Facial nerve

FACIAL NERVE
Dr. Kathirvel Gopalakrishnan
M.D.S (OMFS)

Contents
Nerve - Introduction
Cranial nerve
Facial nerve – Introduction
Embryology
Components and functions
Nuclei
Course
Ganglion
Branches and distribution
Applied aspects

INTRODUCTION:
A nervous system - an organized group of cells (neurons), specialized for the
conduction of an impulse to and from different parts of its body

NEURON – PARTS AND FUNCTIONS

FACIAL NERVE
Introduction:
• 7th cranial nerve
• Mixed nerve – Predominantly motor
Facial nerve: embryology and anatomy of its nucleus; MOJ Anat & Physiol. 2018;5(3):164‒166

Embryology:
Develops from the second branchial arch
and supply all the elements that derive from it
3rd week
of IUL
Facio-acoustic primordium
appears
4th week
of IUL
1st branch appears in rostral
aspect of embryo
5th week
of IUL
Nervus intermedius becomes
evident
4th week

7th
week
7th week of
IUL
Chorda tympani derived
Joins lingual nerve
Middle of 7th week, trunk
bifurcates into
temporofacial and
cervicofacial branches
End of 7th week, temporal,
zygomatic, buccal, marginal
mandibular and cervical
regions are recognized
clearly
7 ½ week7th week end

8th week
of IUL
The cartilaginous capsule
forms a groove around
• Facial nerve
• Stapedial artery and
• Stapes muscle.
This groove will become the
facial canal
12th week
of IUL
All the muscles of the face
are formed and all are
innervated by one of the
branches of the facial nerve

21st week of IUL The ossification of the facial canal begins,
which will only end when the collateral
branches of the facial nerve are found in their
definitive location
End of pregnancy The tympanic bone and the mastoid process are
not fully developed, so the petrous portion of
the facial nerve does not exist and will not be
formed until 4 years of age

Component Function
General visceral efferent Preganglionic parasympathetic innervation of
sublingual/submandibular gland, lacrimal gland,
nasal mucosa/mucous membrane
Special visceral efferent Motor innervation of muscles of facial
expression, stylohyoid, stapedius, posterior belly
of digastric
General somatic afferent Provides sensory input from the auricular concha,
portions of external auditory canal and tympanic
membrane
Special visceral afferent Provides taste from the anterior two-thirds of the
tongue via the chorda tympani nerve
Facial Nerve and Parotid Gland Anatomy Amit Kochhar, MDa , Babak Larian, MDa,b , Babak Azizzadeh, MDa,b, ;
Otolaryngol Clin N Am 49 (2016) 273–284

NUCLEI
Facial nerve
 Motor
Nervus Intermedius
 General sensory
 Special sensory
 Superior salivatory
 Lacrimal

Origin
The facial nerve arises from pons and exits the
brain stem from its ventrolateral surface
Consists of two parts:
• Facial nerve
• Nervus Intermedius
The Facial nerve - motor component and very
small general somatic afferent component
The nervus intermedius- sensory and
parasympathetic visceromotor components.
Neuroanatomy, Cranial Nerve 7 (Facial) ; Dominika Dulak; Imama A. Naqvi. ; Stat pearls publishing, 2020 Jan

Course
Divided based on its relation to the cranium and the temporal bone into
• Intracranial
• Intratemporal
• Extratemporal
Intracranial part:
Two roots, Facial nerve motor root
and nervus intermedius arises from the
pons at a lateral aspect
It runs along with the
vestibulocochlear nerve and enters
internal acoustic meatus

Intratemporal part:
The Facial nerve and nervus
intermedius travel through the internal
acoustic meatus, a 1cm long opening in
the petrous part of the temporal bone.
Enters into the facial canal, a ‘Z’
shaped structure which consists of
 Meatal segment
 Labyrinthine segment
 Tympanic segment
 Mastoid segment
Facial Nerve Anatomy and Clinical Applications; Sinali O. Seneviratne; Bhupendra C. Patel; StatPearls Publishing LLC; 2020

Meatal segment:
The superior quadrant of the internal
acoustic meatus.
Labyrinthine segment:
•Facial nerve and nervus intermedius
fuse to form the geniculate ganglion
•Greater petrosal nerve –
parasympathetic fibres to mucous
glands and lacrimal gland.

Tympanic segment:
Runs in the medial wall of the
middle ear cavity
Mastoid segment:
•Nerve to stapedius – motor fibres to
stapedius muscle of the middle ear.
•Chorda tympani – special sensory
fibres to the anterior 2/3 tongue and
parasympathetic fibres to the
submandibular and sublingual glands.

Extratemporal parts:
Leaves the cranium through the
stylomastoid foramen, located just
posterior to the styloid process of the
temporal bone.
As it exits, it gives the first branch
posterior auricular supplying to the
pinna of the ear and external auditory
meatus
Then it gives branches to the posterior
belly of digastric, stylohyoid

Divides at the end of the posterior
edge of the parotid gland into the
terminal branches into two trunks:
• Temporofacial trunk
• Cervicofacial trunk
•Temporal branch – innervating the
frontalis and orbicularis oculi muscles
and the muscles in the upper part of
the face
•Zygomatic branch – innervating the
middle part of the face

•Buccal branch – innervating the
cheek muscles, including the
buccinator muscle
•Marginal mandibular branch –
innervating muscles of the lower
part of the face
•Cervical branch – innervating the
muscles below the chin and the
platysma muscle

Classification of Terminal branching pattern of facial nerve by Davis et al (1956)

Classification of Terminal branching pattern of facial nerve by Katz et al (1987)
TYPE 1a TYPE 1b TYPE 2 TYPE 3a TYPE 3b
TYPE 3cTYPE 5TYPE 4bTYPE 4a TYPE 4bTYPE 4a

Classification of Terminal branching pattern of facial nerve by Kopuz et al (1994)

Branch of facial nerve Distribution
Within facial canal
Greater Petrosal Nerve Enters foramen lacerum and joins deep
petrosal nerve to form Nerve of Pterygoid
canal.
It then relays with Pterygopalatine ganglion
and supply lacrimal gland and mucosal
gland of nose and palate
Chorda tympani Nerve Passes through Pterygopalatine fissure and
joins with Lingual nerve
Taste sensation from anterior 2/3rd of the
tongue
Nerve to stapedius Stapedius muscle

After exiting Stylomastoid foramen
Posterior Auricular nerve Posterior auricular, Superior auricular,
Occipital belly of occipitofrontalis
Nerve to digastric Posterior belly of digastric muscle
Nerve to stylohyoid Stylohyoid
Terminal Branches
Temporal Anterior auricular, Superior auricular, Part of
frontalis, upper part of Orbicularis oculi
Zygomatic Lower part of Orbicularis oculi
Buccal Buccinator, Orbicularis oris, Muscles of upper lip
Marginal mandibular Mentalis, Orbicularis oris, Muscles of lower lip
Cervical Platysma

Ganglia:
Geniculate Ganglion:
• Sensory ganglion
• Located on the first bend of
facial nerve in relation to
medial wall of ear in facial
canal
• Taste sensation to anterior
2/3rd of tongue
B.D CHAURASIA’S HUMAN ANATOMY VOLUME 3

Submandibular Ganglion:
• Parasympathetic ganglion
• Secretomotor fibres for submandibular and sublingual gland relay with
this ganglion
• Preganglionic fibres from chorda tympani nerve

Pterygopalatine Ganglion
• Largest Parasympathetic ganglion
• Secretomotor fibres for lacrimal gland relay with this ganglion

BRANCHES AND DISTRIBUTION

Lesion:
• Upper motor neuron lesion
• Lower motor neuron lesion
The neurons to the upper face receive
bilateral UMN innervation
The neurons to the lower face receive
UMN from the contralateral motor cortex
Facial Palsy, a Disorder Belonging to Influential Neurological Dynasty: Review of Literature Ujwala R. Newadkar, Lalit
Chaudhari, Yogita K. Khalekar; North American Journal of Medical Sciences; 2016

Upper motor lesion:
Causes unilateral facial palsy with some sparing of the frontalis and orbicularis
oculi muscles because of the bilateral cortical representation.
Furthermore, although voluntary facial movements are impaired, the face may still
move with emotional responses, for example on laughing.
Paresis of the ipsilateral arm (monoparesis) or arm and leg (hemiparesis), or
dysphasia may be associated because of more extensive cerebrocortical damage.

Lower motor neuron
Characterized by unilateral paralysis of all muscles of facial expression for both
voluntary and emotional responses.
The forehead is unfurrowed and the patient is unable to close the eye on that side.

Bells palsy:
• Bell’s palsy is a common cranial neuropathy causing
acute unilateral lower motor neuron facial paralysis.
• Demonstrated by Sir Charles Bell in 1821
Etiology:
Herpes simplex virus
Trauma
Infection
Nerve compression
Idiopathic
Bell’s palsy: aetiology, clinical features and multidisciplinary care Timothy J Eviston, Glen R Croxson, Peter G E
Kennedy, Tessa Hadlock, Arun V Krishnan; J Neurol Neurosurg Psychiatry; April 2015.

Bell’s palsy: aetiology, clinical features and multidisciplinary care Timothy J Eviston, Glen R Croxson, Peter G E
Kennedy, Tessa Hadlock, Arun V Krishnan; J Neurol Neurosurg Psychiatry; April 2015.
Clinical features:
1. Unilateral involvement
2. Absence of wrinkles in forehead
3. Loss of blinking reflex
4. Inability to close the eye, wink or smile
5. Impossible to whistle
6. Obliteration of nasolabial fold
7. Drooping of corner of the mouth
6. Mask like appearance of face
7. Bell’s Sign: In an attempt to close the eyelid, the eyeball turns
upward so that the pupil is covered and only the white sclera is visible.

•Blink test (corneal reflex):
When tapping on the patient’s glabella, a
suspension in blinking will occur on the affected side
•Schirmer test (assessing lacrimation of the
lacrimal gland):
Lacrimation will be decreased by 75%
compared to the normal side using a folded strip of
blotting paper in the lower conjunctival fornix.
Facial nerve palsy; Nathan R. Walker; Rakesh K. Mistry; Thomas Mazzoni; StatPearls Publishing; Jan 2020.

•Stapedial test:
This involuntary reaction in response to high-intensity sound stimuli causes
contraction of the stapedius muscle and gets mediated by the facial nerve.
Testing of the stapedius reflex can be performed using tympanometry.

•Salivary Test:
Salivation rate is assessed from a submandibular
duct following stimulation with a 6% citric acid
solution.
If positive, there will be a reduction in salivation
by 25% at the affected side and indicate a lesion at the
chorda tympani.
•Taste test:
Salt, sweet, sour and bitter tastes applied along
the lateral aspects of the anterior two-thirds of the
tongue.
A positive result will indicate a lesion at the
chorda tympani.

Approaches to Grading Facial Nerve Function Michael J. Brenner, M.D and J. Gail Neely, M.D., F.A.C.S

Management:
Medical management:
Additional measures include eye protection, physiotherapy, acupuncture,
botulinum toxin. An eye patch is of value to protect the cornea.

Surgical management:

Ramsay hunt syndrome:
Peripheral facial nerve palsy
accompanied by an erythematous vesicular
rash on the ear or in the mouth.
Varicella zoster virus (VZV) causes
Ramsay Hunt syndrome.
Bell’s palsy is significantly associated
with herpes simplex virus (HSV)
Ramsay Hunt syndrome C J Sweeney, D H Gilden; Jounal of Neurology, Neurosurgery and Psychiatry 2001

Signs and Symptoms:
Facial paralysis
Rash – Ear, Palate and tongue
Tinnitus
Hearing loss
Nausea
Vomiting
Vertigo
Nystagmus.
Due to close proximity of the geniculate
ganglion to the vestibulocochlear nerve
within the bony facial canal.

Management:
Medication Dose
Famciclovir 500 mg, three times daily for 7–10 days
Acyclovir 800 mg, five times daily for 7-10 days
Oral prednisone 60 mg daily for 3–5 days

Melkersson Rosenthal syndrome:
•Also known as Orofacial Granulomatosis
• Triad:
Relapsing facial paralysis
Persistent or recurrent orofacial edema
Fissured tongue
Rare to observe all aspects of the triad at the same time.
Melkersson–Rosenthal syndrome: a case report of a rare disease with overlapping features; Mauro Cancian, Stefano Giovannini, Annalisa
Angelini, Marny Fedrigo, Raffaele Bendo, Riccardo Senter & Stefano Sivolella; Allergy, Asthma and clinical immunology; 2019

Anatomical considerations:
Safe dissection:
Frontal Branch:
When using a lateral or superior approach,
staying right on or deep to the superficial leaf of
the deep temporal fascia is a safe plane of
dissection.
Anatomical Considerations to Prevent Facial Nerve Injury; Jason Roostaeian, Rod J. Rohrich, James M. Stuzin; The
American Society of Plastic Surgeons; 2015

Identification of facial nerve:

Facial nerve

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