Anatomy of facial nerve

1. FACIAL NERVE

2. CONTENTS
1. Introduction
2. Nuclei of origin
3. Course & Relations
4. Branches of facial nerve
5. Ganglia associated with facial nerve
6. Testing of facial nerve
7. Identification of facial nerve
8. Nerve injury

3. Introduction
• The Facial nerve is the 7th of twelve paired
cranial nerves.
• It is a mixed nerve with motor and sensory roots.
• It also supplies pre-ganglionic
parasympathetic fibres to several
head and neck ganglia

4. Nuclei of Origin
1. Motor nucleus
2. Superior salivatory nucleus
3. Nucleus of tractus solitarius

5. The facial nerve is formed mainly of two parts:
• 1- Facial nerve proper (motor): arising from facial
motor nucleus in pons.
• 2- Nervus intermedius: it is the sensory root of facial
lies position between the facial proper and
vestibulcochlear nerve in the pontocerebellar angle.
Carrying para-sympathetic fibers (from superior salivary
nucleus) and taste fibers ( to the solitary nucleus).

6. Course & Relations
• I- Intracranial (intrapetrosal) course
• II- Extracranial course

13. Branches
1. Greater superficial petrosal – arises from the geniculate ganglion.
2. Branches within the facial canal:
• i) nerve to stapedius
• ii) Chorda tympani
3. After exit from stylomastoid foramen:
• i) Posterior auricular
• ii) Nerve to posterior belly of digastric
• iii) Nerve to stylohyoid.
4. On the face - Five major branches:
• i) Temporal
• ii) Zygomatic
• iii) Buccal
• iv) Marginal mandibular
• v) Cervical

14. Ganglia associated with facial nerve
• Geniculate ganglion
• Submandibular ganglion
• Pterygopalatine ganglion

15. 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

16. 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

17. 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

18. Facial Nerve blood supply
• The facial nerve gets it’s blood supply from 5 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
 Posterior auricular artery supplies the facial nerve at & distal to
stylomastoid foramen
• Venous drainage parallels the arterial blood supply

19. Testing of Facial Nerve Branches
• Temporal branches -patient is asked to frown and
wrinkle his or her forehead.
• Zygomatic branches -the patient is asked to close
their eyes tightly
• Buccal branches -puff up cheeks (buccinator) smile
and show teeth (orbicularis oris) tap with finger over
each cheek to detect ease of air expulsion on the
affected side

20. Applied Surgical anatomy of Facial Nerve in
Oral & Maxillofacial Surgery
After exiting the stylomastoid foramen, which is situated
posterolateral to stylomastoid process, the nerve enters
the substance of parotid gland where it divides into its
upper and lower divisions just posterior to the mandible
The approximate distance from the lowest point of the
external bony auditory meatus to the bifurcation of the
facial nerve is 2.3cm
Posterior to the parotid gland,the nerve is atleast 2cm
deep into the skin surface,from this point the two branches
curve around the posterior mandible,where they form
plexus between the parotid gland and the masseter
muscle

21. Temporal branch
• It exits the parotid gland anterior to superficial
temporal artery
During an open approach to the TMJ, violation
of this branch is possible

22. Zygomatic Branch :
• Its course is antero superior crossing the
zygomatic bone
Inadvertent damage may occur to this nerve
during open reduction of zygomatic arch or
with the use of a byrd screw or zygomatic
hook during closed approaches

23. The surgeon must be mindful of the facial nerves
intimate involvement with the TMJ, specially
when performing surgical approaches to the joint.
The temporal and zygomatic branches are at
increased risk during pre auricular approach and
the marginal mandibular branch during
submandibular approach
The intra oral approach to the TMJ has minimal
risk to the branches of facial nerve which is its
major advantage

24. Buccal Branch:
• It runs almost horizontally and will often
divide into separate branch above and below
parotid duct as it runs anteriorly
Injury is possible in association with soft
tissue trauma to the cheek region

25. Marginal mandibular branch:
• It extends anteriorly and inferiorly within the substance of parotid
gland, there may be two or three branches of this nerve.
These branches run anteriorly parallel to inferior border of
mandible and in some cases the course of the nerve is above the
inferior border.
In essentially all cases the nerve is located above the inferior border
of mandible beyond the facial artery. The marginal mandibular
branch is an important structure encountered at the inferior border
of the mandible just beneath the platysma muscle fibres during an
open approach to the mandibular angle and body area.
• For this reason, an initial incision made approximately 1 to 1.5cm
below the inferior border which prevents direct exposure or trauma
to the nerve

26. Cervical Branch:
• The cervical branch exits the parotid gland
above its inferior pole and runs downwards
underneath the platysma muscle

27. Identification of Facial Nerve
3 surgical maneuvers used to identify
nerve trunk
A. Blood free plane in front of
external acoustic meatus
B. Exposure of anterior border of
SCM below insertion into
mastoid process
C. Peripheral identification of
terminal branch of facial nerve
(marginal mandibular branch)

29. Supra
nuclear type:
• Paralysis of lower part of face (opposite side)
• Normal taste and saliva secretion
• Stapedius not paralysed
Nuclear
type:
• Paralysis of facial muscle (same side)
• Paralysis of lateral rectus
• Internal strabismus

30. Peripheral
lesion
At internal acoustic
meatusa
Paralysis of secretomotor
fibers
Hyper acusis
Loss of corneal reflex
Taste fibers unaffected
Facial expression and
movements paralysed
Injury distal to
geniculate ganglion
Complete motor paralysis
(same side)
No hyper acusis
Loss of corneal reflex
Taste fibers affected
Facial expression and
movements paralysed
Pronounced reaction of
degeneration
Injury at
stylomastoid foramen
Bell’s Palsy

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