The facial nerve has three divisions - intracranial, intratemporal, and extratemporal. In the intratemporal portion, it passes through four segments within the facial canal: meatal, labyrinthine, tympanic, and mastoid. It gives off several branches including the chorda tympani and nerve to stapedius. The facial nerve exits the skull through the stylomastoid foramen and divides into five terminal branches in the parotid gland. Knowledge of the facial nerve's complex anatomy is important for ear and parotid surgeries.

1. FACIAL NERVE ANATOMY
Presented by,
Dr. Aiswarya S Gopan
Moderated by,
Dr. C. H. Venkata Subbaiah

2. INTRODUCTION
 VII Cranial Nerve - Mixed Nerve
 Motor , Sensory , parasympathetic fiber
 Motor root – facial nerve proper
 Sensory & Parasympathetic – carried by “NERVUS
INTERMEDIUS” (Nerve of Wrisberg)
11/25/2021 2

3. EMBRYOLOGY
11/25/2021 3
• The facial nerve is developmentally
derived from the hyoid arch, which
is the second branchial arch.
• 3rd week of gestation: The first
distinguishable facial nerve
feature - facioacoustic
primordium or crest.
• 3rd month of gestation: Facial
nerve course, branching pattern,
anatomical relationships are
established
• At term: similar to that of adult,
placed superficially as mastoid
process is absent.
• By 4yrs: nerve displaced medially
and inferiorly as mastoid process
develops.

4. APPLIED ANATOMY
• Reichert’s cartilage forms the bones of 2nd
pharyngeal arch(stapes, styloid process,
cornua of hyoid bone)
• Facial canal is also derived from ritchers
cartilage.
• Any abnormality in the developmental
process of ritchers cartilage would prompt
damage to the facial nerve.
11/25/2021 4

5.  Facial Nerve has 3nuclei
 Motor nucleus – lower pons below
4 th ventricle
 Superior salivatory nucleus –
dorsal to motor nucleus
 Nucleus of tractus solitarius –
medulla oblongata
11/25/2021 5
APPLIED ANATOMY
FACIAL NERVE NUCLEI

6. FACIAL NERVE: TYPES OF FIBERS
11/25/2021 6
 Special Visceral
Efferent: Branchial
Motor
 General Visceral
Efferent (motor):
Parasympathetic
 General Sensory
Afferent: Sensory
 Special Visceral
Afferent (sensory):
Taste

7. DISTRIBUTION OF FACIAL NERVE
FIBERS
11/25/2021 7

8. FUNCTIONAL
COMPONENT
NUCLEI NERVE DISTRIBUTION FUNCTION
GVE
Superior salivatory
nucleus (lies in the
pons lateral to the
main motor nucleus of
VII )
Greater superficial
petrosal nerve
Chorda tympani
Lacrimal gland,
Submandibular and
sublingual salivary
glands.
Preganglionic
Secretomotor
SVE
Motor nucleus of facial
nerve (lies in lower
part of pons)
Motor branches
Muscles of facial
expression, stylohyoid,
posterior belly of
digastric, platysma and
stapedius.
Facial expression
SVA
Nucleus of tractus
solitarius (lies in
medulla)
Chorda tympani
Taste buds in the
anterior 2/3rd of tongue
except vallate papillae
Taste sensations
GSA
Spinal nucleus of Vth
nerve
Post auricular
nerve
Part of skin of
external ear
Exteroceptive
sensation
11/25/2021 8

9. COURSE OF FACIAL NERVE
Has 3 divisions:
 Intracranial division
 Intratemporal division
 Meatal segment
 Labrynthine segment
 Tympanic segment
 Mastoid segment
 Extratemporal division
11/25/2021 9

10. COURSE OF FACIAL NERVE CONT..
• The nerve arises in the pons in
brainstem.
• It begins as two roots
• Large motor root.
• Small sensory root (Nervous
intermedius)
• The two roots travel through the internal
acoustic meatus.
11/25/2021 10

11. MOTOR ROOT
 The main trunk of the nerve
(motor root of the facial
nerve), continues anteriorly
and inferiorly into the
parotid gland.
 Within the parotid gland, the
nerve terminates by splitting
into five branches.
 Temporal branch
 Zygomatic branch
 Buccal branch
 Marginal mandibular branch
 Cervical branch
11/25/2021 11

12. INTRACRANIAL PART
23 to 24 mm
From pons to internal acoustic
meatus
Motor fibres loop over the
abducens nerve ( CN VI) forming
facial colliculus over the floor of 4th
ventricle.
Together with CN 8th crosses CP
angle.
11/25/2021 12

13. APPLIED ANATOMY
• Intracranial part of facial nerve lacks epineurium.
• Epineurium gained after entering facial canal.
• Surgery within the CP angle (schwanomma) makes the nerve
vulnerable for iatrogenic injury.
11/25/2021 13

14. INTRATEMPORAL COURSE
 From Internal acoustic
meatus to Stylomastoid
foramen.
 Length – 28 to30 mm.
 Facial canal : Longest
bonycanal for nerve.
 4segments by 2
genus.
11/25/2021 14

15. MEATAL SEGMENT
• 8 to 10mm
• From IAM to beginning of facial
canal
• Located anterosuperior to
vestibulocochlear nerve (CN VIII)
• Lies superior to tranverse crest
(faliciparum crest) and anterior to
vertical crest ( Bills bar)
• Contains no branches.
11/25/2021 15

16. LABRYNTHINE SEGMENT
11/25/2021 16
3 to 5mm
Shortest division
From entry to facial canal up to the geniculate ganglion
Most susceptible for Bell’s palsy
Enters the facial canal between cochlea and vestibule and runs
posteriorly
Branch: Greater superficial petrosal nerve

17. APPLIED ANATOMY
Anatomical “bottle neck”:
 Most vulnerable for ischemia
 No arterial anastomosis and surrounded by dense arachniod
band
 Narrowest portion is at the meatal foramen, the junction of
int auditory canal and labrynthine segment.
 Ischemia in oedema resulting in BELL’S PALSY
 Temporal bone #- MC injured part of nerve
11/25/2021 17

18. BRANCHES FROM GENICULATE GANGLION
 Greater superficial petrosal
nerve.
 Lesser petrosal nerve
 External petrosal nerve
11/25/2021 18

19. GREATER SUPERFICIAL PETROSAL NERVE
11/25/2021 19
• Arise from geniculate ganglion
• Joins deep petrosal nerve forming Nerve of
pterygoid canal / Vidian nerve
• Travels in pterygoid canal
• Joins pterygopalatine ganglion in pterygopalatine
fossa
• Contains lacrimatory fibres; joins with zygomatico
temporal nerve (V2)
• Supply lacrimal gland ang glands around nose,
paranasal sinus and palate
• Surgical importance: landmark in middle cranial
fossa approach

20. TYMPANIC (HORIZONTAL) SEGMENT
8 to 11 mm
From geniculate ganglion to
pyramidal eminence
Lies beneath the lateral semi-
circular canal in the medial
wall of middle ear
Passes behind oval window
and promontory
Distal to pyramidal eminence
makes second genu
No branches
11/25/2021 20

21. APPLIED ANATOMY
 Processus cochleariformis -
demarcates geniculate
ganglion
 Imp landmark for 2nd genu
 Lies inf to LSCC
 Pyramidal eminence
 Between short process of
incus and LatSCC
11/25/2021 21

22. MASTOID (VERTICAL) SEGMENT
 Longest intratemporal segment ( 10 to 14 mm)
 From 2nd genu posteromedially to stylomastoid foramen anterolaterally
 Landmark – “ Digastric Ridge” identified by medial aspect of
mastoid tip
 Facial nerve leaves facial canal via stylomastoid foramen
 Has 3branches
 Chorda Tympani
 Nerve to stapedius
 Sensory auricularbranch
11/25/2021 22

23. CHORDA TYMPANI
4-5mm above stylomastoid foramen
Lateral and anterior to Facial Nerve
Passes b/w long process incus & upper part
of handle of malleus
2 types of fibers
Preganglionic parasympathetic →
Submandibular Ganglion → Postganglionic
→ submandibular & sublingual gland
Special sensory → ant 2/3rd of tongue
• Surgical importance:
• Landmark in posterior tympanotomy
• Lateral margin of facial recess
11/25/2021 23

24. EXTRACRANIAL COURSE
• From stylomastoid foramen to
Terminal branches.
• Runs in substance of parotid
• Main trunk divides forming
“Pes anserinus”
• upper temperofacial
• lower cervicofacial
• Superficial to Retromandibular
vein and Ext. carotid artery
11/25/2021 24

25. BRANCHES OF EXTRACRANIAL COURSE
Posterior auricular nerve
Digastric branch – supply post
belly of digastric
Stylohyoid branch
Terminal branches:
Temporal
Zygomatic
Buccal
Marginal mandibular
Cervical
11/25/2021 25

26. TERMINAL BRANCHES
11/25/2021 26

27. 1. Anterior inferior cerebellar artery - at the
cerebellopontine angle
2. Labyrinthine artery (branch of anterior
inferior cerebellar artery) – within internal
acoustic meatus
3. Superficial petrosal artery (branch of
middle meningeal artery) – geniculate
ganglion and nearby parts
4. Stylomastoid artery (branch of posterior
auricular artery) – mastoid segment
5. Posterior auricular artery supplies the facial
nerve at & distal to stylomastoid foramen
11/25/2021 27
BLOOD SUPPLY

28. ANATOMICAL RELATIONSHIP OF FN IN
ADULTS & CHILDREN
Child Adult
Absent mastoid process &
incomplete tympanic ring.
Chorda Tympani may exit thru
SMF
Mastoid process & complete
ring . Chorda tympani exits
separately prox to SMF
2nd genu is more acute & lateral
2nd genu less acute & more
medial
N trunk on exit from SMF is
more anterior &lateral
Parotid is more post. N trunk is
less anterior & deeper
N very superficial over angle of
mandible
N superficial over angle of
mandible
11/25/2021 28

29. CENTRAL CONNECTION OF FACIAL NERVE
• Upper part of face:
• B/L supranuclear (cortical)
innervation
• Lower part of face:
• C/L supranuclear innervation
• Importance – function of forehead
preserved in supranuclear lesions
11/25/2021 29

30. DISORDERS OF FACIAL NERVE
 Facial nerve lesions:
 Supra-nuclear type
 Nuclear type
 Peripheral lesions
11/25/2021 30

31. SUPRA NUCLEAR TYPE
 Features:
 Paralysis of lower part of face (opposite side)
 Partial paralysis of upper part of face
 Normal taste and saliva secretion
 Stapedius not paralysed
11/25/2021 31

32. NUCLEAR TYPE
 Features:
1. Paralysis of facial muscle (same side)
2. Paralysis of lateral rectus
11/25/2021 32

33. EAR &MASTOID SURGERY – SURGICAL
LANDMARKS
 Geniculate ganglion lies
behind & superior to
Processus
cochleariformis
 2nd genu lies in inferior aspect of
LSCC
 Facial nerve lies above oval window
 Incus lies lateral to Facial nerve
 Facial N runs behind Pyramid
 Facial N lies 6-8mm inferior to
Tympano-mastoid suture
 Digastric ridge – end of mastoid
segment
11/25/2021 33

34. SURGICAL LANDMARK IN PAROTID
SURGERY
11/25/2021 34
 Tympano-mastoid suture: 6-8
mm deep to this suture
 Groove between mastoid & bony
EAC: bisected by facial nerve
 Tragal pointer: 1 cm
anteroinferomedial is facial nerve
 Styloid process: lateral lies
facial nerve
 Posterior belly of digastric:
superior & parallel lies facial
nerve

35. 11/25/2021 35