3. CONTENTS
INTRODUCTION
NERVE AND ITS CONDUCTION
CLASSIFICATION OF NERVOUS SYSTEM
INTRODUCTION TO FACIAL NERVE
EMBRYOLOGY
NUCLEI OF ORIGIN
FUNCTIONAL COMPONENTS
COURSE
BRANCHES AND DISTRIBUTION
GANGLIA
BLOOD SUPPLY
SURGICAL ANATOMY OF FACIAL NERVE
APPLIED ASPECTS
CONCLUSION
BIBLIOGRAPHY
3
4. A bundle of fibers
that uses electrical
and chemical signals
to transmit sensory
and motor information
from one body part to
another.
WHAT IS A NERVE?
4
5. NERVE AND ITS CONDUCTION
1. The Neuron (nerve cell)- is the structural unit
of the nervous system.
2. It transmits messages between the CNS and
all parts of the body.
5
6. NERVE AND ITS CONDUCTION
3. There are two basic types of neurons: the
sensory(afferent) and motor (efferent).
4. Sensory neurons- are capable of transmitting
the impulses from site to the CNS.
5. Motor neurons- conduct impulses from the
CNS toward the periphery.
6
10. INTRODUCTION TO FACIAL NERVE
There are 12 cranial nerves.
The Facial nerve is the 7th cranial nerve.
It is the nerve of the second branchial arch.
Hence supplies all the muscles that develop from
the mesoderm of this arch.
It is a mixed nerve with a large motor root and a
small sensory root.
10
11. MICROANATOMY OF FACIAL
NERVE
It is estimated that each of the 7000 neuron cell
bodies which extend axons from the facial
nucleus innervates 25 muscle fibers.
The smaller the ratio of muscle fibers to neuron
cell bodies , the greater is the degree of
specialized movement possible.
11
12. Diameter of facial nerve axons varies between
3-20µm and the nodes of ranvier are spaced from
0.1-1.8µm apart.
Because facial nerve fibers are myelinated the wave
of depolarization can jump from one node of ranvier
to the next, a process called saltatory conduction.
This accounts for the rapid conduction velocity of
the facial nerve, which is 70-110m/sec.
12
13. EMBRYONIC DEVELOPMENT OF
FACIAL NERVE
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 13
14. EMBRYOLOGY OF FACIAL NERVE
Weeks Features
0-4 Appearance of facio-acoustic
primordium/crest
Splitting of facial nerve
Presence of chorda tympani
5-6 Separation of facial and
acoustic nerves
Appearance of geniculate
ganglion
Formation of GPN
7 Formation of peripheral
branches
8 Formation of fallopian canal
10-15 More extensive branching
14
15. NUCLEI OF ORIGIN AND THEIR
COMPONENTS
Motor nucleus Upper face recieves bilateral innervation.
lower face receives unilateral innervation.
Muscles of facial expression.
posterior belly of digastric.
stylohyoid muscle.
stapedius.
Lacrimatory and
Superior salivatory
nucleus
Submandibular & sublingual salivary glands
lacrimal gland
Nucleus of solitary
tract ( gustatory
nucleus)
Mediates taste
15
17. FUNCTIONAL COMPONENTS - motor
Branchial motor
(special visceral efferent)
supply the muscles derived by the mesoderm of
II branchial arch which are
the muscles of facial expression;
occipitofrontalis;
posterior belly of digastric muscle;
stylohyoid, and
stapedius.
Visceral motor
(general somatic efferent)
Originates in superior salivatory nucleus and
Parasympathetic innervation of the
lacrimal,
submandibular, and
sublingual glands,
mucous membranes of nasopharynx, hard and
soft palate.
17
18. 18
Special sensory
(special visceral
afferent)
Taste sensation from the
Anterior 2/3 of tongue
Hard and soft palates.
General sensory
(general somatic
afferent)
General sensation from the skin
of
external acoustic meatus and
deeper parts of the auricle.
FUNCTIONAL COMPONENTS -
sensory
19. COURSE
1. Intra cranial course
Intra pontine course
Attachment to the brain stem
Course through posterior cranial fossa
19
3. Exit from the
cranium
4. Extracranial
course
2. Intrapetrous course
Meatal part
Facial canal part
labyrinthine segment
Tympanic segment
Mastoid segment
20. INTRACRANIAL COURSE
Intrapontine Course:
the fibers from the motor nucleus
course through the pons taking a
sharp bend around the abducent
nucleus producing internal genu of
the facial nerve and they leave the
pons between the nucleus of spinal
tract of trigeminal and the other
facial nucleus.
20
21. Attachment to the
brain stem:
The sensory and motor
roots are attached to the
lateral aspects of the
pontomedullary junction.
21INTRACRANIAL COURSE
22. INTRACRANIAL COURSE
Course Through Posterior Cranial Fossa
22
From the superficial
attachment to the brainstem
to the opening of the internal
acoustic meatus the two roots
of the facial nerve pass
laterally and forward in the cerebellopontine angle
along with vestibulochoclear nerve and
labyrinthine artery. These structures together
enter the internal acoustic meatus.
23. INTRAPETROUS COURSE
Meatal segment:
It is in the internal acoustic
meatus where the motor root
is lodged in a groove on the
antero-inferior surface of the
vestibulochoclear nerve but
the sensory root separates
them.
23
At the bottom of the internal acoustic meatus , the two roots
unite to form the trunk of the facial nerve and then it enters
the facial canal.
24. i. Labyrinthine segment :
passes laterally above the
vestibule of the inner ear to
reach the anterior end of the
medial wall of the middle
ear. Here it bends backwards
at a sharp turn called the
external genu of the facial
nerve which has the
geniculate ganglion on it.
24
Facial canal part: is divided into 3 segments:
INTRAPETROUS COURSE
25. ii. Tympanic segment:
passes backwards in the
medial wall of the middle
ear till it reaches the
posterior end of this wall.
It is also known as the
horizontal part.
25INTRAPETROUS COURSE
26. iii. Mastoid segment or
vertical segment:
begins at the posterior end of
the medial wall and passes
downwards in relation to the
posterior wall of the middle
ear to reach the stylomastoid
foramen.
26INTRAPETROUS COURSE
27. EXIT FROM THE CRANIUM
The facial nerve leaves the cranium through
stylomastoid foramen
27
28. EXTRACRANIAL COURSE
The facial nerve
crosses the lateral side
of the base of the
styloid process.
It enters the
posteromedial surface
of the parotid gland.
28
29. EXTRACRANIAL COURSE
Within the gland it runs forward for a short
distance superficially to the retromandibular vein
and external carotid artery and then divides into
a)Temprofacial and
b)Cervicofacial trunks.
29
31. EXTRACRANIAL COURSE 31
The terminal branches radiate like a goose’s foot
from the anterior border of the parotid gland –
“Pes anserinus”
32. BRANCHES AND DISTRIBUTION
I. Within the facial canal:
a. Greater petrosal nerve
b. Nerve to stapedius
c. Chorda tympani nerve
II. At the exit from the styomastoid foramen:
a. Posterior auricular nerve
b. Nerve to the digastric
c. Nerve to stylohyoid
32
33. III. Terminal branches within the parotid gland:
a. Temporal nerve
b. Zygomatic nerve
c. Buccal nerve
d. Marginal mandibular
e. Cervical branch
IV. Communicating branches with adjacent
cranial and spinal nerves
33
36. Greater Petrosal Nerve
Carries gustatory and parasympathetic fibers.
Arises from the geniculate ganglion of the facial nerve, and
enters the middle cranial fossa through the hiatus for the
greater petrosal nerve on the anterior surface of the
petrous temporal bone.
It proceeds towards the foramen lacerum where it joins the
deep petrosal nerve which carries sympathetic fibers to
form nerve of petrygoid canal.
36
37. The nerve of the pterygoid canal passes through the pterygoid
canal to reach the pterygoplatanine ganglion. The
parasympathetic fibers relay in this ganglion.
Postganglionic parasympathetic fibers arising in the ganglion
ultimately supply the lacrimal gland and the mucosal glands of
the nose, palate and pharynx.
The gustatory or taste fibers do not relay in the
ganglion and are distributed to the palate.
Greater Petrosal Nerve 37
38. Nerve To The Stapedius
Arises opposite the pyramid
of the middle ear , and
supplies the stapedius
muscle.
The muscle damps
excessive vibrations of the
stapes caused by high-
pitched sounds.
38
39. The Chorda Tympani
It runs upwards and forwards in a bony canal. It enters the
middle ear and runs forwards in close relation to the
tympanic membrane.
39
Arises in the vertical part of the facial canal about 6mm
above the stylomastoid foramen.
40. The Chorda Tympani
It leaves the middle ear by passing through
pterygopalatine fissure. It then passes medial to
the spine of the sphenoid and enters the
infratemporal fossa. Here it joins the lingual
nerve through which it is distributed.
It carries the preganglionic fibres to the
submandibular and sublingual salivary glands
and taste fibres from the anterior two-thirds of
the tongue.
40
42. Posterior auricular nerve
Arises just below the stylomastoid foramen.
It ascends between the mastoid process and the
external acoustic meatus and supplies:
42
POSTERIOR AURICULAR BRANCH
a) The posterior
auricularis
b) The occipitalis
c) The intrinsic muscles
on the back of the
auricle.
43. The digastric branch
Arises close to the posteriorauricular nerve.
It is short and supplies the posterior belly of
digastric .
43
44. Stylohyoid branch
It arises with the digastric branch.
It is long and supplies the stylohyoid muscle.
44
49. Ganglia Associated With Facial
Nerve
-the taste fibers present in the nerve are present in the
genigulate ganglion.
49
I. GENICULATE GANGLION :
is located on the first bend
of the facial nerve, in
relation to the medial wall of
the middle ear.
-it is a sensory ganglion
50. II. SUBMANDIBULAR GANGLION:
- is a parasympathetic ganglion for relay of secretomotor fibers to
the submandibular and sublingual salivary glands.
50
51. II. SUBMANDIBULAR GANGLION:
the motor or parasympathetic fibers pass from the
lingual nerve to the ganglion through the posterior
root. These are preganglionic fibers that arise in the
superior salivatory nucleus and pass through the
facial nerve- the chorda tympani and the lingual
nerve to reach the ganglion.
The fibers relay in the ganglion.
51
53. iii. PTERYGOPLATINE GANGLION (SPHENOPALATINE
GANGLION):
53
• Is the largest parasympathetic peripheral ganglion.
• It serves as a relay station for secretomotor fibers to the
lacrimal gland and to the mucous glands of the
nose,paranasal sinuses,palate and the pharynx.
• It is also called hay fever ganglion.
54. 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
54
55. BLOOD SUPPLY
55
Venous drainage is into
the venae comitantes
of the superficial
petrosal and
stylomastoid viens.
The arteries form a external plexus lying within the
epineurium and an internal plexus which is intraneural.
56. FUNCTION
The facial nerve is responsible for:
-Contraction of the muscles of the face
-Production of tears from a gland (Lacrimal gland)
-Conveying the sense of taste from the anterior 2/3rd of the
tongue (via the Chorda tympani nerve)
-The sense of touch at auricular conchae
56
58. Variations of facial nerve
branching patterns
Flower (1961) reviewed seven variations
including changes in angulation.
Curtis and May (1986) reported a case of
progressive facial nerve canal along the internal
auditory canal, creating a double internal
auditory canal.
58
59. Variations of facial nerve
branching patterns
Caprosa and Klassen (1966) observed bifurcation
of facial nerve just distal to the geniculate
ganglion.
Duncan, Shea and Sleeckx (1967) found
bifurcation of branches of the chorda tympani.
59
63. Level Of Nerve Injury And Symptoms
63
The facial nerve has a wide range of functions. Thus,
damage to the nerve can produce a varied set of symptoms,
depending on the site of the lesion.
65. Paresis: weakness of facial muscles to perform
motor functions is called paresis (partial
dysfunction)
Paralysis: Total flaccidity of facial muscles to
perform motor function is called facial paralysis
65
66. SUPRANUCLEAR FACIAL
PARALYSIS
It is usually hemiplegia-
it is the lower part of the
face that is chiefly
affected, while the upper
part remains
unaffected,i.e.,the
frontalis and orbicularis
oculi muscles escape.
66
This is because there is bilateral control
67. INFRA NUCLEAR FACIAL
PARALYSIS
The lower motor
neuron lesion of
facial nerve cause
paralysis of all facial
muscles on the same
side.
67
In LMN injury both the upper and lower parts will be involved
68. HOUSE-BRACKMAN(1985)
CLASSIFICATION FOR FACIAL FUNCTION
Grade I-normal function without weakness.
Grade II-mild dysfunction with slight facial asymmetry with a minor
degree of synkinesis.
Grade III-moderate dysfunctions-obvious , but not disfiguring, asymmetry
with contracture and/or hemifacial spasm,but residual forehead motion
and incomplete eye closure.
Grade IV-moderately severe dysfunction- obvious, disfiguring asymmetry
with lack of forehead motion and incomplete eye closure.
Grade V-severe dysfunction-asymmetry at rest and only slight facial
movement.
Grade VI-total paralysis-complete absence of tone or motion.
68
69. BELL’S PALSY
It is defined as an idiopathic
paresis or paralysis of the facial
nerve of sudden onset.
The name was ascribed to SIR
CHARLES BELL, who in 1821
demonstrated the separation of
motor and sensory innervation
of face.
69
70. INCIDENCE- 15-40 cases per 1 lakh cases
SEX PREDILECTION- women more affected than men.
3.3 more times common in pregnancy and in the third
trimester.
AGE- can occur at any age, common in middle aged
people.
SIDE INVOLVMENT- can be equally seen, usually unilateral.
70
72. CLINICAL FEATURES
72
Inability to smile, close eye and raise eyebrow.
Whistling is impossible
Drooping of corners of the mouth.
Slurred speech
Inability to close eyelid (Bell’s sign)
Loss of blinking reflex
Inability to wrinkle forehead
Mask like appearance of the face.
Loss or alteration of taste.
73. 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.
73
74. RAMSAY HUNT SYNDROME
A special form of
herpes zoster infection
of the geniculate
ganglion with the
involvement of the
external ear and the
oral mucosa
74
75. MELKERSSON ROSENTHAL SYNDROME
Recurrent attacks of facial paralysis
Associated with multiple episodes of non-pitting,
non-inflammatory painless edema of the face
Chelitis granulomatosa
Fissured tongue 75
76. MOBIUS SYNDROME
Results from the
underdevelopment of
cranial nerve VI and VII
The VI cranial nerve
controls lateral eye
movement, and the VII
cranial nerve controls
facial expression and is
manifested in infancy.
76
77. MOBIUS SYNDROME
Because of partial or
complete facial paralysis,
the infant exhibits :
No change in facial
expression (mask like
appearance)
Failure to close eyes
during sleep.
Mouth may remain
partially open
77
78. CROCODILE TEARS SYNDROME
Due to injury to facial nerve
proximal to the geniculate ganglion,
there may be a misdirection of
nerve fibres to lacrimal gland
instead of going to submandibular
gland, through the greater petrosal
nerve. As a result patient lacrimates
is termed as ‘crocodile tear
syndrome’ and can be treated by
dividing greater petrosal nerve.
78
79. CLINICAL NOTES
Parotid disease: Parotid tumours, trauma or
surgery may damage branches of the facial
nerve. This would result in an ipsilateral facial
palsy with wasting and functional loss. It would
be unlikely to recover.
PATEY’S OPERATION
79
80. CLINICAL NOTES
Stapedial hyperacusis: Dysfunction of the
smallest muscle supplied by the facial nerve can
cause a distressing symptom.
Stapedius dampens the movements of the
ossicular chain and if it is inactive, sounds will be
distorted and echoing.
This is hyperacusis.
80
81.
This branch passes
on or just below the
lower margin of the
mandible. It is
superficial even to
the palpable facial
arterial pulse and is
thus liable to injury. 81
The marginal mandibular branch of the facial
nerve:
CLINICAL NOTES
82. 82
The marginal mandibular branch of the facial
nerve:
CLINICAL NOTES
Section of this
nerve would
result in
paralysis of the
muscles of the
corner of the
mouth:
drooling would
occur.
83. Facial nerve injury in babies: As the mastoid process is
rudimentary(not completely developed) at birth, the facial
nerve is more easily damaged in babies. Birth injuries or
other trauma, can therefore cause an ipsilateral facial palsy.
83
This is serious since
buccinator, supplied by
VII, is necessary for
sucking(feeding).
CLINICAL NOTES
84. Acoustic neuroma: This is a tumour of Schwann cells on the
vestibular nerve in the IAM(Internal Acoustic Meatus). Since
the tumour grows within a bony canal it may compress the
facial and vestibulocochlear nerves causing a particular type
of deafness (nerve deafness) and an ipsilateral facial
palsy.
84
CLINICAL NOTES
85. Cerebellopontine angle
tumours : Tumours in this
region would cause signs and
symptoms of damage to the
facial and vestibulocochlear
nerves and cerebellar signs.
These include facial palsy,
deafness, vertigo and poor
coordination. 85
CLINICAL NOTES
86. Evaluation of Nerve function
HISTORY is of vital importance to establish the onset
characteristics, duration and degree of recovery.
Previous trauma, surgery or infection may help in arriving at a
diagnosis
Examination of the face at rest and movement.
Radiologic evaluations : CT, MRI
Nerve function tests : topognostic testing, ear pain, taste,
tearing, salivation, stapeus reflex/auditory testing, vestibular
testing, electronystagmography, Electrophysiologic testing:
Evoked electromyography.
86
87. CONCLUSION
The most important thing about the intracranial course of
Facial Nerve is its relationship to the middle ear.
The most important thing about the extracranial course is
its relationship to the parotid gland.
Hence a complete understanding of its anatomy is essential
and care should be taken during surgical procedures.
87
88. REFERENCES
Gray’s anatomy 2nd edition
Head and neck anatomy- Berkovitz ; Moxham
Essentials of human anatomy : 9th edition. Russell T ; William
B.D.Chaurasia’s Human Anatomy 4th edition
Clinical Anatomy 2nd edition -Neeta V Kulkarni
The Facial Nerve – May’s 2nd edition
Handbook of local anaesthesia- Stanley F Malamed 5th edition
Shafer’s Textbook of Oral Pathology -5th edition
Atlas of clinical gross anatomy- Kenneth , John , Pedro.
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