The document describes the anatomy and clinical considerations related to the facial nerve. It begins by detailing the various branches of the facial nerve and their course through the parotid gland and across the face. It then discusses landmarks used during surgery to identify the nerve. Several causes of facial nerve paralysis are listed including Bell's palsy, Ramsay Hunt syndrome, Melkersson-Rosenthal syndrome, and complications from procedures like IANB. Classification systems for nerve injuries are also summarized.

2.  The main trunk of the nerve exits the stylomastoid
foramen and immediately enters the parotid gland.
 The most consistent and reliable landmark for
identification of the facial nerve is the tympanomastoid
suture.
 This suture line between the tympanic and mastoid
portions of the temporal bone points to the
stylomastoid foramen, which is 6 to 8 mm beneath
(medial to) the “drop-off” point of the tympanomastoid
suture (Tabb and Tannehill, 1973).
 The main trunk can generally be found approximately
midway between the cartilaginous pointer of the
external auditory canal and the posterior belly of the
digastric muscle, where it attaches to the mastoid tip.
 The styloid process is deep to the main trunk.

3.  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
2.3 cm (1.5-2.8)
 Length of facial nerve trunk is
1.3 cm.
 Posterior to the parotid
gland,the nerve is at least 2cm
deep into the skin surface.

4.  The terminal branches of facial nerve then
spread in a fan like fashion as five separate
nerves

5. Temporal branch :
 The temporal branches of the facial nerve
are often called the frontal branches when
they reach the supraciliary region.
 Nerve injury is revealed by the inability to
raise the eyebrow or wrinkle the forehead.
 The temporal branch or branches of the
facial nerve leave the parotid gland
immediately inferior to the zygomatic arch.

6.  The general course is
from a point 0.5 cm
below the tragus to a
point 1.5 cm above the
lateral eyebrow .
 It crosses superficial to
the zygomatic arch at
an average distance of
2 cm anterior to the
anterior concavity of the
external auditory canal,
but in some cases it is
as near as 0.8 cm or as
far as 3.5 cm anterior to
the external auditory
canal.

7.  As the temporal branch
crosses the lateral surface of
the arch, it courses along the
undersurface of the
temporoparietal fascia,
between it and the fusion of
periosteum of the zygomatic
arch, the superficial layer of
temporalisfascia, and the
subgaleal fascia .
 As the nerve courses
anterosuperiorly toward the
frontalis muscle, it lies on the
undersurface of the
temporoparietal fascia and
enters the frontalis muscle no
more than 2 cm above the
level of the superior orbital
rim.

8. • Anatomic dissection showing
the position of the temporal
branch of the facial nerve in
relation to the temporoparietal
fascia and zygomatic arch.
• The temporoparietal fascia is
retracted inferiorly.
• The temporal branch of the
facial nerve courses on its
deep surface (or within the
layer of fascia) anteriorly and
superiorly (dashed lines),
between the temporoparietal
fascia and the point of fusion
of the superficial layer of the
temporalis fascia with the
periosteum of the zygomatic
arch.

9. 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
 The mean horizontal distance of the zygomatic
branch (the most upper one) as it emerged from
the anterior border of the parotid gland and the
tragus was 30.71 mm, whereas the mean
vertical distance of the zygomatic branch from
the midpoint between the tragus and the lateral
palpebral commissure was 19.29 mm.

10. 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
 Two studies evaluating landmarks for identification
of the buccal branch of the facial nerve (BN) were
found to be suitable for review.
 Both studies focused on the parotid duct as a
landmark for localization of the BN, itself a mobile
soft tissue structure.
 Pogrel et al. (1996) examined the course of the BN
in 20 cadaveric facial halves and noted the position
of the BN relative to the parotid duct.

11.  The BN coursed a distance of 2.3 mm from the point of
emergence at the anterior edge of the parotid gland to
the point at which it crossed the duct.
 When inferior to the duct, a vertical distance of
5.43±3.65mm was measured from the duct to the BN.
 While Saylam et al (2006)documented the position of
the BN relative to the parotid duct
 Only 21/66 (35%) of specimens were observed to have
branches passing inferior to the duct, 16.78±13.20mm
from point of emergence.
 In 25% of specimens, the BN coursed superior to the
duct at a distance of 18.18±5.04mm from the anterior
edge of the parotid gland.

12. 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.
 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.

13.  The marginal mandibular branch or branches, which
supplymotor fibers to the facial muscles in the lower lip and chin,
represent the most important anatomic hazard while performing
the submandibular approach to the mandible.
 Studies have shown that the nerve passes below the inferior
border of the mandible only in very few individuals
 In the Dingman and Grabb classic dissection of 100 facial
halves, the marginal mandibular branch was almost 1 cm below
the inferior border in 19% of the specimens
 Another important finding of the study by Dingman and Grabb
was that only 21% of the individuals had a single marginal
mandibular branch between the angle of the mandible and the
facial vessels , 67% had two branches 9% had three branches,
and 3% had four.

14.  Ziarah and Atkinson found more individuals in whom the
marginal mandibular branch passed below the inferior
border.
 In 53% of 76 facial halves, they found the marginal
mandibular branch passing below the inferior border
before reaching the facial vessels, and in 6%, the nerve
continued for a further distance of almost 1.5 cm before
turning upward and crossing the mandible.
 The farthest distance between a marginal mandibular
branch and the inferior border of the mandible was 1.2 cm.
 In view of these findings, most surgeons recommend that
the incision and deeper dissection be at least 1.5 cm
below the inferior border of the mandible.

15. Examples of the variation in facial
nerve anatomy. Three branches of the
marginal
mandibular nerve are shown coursing
anteriorly (m) while the cervical
branch is shown coursing inferiorly
(c).
In this photograph, the marginal
mandibular branch (m) is seen
coursing deep to the retromandibular
vein (v).

16. Cervical Branch:
 The cervical branch exits the parotid gland
above its inferior pole and runs downwards
underneath the platysma muscle.
 The gonion and angle of mandible may be
used as reliable landmarks during
preoperative planning to identify or avoid
injury to the cervical branch during
retromandibular and submandibular
approaches.

17. 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)

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 Semicircular
Canal: nerve runs
below
4. Oval window: nerve runs above
5. Pyramid: nerve runs behind
6. Tympanomastoid suture: nerve runs
behind
7. Digastric ridge: nerve at anterior end

19. For parotid surgery:
 Trunk of facial nerve is deep in location (average
3.0- 3.5 cm beneath the skin surface)
 It consistently emerges from the stylomastoid
foramen between four well known landmarks
1. The palpable bony transverse process of atlas
inferiorly
2. The palpable bony external cartilageous meatus
superiorly.
3. The palpable bony posterior border of ramus
anteriorly
4. Mastoid tip posteriorly.

20.  The surgeon can easily pin point its
anticipated location by advancing finger
anteriorly along the mastoid tip until it falls
into a hollow below the cartilageous meatus
just posterior to ramus of mandible

26.  Facial nerve paralysis is a common problem
that involves paralysis of any structures
innervated by facial nerve.
 Pathway of facial nerve is long and
convoluted ,so there are a number of causes
that result in facial paralysis.
 Facial nerve paralysis classified as
1. Supranuclear lesions(UMN lesion)
2. Infranuclear lesions(LMN lesion)

30. CONGENITAL
• Moebius Syndrome
• Myotonic dystrophy
• Melkersson Rosenthal syndrome
• Congenital Cholesteatoma
• Birth injuries
• Osteopetrosis
NEUROLOGIC
• Myasthenia Gravis
• Multiple Sclerosis
• Guillain Barre syndrome

31. NEOPLASTIC
• Facial nerve tumours
• Glomus tumours
• Meningiomas, acoustic neuroma
• Parotid tumours
• Temporal bone/external auditory meatus
tumours
INFECTIONS
• Otitis media, mastoiditis
• Bacterial causes
• Viral causes

32.  Two acceptable classification schemes used
to describe the histologic changes that occur
following nerve injury.

33. 1. Seddons classification
• Neuropraxia
• Axonotmesis
• Neurotmesis
2.Sunderland classification
• 1st degree( type I ,II,III)
• 2nd degree
• 3rd degree
• 4th degree
• 5th degree

34. Neuropraxia:
• Epineurium& endoneurium intact but nerve is just
compressed
• No axonal degeneration distal to site
• Temporary conduction block
• No surgical intervention
Axonotmesis: (prolonged conduction block)
• Loss of continuity of some axons(axonal degeneration)
• Distal to site, WALLERIAN DEGENERATION occurs
• After 3 months, initial signs of recovery
• Wallerian degeneration (when a nerve is cut or crushed
the part of axon distal to injury degenerates).

35. Neurotmesis (total permanent conduction block)
• Complete severance of all layers of nerve
• Distal to injury wallerian degeneration occurs
• Space between proximal & distal filled by scar
tissue
• Surgical intervention must

38.  It is defined as an idiopathic paresis or
paralysis of the facial nerve of sudden onset.
 The name was ascribed to SIR CHARLES
BELL, who in 1821demonstrated the
separation of motor and sensory innervation
of face.

39.  Idiopathic
 autoimmune response
 Viral hypothesis
 Ischemic hypothesis: factors producing
Vasospasm
1. Cold
2. Anoxia
3. Injury
4. Toxicity
5. Allergic

40.  Main cause of Bell's palsy is latent herpes
viruses
 (herpes simplex virus type 1 and herpes
zoster virus),which are reactivated from
cranial nerve ganglia
 Polymerase chain reaction techniques
have isolated herpes virus DNA from the
facial nerve during acute palsy

41.  Inflammation of the nerve initially results in a
reversible neurapraxia
 Herpes zoster virus shows more
aggressive biological behavior than herpes
simplex virustype1
 Bell's phenomenon is the upward
diversion of the eye ball on attempted
closure of the lid is seen when eye closure is
incomplete.

42.  INCIDENCE-15-40 cases per 1 lakh cases
 SEX PREDILECTION- women more affected
than men.
 3.3 more times common in pregnancy and in
the third trimester.
 AGE- can occur at any age, common in middle
aged people.
 SIDE INVOLVMENT- can be equally seen,
usually unilateral.

43.  Unilateral involvement
 Inability to smile, close eye or
raise eyebrow
 Whistling impossible
 Drooping of corner of the
mouth
 Inability to close eyelid (Bell’s
sign)
 Inability to wrinkle forehead
 Loss of blinking reflex
 Slurred speech
 Mask like appearance of face
 Loss/ alteration of taste

44.  Partial paralysis always resolves completely
within a few weeks.
 Recovery from complete paralysis takes
longer (months) and is complete in only
about 60-70% of cases.
 Approximately 15% of patients are left with
troublesome residual palsy and or
synkinesis( simultaneous movements ).

46. o James Ramsay hunt (1907)
o Caused by varicella zoster
o Infection along facial nerve near inner ear
o Syndrome occurs when geniculate ganglion is involved due to
reactivation
o Classical triad:
1. Ipsilateral facial paralysis
2. Ear pain/hearing loss
3. Vesicles in pinna
o Sensation of spinning
o tinnitus (is the perception
of noise or ringing in the ears)

48.  Also known as orofacial
granulomatosis
 Idiopathic Neurological
disorder
 Non tender persistent
swelling of one or both
lip
 Facial paralysis
 Lingua plicata
(fissured tongue)

49.  Otitis media is an infection in the middle
ear, which can spread to the facial nerve
and inflame it, causing compression of the
nerve in its canal.

50. Moebius syndrome (congenital
facial diplegia)
 Facial Nerve absent / smaller
 Congenital Extra ocular muscle &
facial palsy
 Described by Moebius(1888)
 Rare neurological disorder
 Congenital defect -Paralysis of VII
and VI nerves
 Mask like face –expressionless
 Unable to close eyes-corneal
ulcerations
 Strabismus (a condition in which
the eyes do not properly align
with each other when looking at
an object).

51.  first Described by Jean landry(1800s)
 Discovered by Jean Barre and Georges
Guillain(1916)
 Inflammatory demyelinating polyneuropathy
affecting peripheral nerves including VII nerve
causing facial palsy
 Treated by IVIG(Intravenous Immunoglobulin
Treatment )& Plasma exchange

53.  Encountered during IANB
 Due to injection of LA into parotid gland if
needle injected too backwards
 Temporary paralysis of facial nerve
 Effect wears off over a period of time(<3Hrs)
during which eye needs to be protected(eye
patch).

54.  Unilateral facial paralysis involving only the
lower lip and congenital heart disease
 The facial paralysis in these patients
involves only those muscles concerned with
pulling the lower lip downwards and
outwards.
 These are the mentalis, depressor labii
inferioris and depressor anguli oris muscles.

55.  All are supplied by the mandibular marginal
branch of the facial nerve.
 Lesions of this nerve have been recognized in
adults and children for many years
 The paralysis is only recognizable when the
patient talks, smiles or cries

56.  There is a set of typical symptoms within
Treacher Collins Syndrome
 The OMENS classification was developed as
a comprehensive and stage-based approach
to differentiate the diseases.
 O; orbital asymmetry
 M; mandibular hypoplasia
 E; auricular deformity
 N; nerve development and
 S; soft-tissue disease

57.  N0: No facial nerve involvement
 N1: Upper facial nerve involvement (temporal
or zygomatic branches)
 N2: Lower facial nerve involvement (buccal,
mandibular or cervical)
 N3: All branches affected

58.  It is a wide spectrum of congenital anomalies that
involves structures arising from the first and second
branchial arches.
 Features of hemi facial microsomia, anotia(absence of
the external ear), vertebral anomalies, congenital
facial nerve palsy.

59. Involuntary twitching of
facial muscles on one or
both sides
1. Hemifacial spasm- on
oneside due to irritation of
nerve at cerebellopontine
angle( microvascular
decompression, botulinum
toxin)
2. Blepharospasm- limited
to orbicularis oculi on both
sides(bot toxin into
periorbital muscles).

60.  References
 Grays anatomy 39th edition.
 Journal of oral and maxillofacial surgery
 Atlas of anatomy.
 Oral and maxillofacial trauma FONSECA 4th edition.
 Surgical approach to facial skeleton 2nd edition ESWARD
ELLIS III AND MICHEAL F.ZIDE.
 Dingman RO, Grabb WC. Surgical anatomy of the
mandibular ramus of the facial nerve based on the dissection
of 100 facial halves. Plast Reconstr Surg. 1962;29:266.
 Ziarah HA, Atkinson ME. The surgical anatomy of the
cervical distribution of the facial nerve. Br J Oral Maxillofac
Surg. 1981;19:159.
 Journal of Craniofacial Surgery: January 2006 - Volume 17 - Issue 1 -
p 50-53
 (PDF) Anatomic landmarks for localization of the branches of the facial
nerve. Available from:
https://www.researchgate.net/publication/259758680_Anatomic_landm
arks_for_localization_of_the_branches_of_the_facial_nerve [accessed
Jul 03 2018].