Facial Nerve

FACIAL NERVE

Introduction

Functional components

Branches

Introduction to Facial Nerve

• seventh (VII) of twelve paired cranial nerves.• emerges from the brainstem between the pons and

the medulla• controls the muscles of facial expression, and functions in the

conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity.

• also supplies pre-ganglionic parasympathetic fibers to several head and neck ganglia.

• nerve of the second branchial arch

FUNCTIONAL COMPONENTS OF FACIAL NERVE

Brief overview of cranial nerve functional components

• The 12 cranial nerves participate in a total of seven neural functions. Each of these seven functions is designated by a three letter acronym.

• The first letter is either G (General) or S (Special).– General refers to primitive and/or external structures of the body.– Special refers to senses unique to the head (taste, olfaction, hearing, vision, and

balance) and to muscles of branchial arch derivatives.• The second letter is either S (Somatic) or V (Visceral).

– Somatic refers to non-visceral structures including skin, muscles, tendons, joints, retina (vision), basilar membrane (hearing), and utricle/saccula (balance).

– Visceral refers to organs of the body cavity, smooth muscle, vessels, and glands.• The third letter is either A (Afferent) or E (Efferent).

– Afferent refers to flow of neural information toward the brain (sensation)– Efferent refers to flow of neural information toward the periphery (motor).

• Knowledge of the functional components and the deficits that follow damage to each provides the basis of the thorough neurological exam.

The Seven Functional Components• GSA – General Somatic Afferent

– Touch, temperature, and pain from non-visceral structures• GSE – General Somatic Efferent

– Motor to skeletal muscle• GVA – General Visceral Afferent

– Touch (distention), temperature, and pain from the viscera• GVE – General Visceral Efferent

– Motor to viscera, smooth muscle, and glands• SSA – Special Somatic Afferent

– Vision, hearing, and balance• SSE – Doesn’t exist• SVA – Special Visceral Afferent

– Taste and olfaction• SVE – Special Visceral Efferent

– Motor to muscles derived from the branchial arches

Facial nerve nuclei

1. Special visceral or branchial efferent: to muscles of facial expression and elevation of hyoid bone.

2. General visceral efferent or parasympathetic: secretomotor to the submandibular and sublingual salivary glands, the lacrimal glands and glans of nose, the palate and the pharynx.

3. General visceral afferent component: carries afferent impulses from the above mentioned glands.

4. Special visceral afferent : carries taste sensation from the palate and from the anterior two thirds of the tongue except the vallate papillae.

5. General somatic afferent: Sensory from somatic touch, temperature, and pain.

Origin and course• The facial nerve consists of a motor and a sensory part,

the latter being frequently described under the name of the nervus intermedius (pars intermedii of Wrisberg).

• The two parts emerge at the lateral part of the lower border of the pons in the recess between the olive and the inferior peduncle, just medial to the eighth cranial nerve.

• The two nerves, with the motor nerve being medial run laterally and forwards, with the eighth nerve to reach the internal acoustic meatus.

Overview of Facial Nerve anatomy in the skull

Lacerate foramen

Facial canal

Internal AcousticMeatus

StylomastoidForamen

Hiatus of canal of greater superficial petrosal nerve

Pterygoid canalGreater superficialPetrosal nerve (GSPN)

Petrotympanicfissure

Greater andlesser palatinecanals

Chorda tympani nerve

Facial nerve

Facial nerve

PosteriorCranialFossa (PCF)

Inferior Orbital Fissure

The facial nerve exits the posterior cranial fossa (PCF) at the internal acoustic meatus.

Click here to start Animation

Posteriorauricular N.

• In the meatusThe motor nerve lies in a groove

on the eighth nerve, with the sensory nerve intervening

Here, the seventh and the eighth nerve are accompanied by the labyrinthine vessels

At the bottom or fundus of the meatus, the two roots, sensory and motor, fuse to form a single trunk, which lies in the petrous temporal bone.

• Within the facial canal:The course can be divided into three parts by two

bendsParts:The first part is directed laterally above the

vestibule.The second part runs backwards in relation to the

medial wall of the middle ear, above the promontory.

The third part is directed vertically downwards behind the promontory.

Course of facial nerve in facial canal(intracranial)

• Bends:• The first bend at the junction of the first and

second parts is sharp. It lies over the anterosuperior part of the promontory, and is also called the genu, and so the name geniculate ganglion of the nerve as it lies on the genu.

• The second bend is gradual, and lies between the promontory and the aditus to the mastoid antrum.

• The facial nerve leaves the skull by passing through the stylomastoid foramen.

• Extracranial courseThe facial nerve crosses the lateral side of the base of the

styloid process

Enters the posteromedial surface of the parotid gland

Runs forwards through the gland crossing the retromandibular vein and the external carotid artery

Behind the neck of the mandible, it divides into its five terminal branches which emerge along the anterior border of the parotid gland


Lacerate foramen

Facial canal


StylomastoidForamen





Chorda tympani

Facial nerve

Facial nerve

PosteriorCranialFossa



The descending portion of the facial nerve exits the facial canal at the stylomastoid foramen and continues into the parotid region

ParotidregionPosterior

auricular N.

Nuclei of the Facial Nerve

• Motor nucleus of facial nerve• Superior salivatory nucleus• Nucleus of tractus solitarius• Lacrimatory nucleus

Facial motor nucleus• Situated in the caudal portion of the ventrolateral pontine tegmentum.• Its axons take an unusual course, traveling dorsally and looping around the abducens

nucleus, then traveling ventrally to exit the ventral pons medial to the spinal trigeminal nucleus. These axons form the motor component of the facial nerve, with parasympathetic and sensory components forming the nervus intermedius.

• The part of the nucleus that supplies muscles of upper part of face receives corticonuclear fibres from the motor cortex of both the right and left sides. In contrast, the part of the nucleus that supplies muscles of the lower part of the face receive corticonuclear fibres only from the opposite cerebral hemisphere.

Superior salivatory nucleus• Lies in the lower pons• Sends fibres through the facial nerve and its chorda

tympani branch to the submandibular ganglion for supply of the submandibular and the sublingual salivary glands.

Nucleus of tractus solitarius• The nucleus of the solitary

tract, or NTS (Latin: nucleus tractus solitarii), is located along the length of the medulla oblongata (with a small portion in the lower pons).

• Receive visceral sensation and taste from the facial (VII),glossopharyngeal (IX) and vagus (X) cranial nerves.

http://en.wikipedia.org/wiki/Latin_language

http://en.wikipedia.org/wiki/Taste

Lacrimatory nucleus• Lies near salivatory nucleus(in the lower pons)• Gives off fibres that pass through the facial

nerve and its branch, the greater petrosal nerve to relay in the pterygopalatine ganglion and supply the lacrimal, nasal and palatal glands.

Facial Nerve Branches and Supply

1.Within the facial

canal

•Greater petrosal nerve•The nerve to stapedius•The chorda tympani

2.At its exit from the

stylomastoid foramen

•Posterior auricular•Digastric •Stylohyoid

3.Terminal branches within

the parotid gland

•Temporal•Zygomatic •Buccal•Marginal mandibular•Cervical

4.Communicating branches with

adjacent cranial and spinal nerves

The greater superficial petrosal nerve

• Arises from the geniculate ganglion, and consists chiefly of sensory branches which are distributed to the mucous membrane of the soft palate; but it probably contains a few motor fibers which form the motor root of the sphenopalatine ganglion.

• It passes forward through the hiatus of the facial canal, and runs in a sulcus on the anterior surface of the petrous portion of the temporal bone beneath the semilunar ganglion, to the foramen lacerum and in the foramen is joined by the deep petrosal, from the sympathetic plexus on the internal carotid artery, to form the nerve of the pterygoid canal which passes forward through the pterygoid canal and ends in the sphenopalatine ganglion.


Lacerate foramen


StylomastoidForamen





Chorda tympani

Facial nerve

Facial nerve




The first branch of the facial nerve, the greater superficial petrosal nerve (GSPN) branches from the geniculate ganglion within the genu of the facial canal and enters the middle cranial fossa (MCF) by way of the hiatus of the canal for the GSPN.

Geniculate ganglion

Facial canal

MCF

Action of superficial greater petrosal nerve:1. Sensation of light touch, temperature, and

pain from the soft palate.2. Taste from the hard and soft palate

Sensation of light touch, temperature, and pain from the soft palate.

soft palate

Light touch, temperature,and pain fromthe soft palate

Click here for animation

GVA

Light touch sensation

Temperature sensation

Pain sensation

GSPN

Facial nerve

Soft palate

Taste from the hard and soft palate


Hard palate

CoSweetened coffee

SVA

GSPN branches fromthe facial nerve at thegeniculate ganglion within the genu of thefacial canal

Taste from the hard and soft palate

The nerve to stapedius• Arises opposite the pyramid of the middle ear,

and supplies the stapedius muscle• Action :the muscle dampens excessive

vibrations of the stapes caused by high-pitched sounds.

• In paralysis of the muscle, even normal sounds appear too loud and is known as hyper acusis.

Lacerate foramen

Facial canal


StylomastoidForamen




Chorda tympani

Facial nerve

Facial nerve




The second branch of the facial nerve, the stapedial nerve, branches from the descending portion of the facial nerve and enters the middle ear.

Stapedial N. Petrotympanicfissure


\Stapedius muscle dampens movement of the ossicles protecting the inner ear from damage from loud noises


The Stapedius muscle dampens movement of the ossicles

The chorda tympani nerveArises in the vertical part of the facial canal about 6 mm above the stylomastoid foramen

It runs upwards and forwards in a bony canal

Enters the middle ear and runs forwards in close relation to the tympanic membrane

Leaves the middle ear by passing through the petrotympanic fissure

Then passes medial to the spine of the sphenoid and enters the infra-temporal fossa

Here, it joins the lingual nerve through which it is distributed

It carries:1. Preganglionic fibres to the

submandibular ganglion for the supply of the submandibular and sublingual salivary glands

2. Taste fibres from the anterior two-thirds of the tongue except the circumvallate papillae

Lacerate foramen

Facial canal


StylomastoidForamen





Chorda tympani N.

Facial nerve

Facial nerve




The third branch of the facial nerve, the chorda tympani nerve, branches from the descending portion of the facial nerve and enters the middle ear. Within the middle ear the chorda tympani nerve crosses the medial surface of the tympanic membrane. It then passes through the petrotympanic fissure to enter the infratemporal fossa.

Infratemporalfossa

The GVE component of the facial nerve transmits preganglionic fibers to the submandibular ganglion via the chorda tympani nerve. From the submandibular ganglion postganglionic fibers innervate the submandibular and sublingual glands, causing salivation.

Superior salivary nucleus


Submandibularganglion

Submandibulargland

Sublingulalgland

GVE

Chordatympani

SVA component provides taste to the anterior 2/3 of the tongue via the chorda tympani nerve.


Taste from the anterior 2/3 of the tongue

SVA

Chorda tympani

The posterior auricular nerve

• Arises just below the stylomastoid foramen• Ascends between the mastoid process and the

external acoustic meatus• Supplies :– Auricularis posterior– Occipitalis– Intrinsic muscles of back of auricle

The Posterior Auricular nerve innervates the posterior auricular muscle, pulling the pinna posteriorly.


SVE component of posterior auricular nerve

Posterior auricularmuscle pulls the pinna posteriorly

SVE

GSA component provides touch, temperature, and pain sensation from the external acoustic meatus.

Click here to start animation

Cotton swab

Touch, temperature, and pain sensation from part of the external acoustic meatus.

GSA

Posteriorauricularnerve

Digastric branch• Arises close to the posterior auricular branch• Short• Supplies the posterior belly of digastric muscle

Through the stylomastoidforamen

4. The Posterior belly of digastric muscle elevates the hyoid bone


Posterior belly of digastric branch of facial nerveinnervates posterior belly of digastric muscle.

Posterior belly of digastric muscle elevates the hyoid bone

SVEThrough the internalacoustic meatus

Stylohyoid nerve

• Arises with the digastric branch• Long and supplies the stylohyoid muscle

Stylohyoid muscle elevates the hyoid bone.

Through the internalAcoustic meatus

Through the stylomastoidforamen

3. The Stylohyoid muscle elevates the hyoid bone


Stylohyoid branch of facial nerveinnervates stylohyoid muscle

SVE

Temporal branch• Crosses the zygomatic arch andsupply– Auricularis anterior– Auricularis posterior– Intrinsic muscles on the lateral side of the ear– Frontalis– Orbicularis oculi– Corrugator supercilli

Zygomatic branch

• Runs across the zygomatic bone and supplies the orbicularis oculi

• Together with temporal branch of ipsilateral side acts to close the eyelid

The temporal and zygomatic branches of the facial nerve provide SVE nerve fibers that innervate the ipsilateral orbicularis oculi, the muscle responsible for closing the eyelid.


Temporal branch

Zygomatic branch

SVEContraction of orbicularisoculi causes the eyelid to close

Buccal branch• Two in number• The upper buccal branch runs above the parotid

duct and the lower buccal branch below the duct• They supply the muscles in the vicinity esp.

buccinator

The buccal branch of the facial nerve innervates the buccinator muscle, the muscle responsible for holding the cheek against the teeth, thus positioning food for chewing.


Buccal branch offacial nerve innervatesBuccinator muscle.

SVE Contraction of the buccinator musclecauses tensing of the cheek whichhelps position food within the occusal planefor chewing

The zygomatic and buccal branches of the facial nerve innervate the ipsilateral zygomaticus major muscle, the main muscle responsible for smiling.


Zygomatic branch

SVE

Zygomaticus major muscle

Contraction of the zygomaticus major musclecauses smiling

Marginal mandibular branch

• Runs below the angle of mandible deep to platysma

• Crosses the body of mandible and supplies muscles of lower lip and chin

The mandibular and buccal branches of the facial nerve innervate the ipsilateral depressor angularis oris muscle, a muscle responsible for frowning.


Mandibular branch

SVE

Depressorangularis oris

Contraction of thedepressor angularis orismuscle causes frowning

• Mandibular Branch (additional)• Familiarity with the location of the marginal

mandibular nerve is essential when operating in the lower face (Fig. 8.7). If the marginal mandibular nerve is injured during surgery, the resulting paralysis of the muscles that depress the corner of the mouth is quite deforming. Dingman and Grabb (1962) noted in a large cadaver study that, posterior to the facial artery, the marginal mandibular nerve passed above the inferior border of the mandible in 81% of dissections..

• Anterior to the facial artery, all the mandibular nerve branches that innervated the mouth depressors passed above the lower border of the mandible. The only nerve branches that passed below the mandible anterior to the facial artery innervated the platysma and were therefore not of major surgical concern. The nerve was superficial to the posterior facial vein in 98% of the cases and superficial to the anterior facial vein in 100% of the cases.

• The same study showed that the mandibular nerve may have one (21%), two (67%), three (9%), or four (3%) major branches. In 5% of the cases, there was anastomosis between the buccal and mandibular rami

• Baker and Conley (1979) write that, in their clinical experience, the mandibular branch of the facial nerve is usually 1 to 2 cm below the lower border of the mandible and can be as much as 3 or 4 cm below it. The mandibular branch is deep to the platysma muscle and therefore fairly well protected throughout its course along the mandible (Fig. 8.8). As it approaches the mouth, it becomes more superficial and enters the undersurface of the depressor muscles (Fig. 8.9). Liebman et al. (1988) performed serial sections of cadavers and described the depth of the marginal nerve around the mouth (Fig. 8.7).

Cervical branch

• Emerges from the apex of the parotid gland • Runs downwards and forwards in the neck to

supply platysma

E. The cervical branch of the facial nerve innervates the platysma muscle, a muscle partly responsible for depressing the mandible.


Platysma muscle

Cervical branch offacial nerve innervatesPlatysma muscle.

Contraction of platysmaMuscle results in depressionof mandible.

SVE

Stapedius muscle dampens movement of ossicles.

Summary of SVE

Facial canal


StylomastoidForamen


Temporal-orbicularis oculi closes eyelids.Zygomatic-zygomaticus majorpartly responsible for smiling.Buccal-buccinator tenses cheekMandibular-depressor angularis oris responsible for frowning.Cervical- platysma helps lower mandible and tightens skin of neck.

Posterior auricularmuscle responsible forposterior displacementof pinna.

Facial nerve

Facial nerve

Posterior belly of digastricelevates hyoid bone.

Stylohyoid muscleelevates hyoid bone.


Facialnucleus

Communicating branches• For effective coordination between the

movements of the muscles of the first, second and third branchial arches, the motor nerves of the three arches communicate with each other

• Facial nerve also communicates with the sensory nerves distributed over its minor territory

Ganglions associated with facial nerve1. The geniculate ganglion:

-located on the first bend of the facial nerve, in relation to the medial wall of middle ear in the facial canal -a sensory ganglion -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.

Geniculate ganglion

• Contains special sensory neuronal cell bodies for taste, from fibers coming up from the tongue through the chorda tympani and from fibres coming up from the roof of the palate through the greater petrosal nerve.

• Sensory and parasympathetic inputs are carried into the geniculate ganglion via the nervus intermedius.

• Motor fibers are carried via the facial nerve proper.

• The greater petrosal nerve, which carries sensory fibers as well as preganglionic parasympathetic fibers, emerges from the anterior aspect of the ganglion.

2. The submandibular ganglion: – (Submaxillary ganglion in older texts) - part of the human autonomic

nervous system.– One of four parasympathetic ganglia of the head and neck. (others are the

otic ganglion, pterygopalatine ganglion, and ciliary ganglion).– Function: responsible for innervation of two salivary glands:

the submandibular gland and sublingual gland.

•small and fusiform in shape.•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•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.

http://en.wiktionary.org/wiki/fusiform

http://www.ask.com/wiki/Chorda_tympani?qsrc=3044

http://www.ask.com/wiki/Chorda_tympani?qsrc=3044

Clinical aspects of Facial Nerve

• Supra nuclear facial paralysis• Bell’s pasly• Melkerson Rosenthal’s syndrome• Ramsay Hunt syndrome

Documents

Facial Nerve