Surgical anatomy plastic surgery point of view

1. Facial Nerve Anatomy and
management of bells palsy
Moderarator: Dr Upendra Sharma
Presenters: Dr Meghna
Dr Shamendra

2. • Nuclei of origin
• Roots: Sensory root (nervous intermedius)
Motor root
• Course – Intracranial/Intrapetrous
part,Extracranial part.
• Branches – of Communication
of Distribution

3. Nuclei of Origin :
• Motor Nucleus :
Site: situated in reticular formation in caudal part
of pons below and in front of abducent nucleus.
At the cranial end of the abducent nucleus,the fibres
bend abruptly downwards and forwards forming an
internal genu (First genu)
And finally emerge at the lower border of the pons
through the motor root.

5. • Superior salivatory
nucleus:
situated dorsolateral to
caudal part of motor
nucleus
Gives origin to pre
ganglionic secreto
motor
fibres(parasympathetic)
which emerge through
the sensory root
Sensory Root =misnomer
(conveys secretomotor
fibres also)
• Upper part of the nucleus
of tractus solitarius :
acts as a afferent column
Recieves taste sensation
from ant 2/3 of the tongue
via corda tympani nerve
from soft palate through
greater petrosal nerve.

7. • Course :
Divided by stylomastoid foramen into
intracranial –intrapetrous part and extracranial
part.
Intracranial-intrapetrous part :
From the lower border of the pons , both roots of
facial nerve along with vestibulococlear nerve,
labyrinthine artery enter the internal acoustic
meatus .
Within the Internal acoustic meatus, motor root
lodges in a groove on the anterio superior
surface of vestibulo coclear nerve and sensory
root intervenes between them.

8. • At the bottom of the internal acoustic meatus, both
roots combine to form trunk and enter the bony
facial canal.
In the bony facial canal, nerve passes above the
vestibule of the inner ear , and reaches the medial
wall of epitympanic part of tympanic cavity.
In epitympanic part of tympanic cavity, facial nerve
bends backwards forming a 2nd genu (external
genu).
At the genu, facial nerve presents an asymetrical
swelling known as genicular ganglion(contains cell
bodies of pseudo unipolar sensory neurons).

11. • From the genu,facial nerve passses into another
bony canal above the promontary and fenestra
vestibuli and reaches the medial wall of the aditus
of mastoid antrum.Here nerve is related to bulging
of the lateral semicircular canal.
finally nerve passes vertically downwards along the
posterior wall of tympanic cavity and leaves the
temporal bone through stylomastoid foramen.

12. • Extracranial part :
After exit from stylomastoid foramen, it changes its
direction and passes forwards superficial to the styloid
process of the temporal bone and pierces the posterio
medial surface of the parotid gland.
With in the gland,nerve runs forwards for about 1 cm
superficial to retromandibular vein and ext carotid
artery and then divides into temporo facial and cervico
facial trunks.
Temporo facial trunk turns abruptly upwards and
subdivides into Temporal
Zygomatic branches.

13. • The Cervico facial branch passes downward and
forward and subdivides into Buccal ,
marginal mandibular
Cervical branches.
The five terminal branches radiate like goose feet
through the anterior border of the gland and
supply the facial muscles. Such branching pattern
is known as the pes anerinus.

14. Points of special importance :
• The stylomastoid foramen lies about 2 cm deep to
the middle of the anterior border of the mastoid
process.In the new born, stylomastoid foramen
lies at the surface of the mastoid bone ,since the
mastoid process grows about the 2nd year after
birth.Therefore , incisions behind the auricle are
taken carefully in a child in order to avoid injury to
facial nerve.

15. • Branches:
1) In the facial canal :
a) Nerve to stapedius : Hyperacusis
b) Chorda tympani nerve : Taste sensations,
Preganglionic secretomotor fibres to
submandibular and sublingual gland.
2) Below the stylomastoid foramen :
a)Posterior auricular nerve : passes behind
the auricle. Supplies intrinsic muscles on the
cranial surface of the auricle , auricularis
posterior and occipital belly of
occipitofrontalis.

16. b) Nerve to post belly of digastric
c) Nerve to the stylohyoid muscle
3) In the face:
5 terminal branches:
a) Temporal branch :consists of 3 or 4 branches. They
pass upwards and forwards in front of the auricle and
crosses over the zygomatic arch 3 to 5 cm from lateral
orbital margin. After that,they run deep to temporo
parietal fascia(sup temporal fascia).
Supplies ,
Auricularis anterior
Auricularis superior
Upper part of orbicularis occuli
Frontalis
Corrugator supercilli

18. b) Zygomatic branch :
consists of 5 to 8 branches with significant functional
overlap. Runs along the zygomatic arch and then deep to
parotid messeteric fascia in the same plane as that of
parotid duct.
Supplies lower part of orbicularis occuli.
c) Buccal branch :
Consists of superficial and deep parts.
Superficial branches : supply procerus
Deep branches : subdivide into upper and lower sets.
upper buccal : passes forwards above the parotid duct
and supply Zygomaticus major
Zygomaticus minor
Levator anguli oris
Levator labi superioris
Levator labi superioris alaeque nasi
Muscles of the nose –dialator naris,
Dialator septi

21. Lower buccal : passes below the parotid duct
Supplies Buccinator
Orbicularis oris .
d) Marginal mandibular branch : consists of 1 to 3
branches .appears first in the neck(2 cm below the
ramus) ,then curves upwards and forwards across
the lower border of the mandible at the anterio
inferior angle of the masseter
and appears in the face after crossing superficial
to facial artery and vein.
Supplies Risorius
Depressor angulli oris
Depressor labi inferioris
Mentalis

23. e) Cervical branch : consists of single branch.
comes out of apex of parotid gland and
appears in anterior triangle of neck and
Supplies Platysma by entering the muscle at
its cranial and middle 1/3rds.point of entry is
2-3 cm caudal to platysmal muscle branch of
facial artery.

24. Facial muscles responsible for facial
expression:
• Frowning : Corrugator supercilli forms vertical
wrinkles on forehead.Procerus forms transverse
wrinkles across the root of the nose.
• Surprise,horror, fright : Frontalis by elevation of
eyebrows and transverse wrinkles of the
forehead.
• Anger : Dialator nares , Depressor septi.They
dialate the anterior nasal apertures and
depressing the mobile part of the septum.

25. • Sadness : Levator anguli oris , Levator labi
superioris , zygomaticus minor by accentuating
the naso labial furrow.
Depressor anguli oris by drawing the angle of
the mouth downwards and laterally.
• Laughing : zygomaticus major which draws angle
of the mouth upwards and laterally.
• Irony : Depressor labi inferioris by drawing the
angle of mouth inferiorly and some what
laterallly.
.

26. • Grinning : Risorius by
retracting the angle of
mouth laterally

27. • Disdain : Mentalis , by
puckering the chin and
protruding the lower
lip.

28. Salient features about extra cranial facial
nerve :
• The five divisions of facial nerve are to some extent
artificial .
• There is no distinct seperation between zygomatic and
buccal branches
• As the branches exit from the parotid gland , there may be 8
to 15 branches making up to five divisions.
• Distal to parotid , there is significant arborization and
interconnection of these branches.
• There is significant functional overlap and frequent
duplication of branches providing same function.

29. • Each of the divisions consist of multiple branches
,except for cervical division which consists of single
branch.
• There are fewer crossover communications between
the frontal branches and marginal
mandibular branches. Hence,injuries to these nerves
are less likely to recover function in their respective
muscles

30. The branches of the
facial nerve can be
seen where they
exit from the anterior
margin of the parotid.
They have been
separated
from the surrounding
tissue in preparation
for stimulation and
functional
identification

31. Facial musculature:
• There are 18 paired muscles of the face, including
the orbicularis oris.
• Facial muscles are arranged in layers about the
mouth .
• The most superficial are the depressor anguli oris,
zygomaticus minor, and the orbicularis
oris.
The deepest layer consists of the buccinator,
mentalis,and the depressor anguli oris.

33. SMAS :
• Five layers of the face: Skin;
Subcutaneous fat
Superficial musculoaponeurotic system (SMAS)–
muscle layer;
Transparent fascia
Branches of the facial nerve.
• The muscles of facial expression are part of the
SMAS layer.
• In the temporal region, this layer is not muscular
but is fascial in quality and is represented by the
superficial temporal fascia (or temporoparietal)
fascia.

34. • The fourth layer = layer of areolar tissue.
• In the temporal area, this layer is known as the
innominate or subgaleal fascia.
In the cheek-parotid–masseteric fascia; and
Neck-superficial cervical fascia.
Once under the SMAS, the facial nerve branches can
be seen through this fourth layer.
• Though not totally accurate, galea–frontalis–
temporoparietal fascia–SMAS– orbicularis oculi–
platysma as a single layer,
• Similiarly , subgaleal fascia–innominate fascia
parotid/masseteric fascia–superficial cervical fascia
as a single layer.

35. The anatomic layers of the
face.
Although the quality of the
layers differs in various
areas of the face, the
arrangement of layers
is identical. The facial nerve
(cranial nerve [CN]
VII) branches innervate their
respective muscles via
their deep surfaces.

36. • Facial nerve branches travel deep to the SMAS
layer, but at some point these branches turn
superficially to innervate the overlying muscles .
• Ex : Any dissection in the sub-SMAS plane in the
cheek necessitates a change of surgical planes at
the zygomaticus major muscle to avoid
transection of the branch to this muscle. The
dissection plane changes from sub-SMAS to
subcutaneous by passing over the superficial
surface of the zygomaticus major ,thereby
preserving its innervation.