerve is inadvisable. The sheath of the facial nerve should not be opened to avoid damage to the nerve fibres.

The dissected nerve should be covered by wet gauze to avoid exposure to the air.

Bleeding from capillary vessels should be stopped by the pressure of wet gauze, as some blood vessels are distributed along with the nerve. The facial nerve is readily damaged if artery forceps are used for haemostasis. The dissection may be continued in the other areas of the gland whilst attaining this haemostasis.

The bifurcation of the nerve is close to the retromandibular vein, and any fine branches of the vein should be ligated and carefully sectioned.

The branching ducts of the gland must be distinguished from the facial nerve. In general, the nerve is white and shiny, while the duct is grey and dull.

Relationship among (1) the buccal branch of the facial nerve, (2) the accessory gland and (3)

parotid duct

Kaban, Perrott and Fisher It was noted that facial nerve injury occurred in 75% of the cases of osseous ankylosis and in 25% of those of fibro-osseous ankylosis, The degree of surgical difficulty was an important factor in the appearance of facial nerve lesion.Al-Kayat and Bramley • Carried out a cadaveric study of the relationship of the facial nerve and its branches with the region of the TMJ. • The zygomatic branch of the facial nerve crosses the region of the zygomatic arch at a distance of 2.0 ± 0.5 cm from the anterior wall of the external auditory canal.• The bifurcation of the main trunk of the facial nerve occurs 3.0 ± 0.31 cm from the postglenoidal tubercule and at a mean distance of 2.3 ± 0.28 cm from the inferior concavity of the external acoustic meatus.

TMJ SURGERY

AND FACIAL NERVE

Roychoudhury, Parkash and Trikha • On using the the measurements of the study conducted by Al-Kayat and Bramley as a parameter in their operations, they achieved a decrease in the number of facial nerve injuries in a series of surgical approaches for the treatment of temporomandibular ankylosis. • It was observed that 22% of the surgical approaches resulted in facial nerve injury

.

Facial nerve palsy, as a complication of an inferior alveolar nerve block

anesthesia.

• Is a rarely reported incident.• Based on the time elapsed, from the moment of the injection to . the onset of the symptoms, the paralysis could be either * Immediate

* Delayed

 

In the immediate type, the paralysis occurs within minutes of injection with a recovery period of

3 hours or less

. However, in the delayed type the symptoms appear within

several hours to several days, while recovery may expand from

24 hours to several months

The immediate type • The direct accidental anesthesia of one or more branches of the facial nerve•  This is possible when an injection is administered too far posteriorly, the anesthetic solution could be injected into the parotid substance

PATHOGENESIS

A sympathetic vascular reflex, leading to ischemic paralysis in the stylomastoid foramen region.

The anesthetic solution, its breakdown products, or even the mechanical action of the needle itself, may lead to stimulation of the sympathetic plexus associated with the external carotid artery, which in turn communicates with the plexus covering the stylomastoid artery as it enters the parotid gland.

The trauma involved in the procedure of dental anesthesia.

• Acts as a releasing factor, reactivating a latent viral infection such as herpes simplex virus (HSV) or varicella-zoster virus (VZV). The above could be responsible for neural sheath inflammation and consequent facial nerve palsy

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