facial nerve.pptx

8/10/2019 FACIAL NERVE.pptx

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F CI L NERVE

Moderator: Presenter:Dr k ranganath Dr prashanth l

P G Trainee



CONTENTS

Introduction

Embryology

Origin

Functional components

Course and relations

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Communications

Branches

Vascular supply

Facial nerve paralysis

References

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introduction

The facial nerve is the seventh (VII) of twelve

paired cranial nerves.

It is the nerve of facial expression.

The facial nerve is composed of approximately

10,000 neurons, 7,000 of which are myelinated

and innervate the nerves of facial expression and

3000 of the nerve fibres' are somatosensory and

secretomotor and make up the nervus intermedius

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EMBRYOLOGY OF F CI L NERVE

Tissue which will become the facial nerve is first

identifiable at the end of 3 rd week of gestation

when the entire embryo is 3mm long.

At this stage, a collection of neural crestal cells

appears dorsolateral to rhombencephalon and just

rostral to otic (acoustic) placode.

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These cell collection also gives rise to 8 th (acoustic)

cranial nerve, therefore it is called as“fascioacoustic (or acousticofacial ) primordium

or crest” .

By the end of 4 th week , the facial and acousticportions of primordium become more distinct.

The facial portion of the primordium is a narrow

cell column which extends to a thickened area ofsurface ectoderm called a placode .

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This placode is located on the surface of upper

portion of second pharyngeal arch.

During early 5 th week, the geniculate ganglion

begins as a collection of neuroblasts in the facial

portion of primordium.

Proximal segment of primordium becomes less

cellular and more fibrous in appearance.

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Distal segment is ill-defined but separates intotwo almost equal branches:

i. one courses caudally into dense mesenchyme of

second pharyngeal arch and represents futuremain trunk of facial nerve.

ii. the other curves down to the first arch to

become the chorda tympani nerve.

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origin of facial nerve

DEEP/NUCLEAR ORIGIN :

1. Facial/motor nucleus

2. Superior salivatory

nucleus

3. Upper part of nucleus of

tractus solitarius

4. Upper part of the spinal

nucleus of trigeminal nerve

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1. Facial/Motor NucleusIt lies deep in the reticular formation

of lower pons, below and in front of

abducent nucleus.

It represents special visceral efferent

column which supplies muscles of

face.

At the cranial end of abducent

nucleus , the fibres bend abruptly

downwards and forwards forming an

internal genu and emerge at the

lower border of the pons through the

motor root.

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2. Superior Salivatory Nucleus

It is situated dorso lateralto the caudal part of motor

nucleus.

It represents general

visceral efferent column.

Gives origin to the

preganglionic secretomotor

fibres which emerge

through the sensory root.

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3. Nucleus Of Tractus

Solitarius

It represents special visceral

afferent and possibly general

visceral afferent column.

It receives taste sensation

from anterior 2/3 rd of tongue

via chorda tympani nerve,

and from soft palate through

greater petrosal nerve.

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4. Spinal Nucleus Of Trigeminal Nerve

Possibly it receives

cutaneous sensations from

auricle through auricular br

of vagus, and cell bodies of

these fibres are located in

geniculate ganglion of facial

nerve.

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SUPERFICIAL ORIGIN :

The facial nerve consists of a

motor and a sensory part(nervus intermedius)

The two parts emerge at the

lower border of the pons in the

recess between the olive and the

inferior peduncle, the motor part

being the more medial,

immediately to the lateral side ofthe sensory part is the acoustic

nerve.

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Functional components of facialnerve

1. Branchiomotor- motor fibres:

supply the muscles which are

derived from second arch.

2. Preganglionic secretomotor fibres:

for submandibular ,sublingual,lacrimal glands and glands of soft

palate and nasal cavity.

3. Special sensory fibres: from

anterior 2/3 rd of tongue and soft

palate.

4. General sensory fibres: from

concha of auricle.

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Course and relations

Course of the facial nerve

may be divided by

stylomastoid foramen

into

Intracranial part

Extracranial part

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Intracranial part: The facial nerve emerges from the brainstem with the

nerve of Wrisberg, i.e. the nervus intermedius.

The nervus intermedius gained its name from its

position as it courses across the cerebellopontine angle

(CPA) between the facial nerve and thevestibulocochlear nerves.

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The average distance between

the point where the nerves exitthe brainstem and the place

where they enter into the

internal auditory canal (IAC) is

approximately 15.8 mm.

The facial nerve and the nervus

intermedius lie above and

slightly anterior to CN VIII.

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At the fundus of the

meatus, the two roots,

sensory and motor roots

fuse to form a single trunk,

which lies in the petrous

temporal bone.

Within the canal, course of

the nerve can be divided

into three parts by two

bends.

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First part, is directed laterally

above the vestibule.

Second part, runs backwards

along the medial wall of the

middle ear, above the

promontory.

Third part, is directed vertically

downwards behind the

promontory.

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First bend, at the junction of first and second parts is

sharp. it lies over the anterosuperior part of the

promontory, and is called as genu .

The geniculate ganglion of the nerve is so called

because it lies on the genu.

Second bend is gradual and lies b/w promontory and

aditus to the mastoid antrum.

Finally the nerve passes vertically downwards along the

posterior wall of the tympanic cavity and leaves the

temporal bone through the stylomastoid foramen.

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Extracranial part:At its exit from the foramen the

facial nerve changes the

direction, passes forward

superficial to the styloid process

of temporal bone and pierces the

posteromedial surface of parotid

gland.

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Within the gland the nerve runs forward for about 1cm

superficial to the retromandibular vein and external

carotid artery, and then divides into: temporo-facial

trunk and cervico-facial trunk.

Temporo-facial trunk turns abruptly upwards and

subdivides into temporal and zygomatic branches.

Cervico-facial trunk passes downwards and forward &

subdivides into buccal , marginal mandibular and

cervical branches.

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The five terminal branches radiate like the goose’s foot

through the anterior border of the gland and supply the

facial muscles. Such patterning is called “ pes anserinus”

The trunks branch further to form a parotid plexus (pes

anserinus), which exhibits variations in branching pattern.

They leave the parotid gland by its anteromedial surface,medial to its anterior margin and supply the muscles of

facial expression.

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Communications of the facial nerve

In the internal acoustic meatus:a. communicates with the vestibulocochlear nerve.

At the geniculate ganglion:

a. communicates with pterygopalatine ganglion through the

greater petrosal nerve.

b. communicates with otic ganglion by a branch which joins

with lesser petrosal nerve.

c. communicates with sympathetic plexus around middle

meningeal artery by a branch called as external petrosal n.

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In the facial canal:

a. With the auricular branch of vagus nerve, through

which facial nerve possibly conveys cutaneous

sensations from concha.

Below the stylomastoid foramen:

a. With glossopharyngeal nerve

b. With vagus nerve

c. With auriculotemporal nerve

d. With greater auricular nerves

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Behind the ear:

a. With lesser petrosal nerve

In the face:

a. With the branches from trigeminal nerve

In the neck:

a. with the transverse cervical cutaneous nerve

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Branches of facial nerve

In the facial canala. Nerve to the stapedius:

it arises from the facial nerve opposite the pyramidal

eminence and supplies the stapedius muscle.

paralysis of this nerve causes hyperacusis.

b. Chorda tympani nerve:

It arises from the facial nerve about 6cm above the

stylomastoid foramen.

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It conveys taste fibers from the anterior 2/3 rd of the

tongue except vallate papillae.

It also gives preganglionic secretomotor fibres for

submandibular and sublingual glands along with

lingual nerve.

Chorda tympani nerve represents pretrematic nerve of

the first branchial arch.

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Below the stylomastoid foramen

Posterior auricular nerve:

It passes upwards and backwards behind the auricle.

Supplies the intrinsic muscle of cranial surface of

auricle , auricularis posterior and occipital belly of

occipito-frontalis.Nerve to the posterior belly of digastric

Supplies posterior belly of digastric muscle.

Nerve to the stylohyoid muscleSometimes these two branches arises as a common

trunk.

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In the face

Temporal branchZygomatic branch

Buccal branch

Marginal mandibularbranch

Cervical branch

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Temporal branch :

Passes upwards in front of auricle and across the

zygomatic arch.

Supplies intrinsic muscle of lateral surface of auricle,

auricularis anterior & superior muscles, upper part of

orbicularis oculi, frontalis and corrugator supercilli.

Zygomatic branch :

runs along the zygomatic arch

Supplies the lower part of orbicularis oculi muscle.

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Buccal branch :

Consists of superficial and deep partsSuperficial branches supply procerus.

Deep branches subdivide into upper and lower sets.

Upper buccal passes forwards above the parotid ductand supplies zygomaticus major and minor, levator

anguli oris, levator labii superioris, levator labii

superioris alaque nasi and muscles of the nose.

Lower buccal passes below the parotid duct and

supplies buccinators and orbicularis oris.

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Marginal mandibular branch :

Appears first in the neck and then curves upwards and

forwards across the lower border of the mandible.

Appears in the face after crossing superficial to the

facial artery and vein.

Supplies risorius, depressor anguli oris, depressor labii

inferioris and mentalis.

Cervical branch :

Appears in anterior triangle of neck.

Supplies the platysma.

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Vascular supply of facial nerve

The cortical motor area of the face is supplied by theRolandic branch of the middle cerebral artery.

Within the pons, the facial nucleus receives its blood

supply primarily from the anterior inferior cerebellarartery (AICA).

The AICA, a branch of the basilar artery, enters the

internal auditory canal (IAC) with the facial nerve.

The AICA branches into the labyrinthine and cochlear

arteries.

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The superficial petrosal branch of

the middle meningeal artery is the

second of 3 sources of arterial

blood supply to the intrapetrosal

facial nerve.

The posterior auricular artery

supplies the facial nerve at and

distal to the stylomastoid foramen.Venous drainage parallels the

arterial blood supply.

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facial nerve paralysis

Facial nerve paralysis may be:

1. Supranuclear paralysis2. Nuclear paralysis

3. Infranuclear paralysis

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Supranuclear Facial ParalysisSupranuclear facial paralysis involving “upper motor

neuron” pathways is usually a part of hemiplegia

caused by the occlusion of a blood vessel supplying

the internal capsule or motor cortex.

This results in impairment or loss of movements oflower facial muscles of the contra lateral side, but the

upper facial muscles are escaped.

This is due to bilateral control of motor cortex to the

subgroups of motor nuclei which supply the upperfacial muscles.

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Voluntary movements are of lower

part of the face are more affected

than emotional movements due tointerruption of cortico-bulbar and

cortico-reticular fibres.

Occasionally supranuclear lesions

may abolish or weaken emotional

movements but not voluntary

movements.

Electrical reaction of affectedmuscles are unaltered.

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Nuclear Facial Paralysis

A lesion in the pons may involve motor nucleus of the facial

nerve along with abducent nucleus around which motor root

makes a loop.

This results in lower motor neuron paralysis producing loss

of movements of all facial muscles on the affected side

associated with internal strabismus due to involvement of

lateral rectus muscle of the eyeball.

Sometimes a pontine lesion affects the pyramidal tract and

the facial nucleus and is expressed as millard gublarsyndrome which is characterized by contra lateral

hemiplegia and ipsilateral facial palsy.

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Infranuclear Facial Paralysis

A lesion interrupting the peripheral

part of the facial nerve is known as

bell’s palsy .

Bell’s palsy when complete,

produces lower motor neuronparalysis of all facial muscles on the

affected side with abolition of both

voluntary and reflex movements.

The manifestations of peripheral

injury vary according to the site of

involvement.01-11-2014 08:16 41



Lesion in the internal acoustic meatus produces bell’s

palsy and deafness due to involvement of the

vestibulocochlear nerve.Lesion at the genu, produces:

a. Diminished lacrimation.

b.Diminished submandibular secretion.

c. Reduced taste sensation on the anterior 2/3 rd of the

tongue.

d. Hyperacusis due to involvement of nerve to the

stapedius.

e. Along with the signs of bell’s palsy on the affected

side.01-11-2014 08:16 42



During the recovery from an injury proximal to the

genicular ganglion, some regenerating salivary fibres

may pass through greater petrosal nerve and reach

pterygopalatine ganglion.

This is manifested by paroxysmal lacrimation during

eating and is known as crocodile tears syndrome .

A lesion of the facial nerve between the genu and

pyramidal eminence produces:

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a. Diminished submandibular secretion.

b. Hyperacusis due to involvement of nerve to the

stapedius.

c. Along with the signs of bell’s palsy on the

affected side.

An injury to the facial nerve below the

stylomastoid foramen produces bell’s palsy

without affecting other functions.

In typical facial paralysis, following

manifestations are observed on the affected side.

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Transverse wrinkles of the forehead

disappear and the eye brow droops.

Palpebral fissure is wider than normal

side due to unopposed action of

levator palpebrae superioris.

Patient is unable to close his eyelids

and the tears roll over the cheek.

Corneal reflex is disturbed which may

culminate into corneal ulcers and

blindness.

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When an attempt is made to close the

eyelids, the eye ball on the affected side may

be seen to roll upward, this is known asbell’s phenomenon .

Nasolabial fold disappears, ala does not

move and the tip of the nose is deviated to

the unaffected side.

During smiling the angle of the mouth

remains motionless on the affected, where as

the other angle moves upwards and laterally. This makes the oral fissure triangular in

shape.

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Due to paralysis of the buccinator, food accumulates in

the vestibule of the mouth and occasionally dribbles

out between the paralyzed lips.

Pursing of the whistle is disturbed and labial speech

may be affected.

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Other causes of facial nerve paralysis:

Trauma

Herpes zoster infection

Otitis media

NeurosarcoidosisMoebius syndrome

Tumors

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Trauma

Physical trauma, especially fractures of the temporalbone, may also cause acute facial nerve paralysis.

Most commonly, facial paralysis follows temporal bone

fractures, though the likelihood depends on the type of

fracture.

Traumatic injuries can be assessed by computed

tomography (CT) and nerve conduction studies (ENoG).

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Herpes zoster infection

Herpes zoster infection that affects cranial nerves VII

(facial nerve) and VIII (vestibulocochlear nerve).

Patients present with facial paralysis, ear

pain, vesicles, sensory neural hearing loss, and vertigo.

Management includes Antiviral drugs and

oral steroids .

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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.

Antibiotics are used to control the otitis media, and

other options include a wide myringotomy (an incision

in the tympanic membrane) or decompression if the

patient does not improve .

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Neurosarcoidosis

Facial nerve paralysis, sometimes bilateral, is acommon manifestation of neurosarcoidosis

(sarcoidosis of the nervous system).

It is a rare condition.

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Moebius syndrome

Moebius syndrome is a bilateral facial paralysis

resulting from the underdevelopment of the VII cranial

nerve (facial nerve), which is present at birth.

The VI cranial nerve, which controls lateral eye

movement, is also affected,

So people with Moebius syndrome cannot form facial

expression or move their eyes from side to side.

Moebius syndrome is extremely rare, and its cause or

causes are not known.

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Tumors

A tumor compressing the facial nerve anywhere along

its complex pathway can result in facial paralysis.

Common culprits are facial neuromas,

congenital cholesteatomas, hemangiomas, acoustic

neuromas, parotid gland neoplasms, or metastases of

other tumours.

Patients with facial nerve paralysis resulting from

tumours usually present with a progressive, twitching

paralysis,

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Computed tomography (CT) or magnetic resonance

(MR) imaging should be used to identify the location of

the tumour, and it should be managed accordingly.

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DIFFERENTIAL DIAGNOSIS OF FACIALNERVE PARALYSIS

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Grade Descriptions Characteristics

I Normal Normal facial function in all areas

II Mild dysfunction Slight weakness noticeable on closeinspection; may have very slight synkinesis

III Moderate

dysfunction

Obvious, but not disfiguring, difference

between 2 sides; noticeable, but not severe,synkinesis, contracture, or hemifacial spasm;complete eye closure with effort

IV Moderatelyseveredysfunction

Obvious weakness or disfiguring asymmetry;normal symmetry and tone at rest; incompleteeye closure

V Severedysfunction

Only barely perceptible motion; asymmetry atrest

VI Total paralysis No movement

House-Brackmann Facial Nerve Grading System



Treatment of facial paralysis

SteroidsCorticosteroid such as prednisone significantly

improves recovery at 6 months and are thus

recommended.Early treatment (within 3 days after the onset) is

necessary for benefit with a 14% greater probability of

recovery.

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Antivirals

Antivirals (such as acyclovir) are ineffective in

improving recovery from Bell's palsy beyond steroids

alone.

They were however commonly prescribed due to a

theoretical link between Bell's palsy and the herpes

simplex and varicella zoster virus.

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Physiotherapy

Physiotherapy can be beneficial to some individuals

with Bell’s palsy as it helps to maintain muscle tone ofthe affected facial muscles and stimulate the facial n.

It is important that muscle re-education exercises

& soft tissue techniques be implemented prior torecovery in order to help prevent

permanent contractures of the paralyzed facial

muscles. To reduce pain, heat can be applied to the affected side

of the face.

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Surgery

Surgery may be able to improve outcomes in facial nerve

palsy that has not recovered.

A number of different techniques exist.

Smile surgery or smile reconstruction is a surgical procedure

that may restore the smile for people with facial nerve

paralysis.

It is unknown if early surgery is beneficial or harmful.

Adverse effects include hearing loss which occurs in 3-15%

of people.As of 2007 the American Academy of Neurology did not

recommend surgical decompression.

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Complementary therapy

The efficacy of acupuncture remains unknown becausethe available studies are of low quality (poor primary

study design or inadequate reporting practices)

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references

1. Facial nerve, schaitkin barry, may mark.

2. Gray’s anatomy, 39 th edition.

3. Essentials of human anatomy [ head and neck]- A K

Datta , 3 rd edition.

4. Human anatomy- B D Chaurasia 4 th edition.

5. Internet

01-11-2014 08:16 64

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