The facial nerve originates from multiple nuclei in the pons and has a complex intra- and extracranial course through the temporal bone. It has six segments as it travels from the brainstem to the muscles of facial expression. Along its course it gives off several important branches including the chorda tympani, which carries taste fibers to the tongue, and branches that innervate the stapedius muscle and posterior belly of the digastric. Knowledge of the facial nerve's detailed anatomy is important for otologic and neurotologic procedures to avoid iatrogenic injury.

1. DR. CH.B. PRATHYUSHA
PG ENT
NARAYANA MEDICAL COLLEGE
25TH AUGUST 2015
FACIAL NERVE ANATOMY

2. “ Otology could be a dull way of life
with out the facial nerve arrogantly
swerving through the temporal bone
to the muscles of facial expression”
John Groves M D
(Co author of Scott and Brown)

3. EMBRYOLOGY
FACIAL NERVE NUCLEI
COURSE OF THE NERVE
SUMMARY OF THE BRANCHES
BLOOD SUPPLY
APPLIED ANATOMY

5. EMBRYOLOGY

6. Embryology
 Pons develops from metencephalon

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

9. 4th week
 Facioacoustic primordium
differentiates into 7th and 8th
cranial nerves
 Chorda tympani and main trunk can be
seen seperately
 Chorda tympani joins the mandibular
arch
 Main trunk joins the hyoid arch

11. 5th week
 Geniculate ganglion (separate
origin from that of facial nerve)
 Nervus intermedius
 Greater superficial petrosal nerve

12. 6th and 7th week
 Muscles of facial expression develop
 Middle ear develops and facial nerve
can be seen along the middle ear

13. 8th week
 Terminal branches can be seen
 Extensive branching due to
rapid caudal movement of 1st
branchial arch
 Facial nerve is distorted forming
1st and 2nd genu with GSPN as the
anchor

14. 10th to 12th week
 Facial nerve makes 2nd genu
 Peripheral branches are completely
developed

15. At term
 Almost to that of adult
 More superficial as the mastoid
process is absent

16. Age 1 to 3
 Mastoid process develops
 Nerve is displaced medially and
inferiorly

17. 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

18.  Congenital atresia is associated
with facial nerve palsy in 50% of
cases

19. Malformations of 1st and 2nd arches
Treacher Collins
Syndrome Goldenhar syndrome

20. Mobius syndrome
 Agenesis of 7th
nerve
 Agenesis of 6th
nerve
 Normal
intellegence
 Skeletal
abnormalities
 Dull facial
expression

21. 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

22. FACIAL NERVE NUCLEI

23. 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)

24. motor nucleus
 Lies in the lower part of the pons
 Lateral to the 6th CN and medial
to the 8th nerve
 Supplies the facial muscles

26. Superior salivatory nucleus
 Lies in the pons
 Medial to motor nucleus
 supplies the secretomotor
parasympathetic fibres

28. Nucleus solitarius(special sensory )
 A column of grey matter embedded in the MO
lateral to vagus nerve
 Rostral deals with taste
 Caudal part deals with GI and cardio
respiratory function.
 Dorsolateral to the facial motor nucleus
 Recieves taste sensation from the anterior
2/3 rds of the tongue

31. Upper part of spinal trigeminal
nucleus(general sensory)
 Upper part of trigeminal spinal
nucleus
 Recieves sensations from concha
and auricle through vagus nerve
 Bipolar neurons with their cell
bodies in the geniculate ganglion

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

34. 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

35. COURSE OF THE FACIAL NERVE

36. Course of the facial nerve
 Has six segments
 Intracranial segment
 Meatal segment
 Labrynthine segment
 Tympanic segment
 Mastoid segment
 Extratemporal segment

38. 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

40. 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

45. Meatal segment (8 to 10mm)
 IAC to meatal foramen
 Located anterosuperior to vestibulo
cochlear nerve
 Superior to crista transversa and
anterior to crista verticalis ( bills
bar)
 NO branches

47. 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

48. Applied anatomy
 The periosteum is thicker here than
the entire facial canal
 This should be cut if decompression
to be performed
 NO anastomosing collaterals here
making it vulnerable to ischemia
( bottle neck anatomical nature)

49. 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)

53. 3 branches
 Greater superficial petrosal nerve
 Lesser petrosal nerve
 External petrosal nerve

55.  Arises from geniculate ganglion
 Joins deep petrosal nerve
 Forms vidian nerve or nerve of
pterygoid canal
 Travels in pterygoid canal
 Joins pterygo palatine ganglion in
pterygopalatine fossa

58. Other branches
 Lesser petrosal nerve
 Joins the otic ganglion
 External petrosal nerve
 Joins the sympathetic plexus
around the middle meningeal artery

60. 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

61.  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

62. 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

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

66. 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

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

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

69. Chorda tympani nerve
 Arises 6 mm above stylomastoid
foramen
 Perforates the posterior wall of
the tympanic cavity
 Passes on the medial surface of
the tympanic membrane crossing the
handle of the malleus

70.  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

74. Extra temporal segment
 Posterior auricular nerve
supplies auricularis posterior and
occipital belly of occipitofrontalis
 Digastric branch
posterior belly of digastric muscle
 Stylohoid branch
to stylohyoid muscle

75. Afferent sensory fibres
 Sensation from
 Ear lobe
 EAC
 Tympanic membrane

77. 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

80.  Terminal branches
 Temporal
 Zygomatic
 Buccal
 Marginal mandibular
 cervical

82.  Temporal
 Runs along the lower border of the
manddible
 acts as the efferent limb of the
corneal reflex
Zygomatic
 3.Buccal (largest of all terminal
branches)

83.  Mandibular ( marginal )
 Cervical

85. 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 ) hence repairs
to be made deep

86. SUMMARY OF THE FACIAL NERVE
BRANCHES

89. CENTRAL CONNECTIONS

90. Motor circuit

91. Secretomotor circuit

94. Surgical anatomy
 Intratemporal part of the facial
nerve
 Cochleariform process: tympanic
segment is located deep to this
 Lateral semicircular canal: second
genu lies inferior to this
 Digastric ridge: stylomastoid
foramen is located anterior to it

95. 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

96. BLOOD SUPPLY

97. Blood supply of facial nerve
 4 vessels
 Labrynthine artery a branch of
anteroinferior cerebellar artery
 Superficial petrosal artery branch of
middle meningeal
 Stylomastoid artery
 Posterior auricular artery distal to
stylomastoid foramen
 Petrosal artery

98.  Stylomastoid artery:
Ascends stylomastoid foramen and
supplies upto 2nd genu
 Petrosal artery:
arises from middle meningeal
artery
anastomoses with stylomastoid
artery
reaches as far as stylomastoid
foramen

99.  Labrynthine artery
 Arises from anterior inferior
cerebellar artery
 Supplies the intra cranial part
except the genu

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

101.  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

102. UMN AND LMN LESIONS OF THE
FACIAL NERVE

103. UMN LMN
Lower part of the face is involved Both lower and upper part of the face
is involved
No bells phenomenon Bells phenomenon is seen
Taste is NOT effected Taste is effected
No hyperacusus Hyperacusis may be present if nerve to
stapedius is involved
Usually associated with hemiplegia Usually not associated unless any
pontine lesion is present causing crossed
hemiplegia
Site of the lesion is above facial nucleus
usually in the internal capsule
Usually in the nucleus or distal to the
nucleus
No wasting or atrophy Wasting or atrophy may be present

105. Bibliography
 Clinically oriented Anatomy, 6th edition,
Keith L Moore, lippincott, Williams and
Wilkins publications
 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
 K.J. Lee’s Essential Otolaryngeology, Head
and Neck Surgery 10th edition
McGrawHill publications

106. Thankyou