Anatomy of facial nerve/certified fixed orthodontic courses by Indian dental academy

Anatomy of facial nerve and its
applied aspects
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

Learning Objectives
♦ By the end of the presentation a learner
should be able to describe;
♦ 1. Anatomy of the facial nerve.
♦ 2. Applied aspect of the facial nerve.
♦ 3. Disorders associated with the facial nerve
and their treatment.

♦ Introduction
♦ Embryology
♦ Nucleus
♦ Surface marking
♦ Functional components
♦ Course and relations
♦ Branches and distribution
♦ Ganglia
♦ Arterial Supply & Venous Drainage
♦ Applied Aspects
♦ Disorders

Introduction
♦ Facial nerve -seventh cranial nerve
♦ Nerve of facial expression. (special
visceral( branchial) efferent fibres)
♦ Mixed nerve (sensory and motor)
♦ Sensory root- nervus intermedius
♦ Nerve of the 2nd
branchial arch

Embryology
♦ Facial nerve course, branching pattern, and
anatomical relationships - 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
♦ By the end of the 4th
week, the facial and acoustic
portions are more distinct

♦ Early 5th
week - geniculate ganglion forms
♦ Distal part of primordium separates into 2
branches:1) main trunk of facial nerve and 2)
chorda tympani
♦ Near the end of the 5th
week - facial motor nucleus
is recognizable
♦ 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

Nucleus
♦ Motor nucleus or Branchiomotor
(pons)
♦ Superior salivatory nucleus or
parasympathetic (pons)
♦ Lacrimatory nucleus
(parasympathetic, pons)
♦ Nucleus of the tractus solitarious
(sensory, medulla oblongata)

Surface marking
Facial nerve – marked by a short horizontal line
which joins the following 2 points:
1) A point at the middle of the anterior border of the
mastoid process (the stylomastoid foramen lies
2cm deep to this point)
2) Behind the neck of the mandible : The facial nerve
divides into its 5 branches for the facial muscles.

Functional components
1) Special visceral or Branchial efferent
2) General visceral efferent or Parasympathetic
3) General visceral afferent component
4) Special visceral afferent fibers
5) General somatic efferent fibres
* Branchial motor fibers constitute the largest
portion of the facial nerve.
* The remaining components are bound in a distinct
fascial sheath from the branchial motor fibers.
Collectively these components are referred to as
the nervus intermedius.

Functional component overview of the facial nerve.

Course and relations
♦ Intracranially and
extracranially
Internal acoustic meatus
With VIII th
nerve
Brain (motor & sensory root)
Lateral end of meatus
Facial canal

Above vestibule & medial wall of
epitympanic recess
Medial wall of aditus of mastoid antrum
Stylomatoid foramen
geniculum
Above the promontary
from Stylomatoid foramen

Parotid gland
5 terminal branches
Parotid plexus
Facial musclulature
At stylomastoid foramen nerve is about 2 cm deep to
Middle of anterior border of mastoid process

Branches and distribution
A) Within the facial canal-
1. Greater petrosal nerve
2. Nerve to the stapedius
3. Chorda tympani
B) As it exits from the stylomastoid foramina-
1. Posterior auricular
2. Diagastric
3. Stylohyoid

C) Terminal branches within the parotid gland-
♦ Temporal
♦ Zygomatic
♦ Buccal
♦ Marginal mandibular
♦ Cervical
d) Communicating branches with adjacent cranial and
spinal nerves.

Ganglion
♦ Geniculate ganglion
♦ Submandibular ganglion
♦ Pterygopalatine ganglion

Arterial Supply & Venous Drainage
Supplied by
♦ Intracranially –
anterior inferior cerebral artery
♦ In canal –
 superficial petrosal branch of middle
meningeal artery &
 stylomastoid branch of post. auricular or
occipital arteries.

Extracranially - branches from
 stylomastoid,
 post auricular,
 occipital,
 superficial temporal &
 transverse facial arteries.
Venous drainage – into
the venae comitantes of superficial petrosal
and stylomastoid arteries.

Muscles of the face

Name Origin to insertion Action
Epicranius: Frontalis &
Occipitalis
Cranial aponeurosis to
eyebrows
Raises the eyebrows
Orbicularis oculi Portions of the frontal
and maxilla to the Skin
around eyes
Blinks and closes eyes
Orbicularis oris Skin around mouth Closes and protrudes
lips
Buccinator Mandible/maxilla to
skin around mouth
Flattens cheek against
teeth
Zygomaticus Zygomatic bone to
corner of lips
Raises corner of mouth
Platysma Fascia of chest to
lower border of
mandible
Draws mouth
downward

Applied aspects
Bell’s palsy
(idiopathic facial palsy /peripheral facial palsy for
which no cause can be found)
 The condition is named for Sir Charles Bell, a
Scottish Surgeon in Edinburgh in 1821
 Most common type of facial palsy
 affects adults 20 to 40 years
 Men and women are equally affected
 Characterized by an acute unilateral infranuclear
facial palsy

Triggering event Or Phenomenon related to Bell’s
Palsy
- Acute otitis media
- Atmospheric pressure
change (diving, flying)
- Exposure to cold
- Local and Systemic
infections (viral,
bacterial and fungal)
- Parotitis
- Cysts and tumors
- Dental treatment
- Trauma, temporal
bone fractures,trauma
to the facial nerve
- Surgical wounds

Clinical features
♦ Sudden one sided facial
paralysis
♦ Not able to close the eye
♦ Inability to blink
(resulting in drying, erosion
and ulcer formation on the
cornea)
♦ Tingling, twitching or
numbness of the face.
♦ Forehead doesn’t wrinkle.
♦ Lower part of the face
may droop down.
♦ Inability of the mouth to
smile or fill the cheeks
with air.
♦ Speech is affected.
♦ Pain in the back of the
head, ear or the affected
side of the face.
♦ Nose feels stuffed or
blocked, or runs.
♦ Tooth decay & gingival
diseases

Diagnostic tests:
. Hearing test- Bing test (a vibrating tuning fork is held to
the mastoid process and the auditory meatus is alternately
occluded and left open; an increase and decrease in
loudness is perceived by the normal ear and in
sensorineural hearing loss, whereas the hearing of no
difference occurs in conductive hearing loss.)
. Imaging: CT or MRI
. Electrical test

Bell’s phenomenon
When a patient with peripheral facial
paralysis attempts to close the eye, there is
an upward movement of the eye and the
eyelid on the paralysed side of the face
remains open.
(becomes noticeable only when the orbicularis
muscle becomes weak as in, for example, bilateral
facial palsy associated with the Guillain-Barré
syndrome. )

Treatment
♦ The use of paper tape to depress the upper
eyelid during sleep and prevent corneal
drying,
♦ massage of the weakened muscles.
♦ Glucocorticoids, (prednisone 60–80 mg
daily during the first 5 days and then
tapered over the next 5 days)

♦ A lesion which affected the lingual nerve
just distal to its junction with the
chorda tympani would present as follows:
♦ Loss of secretion from submandibular
and sublingual glands ipsilateral to the
lesion (visceral motor component of
CN VII) Loss of taste from anterior 2/3
of tongue ipsilateral to the lesion
(special sensory component of CN VII) .

Disorders
Disorders of facial nerve- underactivity
- overactivity
Gulliane Barre Syndrome
(acute idiopathic Polyneuritis)
 Ascending paresis with depressed tendon reflexes
(acute symmetrical polyneuropathy)
 Occuring 1 to 3 weeks (occassionally upto 8 weeks)
 Follows non-specific respiratory or gastrointestinal
illness
 Specific infections such as with Herpes group of viruses
(CMV, EBvirus), campylobacteria jejuni
 After immunization

Begins with myalgia or parasthesias of the
lower limbs,followed by weakness, which
often involve abdominal, thoracic and upper
limb muscles.
 Impaired swallowing or parasthesias of the
mouth and face
Bilateral facial weakness is common
Plasmapheresis is of value

MELKERSSON ROSENTHAL SYNDROME-
 Alternating reccurent facial palsy
 facial edema
 Fissured tongue
 T/t: Intralesional corticosteroids, Surgical reduction of
granulomatous tissue.
RAMSAY HUNT SYNDROME
(geniculate herpes , otitic herpes)
 - association of facial paresis with herpetic eruptions
(blisters) along the ipsilateral external auditory meatus
 - history of recurrent viral syndrome and auricular pain
 Mostly involve hard and soft palate

Crocodile tear syndrome-
 injury to facial nerve proximal to
geniculate ganglion
So there is misdirection of nerve fibres to
lacrimal gland instead of submandibular
gland through the greater petrosal nerve
Patient lacrimates while eating.

Heerfordt’ Syndrome (Uveoparotid Fever)
 uveitis, parotitis and mild pyrexia
 Facial nerve is the most commonly involved cranial
nerve in sarcoidosis (because of the infiltration of
nerve by sarcoid granulomas)
 T/t: Corticosteroids
Mobius syndrome-
 congenital complete or partial facial nerve palsy with
or without paralysis of cranial nerves
 associated with other malformation
 Present with mask like facies,
 may be associated with squint , tongue hypoplasia,
swallowing difficulties

FOVILLES SYNDROME:
 Peripheral facial weakness
 ipsilateral conjugate horizontal gaze paresis
 Contralateral hemiparesis
MILLARD-GUBLER SYNDROME-
 contralateral hemiparesis
 abducens palsy
 Variable facial nerve palsy

Disorders of overactivity
Habit spasm of the face (Nervous twitch)
 Characterized by stereotypical, repetitive facial movements
 T/t: Reassurance
Essential Blepharospasm
 Form of cranial dystonia (limited to the orbicularis oculi
muscle)
 Excessive blinking
 Blinking gradually intensifies in character, insidiously
becoming a spasm
 Disease progresses, the eye closure become so frequent and
prolonged that the patients functionally blind.

Meige’s Syndrome
(Blepharospasm , Oromandibular Dystonia)
- Dystonic involvement of the lower cranial muscles
(mouth retraction , jaw opening or closing, facial grimacing) ,
neck ,
vocal cords( spastic dysphonia) and
limbs .
Facial Myokymia
- Continuous ,undulating, involuntary movement of the facial
muscles
- Involving the periocular and orbicularis oris muscle
- Associated with Cerebellopontine angle tumors,
sarcoidosis,
Guillain – barre syndrome and
cardiopulmonary arrest.www.indiandentalacademy.com

Tumors
1) Facial Neuromas:
 nonmalignant fibroid growth may grow in the
facial nerve itself, producing a gradually
progressive facial nerve paralysis.
 Arise from any segment of the nerve from the
cerebellopontine angle to the extratemporal
peripheral portion .
 Slowly progressive or sudden facial weakness,
often preceded by facial twitching,

2)Acoustic neuromas:
 non-malignant fibrous growths, originating from the
balance or hearing nerve, that do not metastasize.
 Impair hearing,facial nerve function
 Acoustic tumors are in intimate contact with the facial
nerve
 Temporary paralysis of the face and muscles which close
the eyelids is common following removal of an acoustic
tumor.
 Facial paralysis may result from nerve swelling or nerve
damage.

3)Parotid gland tumours:
 Facial nerve paralysis associated with a parotid
gland tumour classically denotes malignancy.
 facial nerve paralysis secondary to Warthin’s
tumour of the parotid gland.
 It is important for clinicians to be aware that, on
rare occasions, facial nerve dysfunction may result
from benign parotid disease.
 Parotid gland tumor are often associated with
carcinomatous infiltration into facial nerves

4) Schwannoma
- Facial nerve Schwannoma: predilection for geniculate
ganglion
- Occur at any site (from its origin in the pons and its exit
in the stylomastoid foramen)
- Sensorineural hearing loss
( extends in to the internal acoustic canal)
- Conductive hearing loss
( extends in to the middle ear)

Infections
Bacterial:
Lyme Disease ( Lyme Borreliosis)
 caused by group of spirochetal infection, Borrelia
burgdoferi
 bacteria may enter the body through the skin at the
site of tick bite and produce flu like symptoms.
C/F: red ring around the site of the tick bite.
- cranial neuropathies, headache, seizures and
vertigo.
T/t : i.v. Penicillin or oral Doxcycline
-

Viral:
Herpes simplex virus(HSV-1)
- most frequent cause of Bell’s Palsy
- Virus often remains dormant.
- Triggers not known but causative factor:
decreased immunity , stress, URI , lack of sleep,
etc.
- This leads to inflammatory reaction which put
pressure on nerve, compress it and resulting into
Bell’s Palsy.

Human immunodeficiency Virus-
- Can cause Bell’s Palsy.
- Early stage paralysis due to viral infection
- In later stage it may due to opotunistic infections.
Fungal
♦ Intracranial Aspergillosis:
♦ - involving the internal auditory canal and inner
ear in an immunocompetent patient
♦ C/F: facial weakness
♦ T/t : Amphotericin B

References
♦ GRAY ANATOMY 37 TH
EDITION, page no. 1107- 1110.
♦ CLINICAL ORIENTED ANATOMY 5 TH
EDITION, page no. 945-947.
♦ B D CHOURASIA’S HUMAN ANATOMY 4 TH
EDITION , VOL- 3,page
no. 138-141.
♦ BURKET’S ORAL MEDICINE DIAGNOSIS AND TREATMENT, 10 TH
EDITION, page no. 599-600.
♦ Gulam Hasan,Ashfaqul Hasan et al : the Facial Nerve : The Anatomical
and Surgical important, JK-Practioner 2005;12 (1):53-57
♦ http:// info.med.yale.edu /403.html
♦ www.physio web.org
♦ http:// www.michiganear.com/library/brochures/acoustic neuromas
♦ Pulec J L: Facial Nerve Neuroma, Ear Nose Throat J 1994;73:721-2,725-
39,743-52.

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