by humra shamim

1. Facial Nerve:Neuroanatomy
by Humra shamim

2. 1. Introduction
2. Embryology
3. Nuclei of origin
4. Course & Relations
5. Branches of facial nerve
6. Ganglia associated with facial nerve
7. Blood supply
8. Disorders of facial nerve
Contents

3.  The Facial nerve is the seventh of twelve paired cranial nerves, it
is a mixed nerve with motor and sensory roots.
 It emerges from the brain stem between the pons and the
medulla, controls the muscles of facial expression
 It functions in the conveyance of taste sensations from the
anterior two thirds of the tongue and oral cavity
 It also supplies preganglionic parasympathetic fibres to several
head and neck ganglia
Introduction

4. • It contains approx. 10,000 fibres out of which 7000 are carried
by motor root and 3000 are sensory and parasympathetic
(nerve of Wrisberg)

5. Embryology
 The facial nerve is developmentally derived from the hyoid
arch, which is the second branchial arch
The motor division of facial nerve is derived from the basal
plate of the embryonic pons
The sensory division originates from the cranial neural crest

6. 3rd week
• Facioaccoustic primordium develops giving raise to 7th
and 8th cranial nerves
• FIRST distinguishable feature of facial nerve

7. Facial nerve embryology: 4th week
 By the end of the 4th week,
the facial and acoustic
portions are more distinct
 The facial portion extends to
placode
 The acoustic portion
terminates on otocyst

8. Facial nerve embryology: 5th week
 Early 5th week, the
geniculate ganglion
forms from distal part of
primordium
 It separates into 2
branches: main trunk of
facial nerve and chorda
tympani

9. Facial nerve embryology: 6th week
 Near the end of the 5th
week, the facial motor
nucleus is recognizable
 The motor nuclei of VI and
VII cranial nerves initially
lie in close proximity.
 The internal genu forms as
metencephalon elongates
and CN VI nucleus ascends

10. Facial nerve embryology: 7th week
 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

11. 10th to 12th week
• Facial nerve makes 2nd genu
• Peripheral branches are completely developed

12. At term
• Almost similar to that of adult
• More superficial as the mastoid process is absent

13. Age 1 to 3
• Mastoid process develops
• Nerve is displaced medially and inferiorly

14. Applied anatomy
• Ritchers cartilage forms the
bones of 2nd pharyngeal
arch (stapes, styloid
process, cornua of hyoid
bone)
• Any abnormality should
prompt nerve damage
• Facial canal is derived from
ritchers cartilage

15. • Congenital atresia is associated with facial
nerve palsy in 50% of cases

16. Treacher collins syndrome
(mandibulo facial dysostosis)
There is a set of typical symptoms within Treacher Collins
Syndrome
The OMENS classification was developed as a comprehensive
and stage-based approach to differentiate the diseases.
O; orbital asymmetry
M; mandibular hypoplasia
E; auricular deformity
N; nerve development and
S; soft-tissue disease

17. Facial Nerve involvement in
Treacher collins syndrome
N0: No facial nerve involvement
N1: Upper facial nerve involvement (temporal or
zygomatic branches)
N2: Lower facial nerve involvement (buccal, mandibular or
cervical)
N3: All branches affected

18. Goldenhars syndrome
(oculoauriculo vertebral dysplasia)
It is a wide spectrum of congenital anomalies that involves
structures arising from the first and second branchial arches.
Features of hemi facial microsomia, anotia, vertebral
anomalies, congenital facial nerve palsy.

19. Cardiofacial Syndrome
Unilateral facial paralysis involving only the lower lip
and congenital heart disease
 The facial paralysis in these patients involves only
those muscles concerned with pulling the lower
lip downwards and outwards
 These are the
mentalis, depressor labii inferioris and depressor
anguli oris muscles

20. All are supplied by the mandibular marginal branch of the
facial nerve
The paralysis is only recognizable when the patient
talks, smiles or cries

21. Moebius syndrome (congenital facial diplegia)
 Abnormal VI ,VII,XII Nerve nuclei
 Facial Nerve absent / smaller
 Congenital Extra ocular muscle & facial palsy
Congenital Facial nerve palsy

22. Diff between adults and children
child
adult
1. Absent mastoid process
and incomplete tympanic
ring
2. Chorda tympani exits
through stylomastoid
foramen
3. Second genu is very acute
and lateral
4. When exits from
stylomastoid foramen is
more anterior
5. Nerve superficial over
angle of the mandible
1. Matoid process and ring is
complete
2. Chorda tympani exits
proximal to stylomastoid
foramen
3. Less acute and medial
4. Due to parotid it is less
anterior
5. Less superficial

23. FACIAL NERVE NUCLEI

24. Facial nerve nuclei components
• Branchiomotor (main motor)
• Visceromotor (supra salivatory nucleus)
• Special sensory ( tractus solitarius)
• General sensory (upper part of spinal nucleus of trigeminal
nerve)

25. 1
.1 Motor nucleus of facial nerve (SVE):
It lies in the lower part of the pons

26. 2. Superior salivatory nucleus (GVE):
It lies in the pons lateral to the main motor nucleus of VII
and gives rise to secretomotor parasympathetic fibers that pass
in greater superficial petrosal nerve and chorda tympani.

27. 3. Nucleus solitarus (SVA):
It lies in the medulla, receives the taste sensation from the
anterior 2/3 of the tongue via the central processes of the
cells of the geniculate ganglion of the facial nerve

28. 4. GSA fibers :
Through these, fibers to acoustic meatus & back of auricle through
communication from auricular branch of vagus. These fibers terminate in
main sensory nucleus & spinal nucleus of 5 th nerve

30. • Motor component forms the largest component
of facial nerve nuclei
• The other 3 components form a distinct facial
sheath called nervus intermedius

31. Remember!!
• The sensory fibres have their cell bodies in the geniculate
ganglion
• They are bipolar
• One arm extending to periphery
• Other arm extending to the pons

32. Course Of The Facial Nerve

33. Course of the facial nerve
Has six segments
• Intracranial segment
• Intratemporal segment
Meatal segment
Labrynthine segment
Tympanic segment
Mastoid segment
• Extratemporal segment

35. Intracranial segment (23 to 24mm)
• From pons to internal acoustic meatus
• Motor fibres loop over the abducens nerve forming
facial colliculus in the floor of the fourth ventricle
• Joined by the nervus intermedius
• Together with 8th nerve cross CP angle
• Lies ventral to 8th nerve

36. Applied anatomy
• Intracranial portion lacks
epineurium
• Regained once it enters facial
canal
• surgery within the CP angle
(schwannoma) makes the
nerve vulnerable for
iatrogenic injury and makes it
difficult to identify it during
dissection of a schwannoma
as there is no connective
tissue element separating it
from the tumour

39. Meatal segment (8 to 10mm)
• IAC to meatal foramen
• Located anterosuperior to
vestibulo cochlear nerve
• Superior to crista transversa
/falciform crest and anterior
to crista verticalis ( bills bar)
• NO branches

40. Applied anatomy
• Within the meatus, the facial nerve has no separate sheath,
but shares dural investment with the nervus intermedius and
the vestibulocochlear nerve and is bathed in cerebrospinal
fluid (CSF), again making it vulnerable to surgical
manipulation.

41. Labrynthine segment (3 to 5 mm)
• Shortest division
• From entry of facial canal up
to the genu
• Susceptible to vascular injury
• Enters the facial canal
between cochlea and vestibule
and runs posteriorly

42. Applied anatomy
• The periosteum is thicker here than the entire facial canal
• This should be cut if decompression to be performed
• There are no anastomosing arterial arcades in this area and it
is the part of the facial nerve most vulnerable to ischaemia.
Owing to its bottleneck-like anatomical nature, it is also the
part of the facial nerve that most probably suffers from
ischaemia in the event of oedema following trauma or
inflammation

43. Applied anatomy
• During a translabyrinthine approach the labyrinthine segment
is at risk while drilling along the superior semicircular canal
• The labyrinthine segment is also that part of the facial nerve
most likely to be injured in temporal bone fractures.

44. In the facial canal
• Longest bony canal of any
nerve
• Occupies 73% of the bony
canal
• Nerve makes an acute turn
of 40 to 80 degree
Applied anatomy
First genu being formed due
to the pushing of the otic
capsule (app anatomy)

48. Tympanic segment ( 8 to 11 mm)
• NO branches
• Lies beneath the LCC in the
medial wall of the middle
ear
• Passes behind the oval
window and the
promontory

49. • Passes posterior to the
cochleariform process ,
tensor tympani, and oval
window
• Just distal to pyrimidal
eminence it makes a second
turn ( second genu) passing
vertically downward as the
mastoid segment

50. Applied anatomy
• Nerve may prolapse against the arch of stapes
• Bifurcate around stapes
• Course below the oval window
• More acute turn, susceptible to injury in
antrotomy

51. Applied anatomy
• Bony wall of the tympanic segment is dehiscent in 35 to 55%
of cases
• ASOM in children and neonates present with facial nerve
neuropraxia

52. Mastoid segment (10 to 14 mm)
• Extends to the stylomastoid
foramen with 3 branches
• Nerve to stapedius
• Chorda tympani
• Nerve from the auricular
branch of the vagus nerve (
pain fibres from the
posterior part of the
external acoustic meatus

53. Applied anatomy
• Normal function of stapedius in congenital facial palsy
• Animal studies show separate neurons other than main
motor nucleus

54. Applied anatomy
• Referred otalgia in bells palsy, vesicular eruption in herpes
zoster due to sensory function in ear

55. Chorda tympani nerve
 It arises from the facial nerve 6 mm above the
stylomastoid foramen and runs upwards to perforate the
posterior bony wall of the tympanic cavity.
 It then passes forwards on the medial surface of the
tympanic membrane between its fibrous and mucous
layers crossing the handle of the malleus.

56. • Comes out through
petrotympanic fissure to
infratemporal fossa
• Joins the lingual nerve
• Through lingual nerve it
supplies secretomotor
fibres to submandibular
ganglion
• Taste fibres from anterior
2/3 of the tongue

57. At the exit from the stylomastoid foramen
1- Posterior auricular nerve:
to the auricularis posterior and the occipital belly of the
occipitofrontalis muscle.
2- Digastric branch:
to the posterior belly of digastric muscle
3- Stylohyoid branch:
to the stylohyoid muscle

58. Extra temporal segment
• Passes between posterior belly of digaastric and
stylohyoid muscles and enters the parotid gland
• Lies between superficial and deep lobes of the gland
• From the anterior border of the gland 5 branches emerge

60. Terminal branches

61. The temporal branches of the facial nerve (frontal branch
of the facial nerve) crosses the zygomatic arch to the
temporal region, supplying the auricularis anterior and
superior, and joining with the zygomaticotemporal
branch of the maxillary nerve, and with the
auriculotemporal branch of the mandibular nerve.
TERMINAL BRANCHES

62. The zygomatic branches of the facial nerve (malar
branches) run across the zygomatic bone to the lateral
angle of the orbit.
Here they supply the Orbicularis oculi, and join with
filaments from the lacrimal nerve and the
zygomaticofacial branch of the maxillary nerve.

63. The Buccal Branches of the facial nerve (infraorbital
branches), of larger size than the rest of the branches,
pass horizontally forward to be distributed below the
orbit and around the mouth.

64. MUSCLE ACTION
Risorius Smile
Buccinator Aids chewing by holding cheeks flat
Levator Labii Superioris Elevates upper lip
Levator labii superioris alaeque nasi Snarl
Levator Anguli Oris Soft smile
Nasalis Flare Nostrils
Orbicularis oris muscle Purse Lips
Depressor Septi Nasi Depresses Nasal Septum
Procerus Moves Skin of Forehead
The buccal branch supplies these muscles

65.  The marginal mandibular branch of the facial nerve
passes forward beneath the platysma and depressor
anguli oris.
 It supplies the muscles of the lower lip and chin, and
communicating with the mental branch of the
inferior alveolar nerve.

66.  The cervical branch of the facial nerve runs forward
 It forms a series of arches across the side of the neck
over the suprahyoid region.
 One branch descends to join the cervical cutaneous
nerve from the cervical plexus; others supply the
Platysma. Also supplies the depressor anguli oris.

67. Applied anatomy
• Mandibular branch in 20% 2cm below mandible
in submandibular area can lead to paralysis of
mouth depressors
• Temporal branch is superficial to aponeurotic
system over the zygomatic arch, (hence at risk
during surgery )

68. GANGLIAASSOCIATED
WITH THE FACIAL NERVE
Geniculate ganglion
Submandibular ganglion
Pterygopalatine ganglion

69. Geniculate Ganglion
The geniculate ganglion (from Latin genu, for "knee") is an L-
shaped collection of fibers and sensory neurons of the facial
nerve located in the facial canal of the head.
It 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.

70. Submandibular Ganglion
 The submandibular ganglion is small and fusiform in
shape. It is 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 (itself a branch of the
mandibular nerve, CN V3). It is 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.

72. Pterygopalatine Ganglion
The pterygopalatine ganglion (meckel's ganglion, nasal
ganglion or sphenopalatine ganglion) is a parasympathetic
ganglion found in the pterygopalatine fossa.
It's largely innervated by the greater petrosal nerve (a
branch of the facial nerve); and its axons project to the
lacrimal glands and nasal mucosa

73. Central connections

74. Motor circuit

75. Secretomotor circuit

77. Facial Nerve: Functional Components
 Special Visceral Efferent/Branchial Motor
 General Visceral Efferent/Parasympathetic
 General Sensory Afferent/Sensory
 Special Visceral Afferent/Taste

79. General Visceral Efferent/Parasympathetic
Superior salivatory nucleus (pons)
nervus intermedius
greater/superficial petrosal nerve
facial hiatus/middle cranial fossa
joins deep petrosal nerve (symp fibers from cervical plexus)
through pterygoid canal (as vidian nerve)
pterygopalatine fossa
spheno/pterygopalatine ganglion
postganglionic parasympathetic fibers
joins zygomaticotemporal nerve(V2)
lacrimal gland & seromucinous glands of nasal and oral cavity

80. Superior salivatory nucleus
nervus intermedius
chorda tympani
joins lingual nerve
submandibular ganglion
postganglionic parasympathteic fibers
submandibular and sublingual glands

81. Special Visceral Afferent/Taste
Postcentral gyrus
nucleus tractus solitarius
nervus intermedius
geniculate ganglion
chorda tympani
joins lingual nerve
anterior 2/3 tongue, soft and hard palate

82. Extratemporal part of the facial nerve
• Tragal pointer: nerve is identified 1 cm inferior and deep to
this
• Posterior belly of digastric muscle : at its insertion to mastoid
process nerve exits stylomastoid foramina anterior to it

83. Blood supply

84. Facial Nerve 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

85. Stylomastoid artery
(branch of posterior auricular artery) – mastoid
segment
Posterior auricular artery supplies the facial nerve at
& distal to stylomastoid foramen
Venous drainage parallels the arterial blood supply

87. Applied anatomy
• The Labrynthine portion does not have any overlap
• Petrosal artery alone
• More vulnerable for ischemia

88. Applied anatomy
• Recurrent paralysis may be due to sudden compressiion and
decompression by a tumor like vestibular schwannoma
• In vestibular schwannomas only 10% of facial neurons are
required for normal facial function
• Vestibular schwannomas rarely present with facial weakness
• Presence of facial weakness facial schwannoma to be ruled out

89. Disorders of Facial Nerve
1. Supra nuclear type:
Features:
a) Paralysis of lower part of face (opposite side)
b) Partial paralysis of upper part of face
c) Normal taste and saliva secretion
d) Stapedius not paralysed
Facial Nerve Lesions

93. 2. Nuclear type:
Features:
a) Paralysis of facial muscle (same side)
b) Paralysis of lateral rectus
c) Internal strabismus

94. b) Injury distal to geniculate ganglion
Features:
i. Complete motor paralysis (same side)
ii. No hyper acusis
iii. Loss of corneal reflex
iv. Taste fibers affected
v. Facial expression and movements paralysed
vi. Pronounced reaction of degeneration

95. Lesion
distal to
geniculate
ganglion

96. c) Injury at stylomastoid foramen
• Condition known as Bell’s Palsy

97. Background of BELL’S PALSY
First described more than a century
ago by Sir Charles Bell
Yet much controversy still surrounds
its etiology and management
.
Bell palsy is certainly the most
common cause of facial paralysis
worldwide

98. Demographics of Bells palsy
Race: slightly higher in persons of Japanese descent.
Sex: No difference exists
Age: highest in persons aged 15-45 years.
Bell palsy is less common in those younger than 15 years and in
those older than 60 years.

99. Pathophysiology of Bells palsy
Main cause of Bell's palsy is latent herpes viruses (herpes
simplex virus type 1 and herpes zoster virus), which are
reactivated from cranial nerve ganglia
Polymerase chain reaction techniques have isolated herpes
virus DNA from the facial nerve during acute palsy

100. Inflammation of the nerve initially results in a reversible
neurapraxia
Herpes zoster virus shows more aggressive biological
behaviour than herpes simplex virus type1
Bell's phenomenon is the upward diversion of the eye
ball on attempted closure of the lid is seen when eye
closure is incomplete.

101. I. Unilateral involvement
II. Inability to smile, close eye or raise eyebrow
III. Whistling impossible
IV. Drooping of corner of the mouth
V. Inability to close eyelid (Bell’s sign)
VI. Inability to wrinkle forehead
VII. Loss of blinking reflex
VIII. Slurred speech
IX. Mask like appearance of face
X. Loss/ alteration of taste
Features of Bell’s Palsy

102. Diagnosis of Bells palsy
By exclusion
Criteria
Paralysis or paresis of all muscle groups of one side of the face
Sudden onset
Absence of signs of CNS disease
Absence of signs of Ear disease

103. Medical treatment
Corticosteroids :
Prednisolone 1 mg/kg/day 7-10 days
Corticosteroids combine with antiviral drug is better
Acyclovir 400 mg 5 times/day
Famciclovir and valacyclovir 500 mg bid

104. Surgical treatment
Facial nerve decompression
Indication:
Completely paralysis
ENoG less than 10% in 2 weeks
Appropriate time for surgery is 2-3 weeks after paralysis

105. It focuses on protecting the cornea from drying and
abrasion due to problems with lid closure and the tearing
mechanism.
Lubricating drops should be applied hourly during the day
and a simple eye ointment should be used at night.
Eye care

106. Treatment consists of Infra-red radiation on affected
side of the face at 2 ft (60cm) ,followed by interrupted
galvanism on affected side
Treatment was given daily at first few weeks & later thrice
weekly.
All patients are instructed to massage the face daily
There is general agreement that 70-80% of these patients
recover completely,while the reminder develop various
sequelae within one to three months

107. Bibliography
• Scott-Browns Otorhinolaryngeology, Head and Neck
Surgery, 8th edition, Miachel Gleeson etal CRC
press publication
• Endoscopic ear surgery-Prisutti,Livio.
• Grays Anatomy, 40th edition The Anatomical basis
of Clinical practice, Susan Standring, Churchill
Livingstone Elsivier publications
• Clinical Neuroanatomy, 7th edition, Richard S.
Snell, Lippincott Williams and Wilkins publications
• McMinns and Abraham’s clinical atlas of human
anatomy,7th edition.
• K.J. Lee’s Essential Otolaryngeology, Head and Neck
Surgery 10th edition McGrawHill publications

108. Thank you