anatomie chirurgicale du nerf facial

1. Surgical anatomy of facial nerve
Dr Tasnia Mahmud
Trainee in Otolaryngology
Combined Military Hospital
Dhaka
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2. Surgical Anatomy of Facial
Surgical Anatomy of Facial
Nerve
Nerve
2
Otology could be a dull way of life without
Otology could be a dull way of life without
the 7
the 7th
th
cranial nerve arrogantly swerving
cranial nerve arrogantly swerving
through the temporal bone to the muscels
through the temporal bone to the muscels
of facial expression
of facial expression
---John Groves
---John Groves

3. Introduction
• Seventh cranial nerve
• Nerve of the second branchial arch
• The facial nerve consists of the facial nerve
proper and the intermedius nerve.
• Composed of fascicles that increase in number
along its course in the temporal bone.
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4. Functional components
• 10,000 motor, sensory and parasympathetic
fibres
• Motor-7000
• (main motor
nucleus-special
visceral efferent )
• Supplies to- facial
muscles and
digastric and stylohyoid muscle 4

5. ..cont
• Sensory & parasympathetic- 3000 (nerve of
Wrisberg)
• consist of
1. GVE-(sup salivatory nucleus,lacrimatory
nucleus)
2. SVA-(nucleus of the tractus solitarious)
3. Somatic afferent fibres-skin of EAC
5

6. 6

7. Origin of facial nerve
• Facial nerve is attached to
the brainstem by two
roots :
• motor and
• sensory ( nervus
intermedius)
• which are attached to the
lateral part of the lower
border of pons just medial
to eight cranial nerve.
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Intracranial course of facial nerve

8. Parts of facial nerve
Intracranial part: from pons to Internal auditory canal(IAC) 24mm
Intra-temporal part: from IAC to stylomastoid foramen .28-30mm
• Meatal segment (8mm) from the entracne of IAC to fundus
• Labyrinthine segment(3-5mm) from the fundus to geniculate
ganglia
• Tympanic segment (11mm)from geniculate ganglia to 2nd
genu
• Mastoid segment (13mm) from 2nd
genu to stylomastoid foramen
Extra-temporal part(Neck and parotid gland part
From stylomastoid foramen to termination of its peripheral branches

9. Segments of facial nerve

10. • The intracranial part of
facial nerve:
• covered by thin layer
of pia mater and is
not covered by perineurium.
• Extremely vulnerable
in C-P angle tumour
surgery.
• Difficult to identify it
during dissection of a schwannoma as
there is no connective tissue element
separating it from the tumour.
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11. Within the
meatus:
Facial nerve enters the foramen of
the IAM in its anterosuperior
segment and runs a distance of 5-12
mm to the fundus.
At the end of the IAC: pic
Within the meatus the facial nerve
shares common dural covering with
the nervous intermedius and 8th
nerve and bathed in CSF-vulnarable
to surgical manipulation
Relation to be remembered during
the middle cranial fossa
approach &
translabyrinthine approach

12. The labyrinthine segment
• Is the shortest and -thinnest
part
• Narroest part-meatal foramen-
0.68mm
• Pefriosteum is thicker here-
should be cut of if
decompression is performed.
• No anastomosing arterial
arcades –most vulnarable to
ischaemia after trauma or
imflammation
• Translabyrinthine approach-risk
• During temporal bone fracture-
vulnarable 12

13. The Geniculate Ganglion
• 1st
genu
• Affarent input-
• Somatic affarent
fibres(pain)
Sp visceral affarent
fibres(taste) synapse at this
level
• Dehiscence(15%cases)
vulnarable during surgery
• Sup semicircular canal
behind, cochlea in front and
below
13

14. The tympanic segment
• Straight
• Lies beneath the lateral
semicircular canal and
above the oval window
• At the proximal end- it
passes above and
medial to
cochleariform
process( most constant
landmark)
Dehiscence-making nerve
vulnarable to injury 14

15. 2nd
genu
It hugs the inferior aspect of
the horizontal semicircular
canal(constant)
Pyramidal eminence-
Lateral and posterior to it
which creates two recesses,
facial recess laterally and
sinus tympany medially
The posterior semicircular
canal is posterior to 2nd
genu
and marks the superior end
of the retrofacial air cells-
delineating medial aspect of
facial canal
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16. The mastoid segment
• Landmark- digastric ridge,
which can be identified as
the medial aspect of
mastoid tip.
• A line drawn between the
mastoid tip and short
process of incus marks its
path (posteromedial to
anterolateral)
• Plane of facial-lateral to the
level of tympanic annulus
(variable)
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17. 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,
runs forwards through the
gland crossing the
retromandibular vein and the
external carotid artery.
• Behind the neck of the
mandible it divides into its
five terminal branches which
emerge along the anterior
border of parotid gland
• Pes ansarina
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18. For middle ear and mastoid surgery
1. Processus cochleariform: small bony
protuberance, geniculate ganglion
anterior
2. Short process of Incus: nerve medial
3. Lateral/Horizontal SCC: nerve runs
below
4. Oval window: nerve rurns above
5. Pyramid: nerve runs behind
6. Tympanomastoid suture: nerve runs
behind
7. Digastric ridge: nerve at anterior end
Surgical landmarks of facial nerve

19. For parotid surgery:
1. Tympano-mastoid suture: 6-8 mm
deep to this suture
2. Groove between mastoid &
bony EAC: bisected by facial nerve
3. Tragal pointer: 1 cm antero-infero-
medial is facial nerve
4. Styloid process: lateral lies facial
nerve
5. Posterior belly of digastric:
superior & parallel lies facial nerve

20. Branches of Distribution
Facial canal
A.Nerve to stapedius
B.Chorda tympani
In face
A.Temporal
B.Zygomatic
C.Buccal
D.Marginal mandibular
E.Cervical
Stylomastoid
foramen
A.Posterior auricular
B.Nerve to stylohyoid
C.Nerve to digastric
(posterior belly)

21. Intra-tympanic branches

22. Greater Petrosal nerve
• Leaves at the genu
• pre ganglionic parasympathetic fibers
pterygopalatine ganglion lacrimal gland
• Leaves the facial canal through the hiatus, runs forwards,
downward and inward in a furrow on the anterior
surface of the pyramid of the temporal bone.
• Leaves the cranial cavity through foramen lacerum after
joining the deeo petrosal nerve from the sympathetic
plexus of the internal carotid artery
• Sup and deep petrosal nerves form the pterygoid or the
vidian nerve pterygopalatine ganglion
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23. Nerve to stapedius muscle
• Arises opp. to the pyramid of the middle ear
• Supplies the stapedius muscle
• Stapedius muscle – dampening of excessive
vibrations of the stapes
• In paralysis- hyperacusis
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24. Chorda tympani
• Arises 6 mm above stylomastoid foramen
• Contains taste fibers and preganglionic
parasympathetic secretory fibers
• Enters tympanic cavity posterior wall in close
relation to tympanic membrane Leaves the middle
ear by passing though petrotympanic fissure Enters
infratemporal fossa joins lingual nerve
24

25. Extra-tympanic branches

26. Terminal branches
• At the stylomastoid foramen, the main trunk
enters the substance of the parotid gland.
• First separation into upper and lower division
usually occurs behind the mandible.
• The upper division- temporal, zygomatic and
upper buccal
• The lower division- lower buccal, mandibular
and cervical
26

27. 27
Temporal
• Emerge from the parotid
gland at its upper pole
slightly in front of the
superficial temporal artery
• Anterior temporal : frontalis,
superior part of orbicularis
oculi, corrugator supercilii,
procerus
• Posterior temporal : anterior
and superior auricular
muscles

28. Zygomatic
• Leave the parotid
gland on its
anterosuperior
border
• Crosses the body of
zygomatic bone
• Supply inferior part
of orbicularis oculi
28

29. Buccal
• Emerge at the anterior
border of parotid
• Upper buccal: muscles
of upper lip and the
muscles of the nose
• Lower buccal :
buccinator and risorius
• Orbicularis oris
29

30. Marginal mandibular
• Runs parallel to lower
border of the mandible
• Cross facial vein and facial
artery
• Supplies muscles of lower
lip (depressor anguli oris
and depressor labii
inferioris) and mental
muscles 30

31. Cervical
• Leaves parotid gland
at or slightly above its
inferior pole
• Runs downward and
anteriorly
• Supplies platysma
31

32. Internal acoustic meatus Vestibulocochlear nerve
Geniculate ganglion A. Greater petrosal nerve
B. Lesser petrosal nerve
C. External petrosal nerve
Facial canal Vagus nerve
Stylomastoid foramen IX & X cranial nerve
Greater auricular nerve
Auriculotemporal nerve
Behind ear Lesser occipital
Face V nerve
Neck Transverse cutaneous nerve
Branches of Communication