FACIAL NERVE AND IT'S APPLIED ANATOMY AND IT'S SIGNIFICANCE FOR A DENTIST ALONG WITH THE CAUTIONS TO AVOID AN IATROGENIC INJURY TO FACIAL NERVE AND THE MANAGEMENT OF A PATIENT OF FACIAL NERVE DISORDER DURING ENDODONTIC PROCEDURES

1. FACIAL NERVE
AND IT’S APPLIED
ASPECT IN DENTISTRY
PRACHI JHA
JR 1
DEPT. OF CONSERVATIVE DENTISTRY
AND ENDODONTICS

2. CONTENT
 CRANIAL NERVE
 INTRODUCTION TO FACIAL NERVE
 EMBYOLOGY
 FUNCTIONAL COMPONENT
 NUCLEUS
 FACIAL NERVE ROOTS
 COURSE
 BRANCHES AND DISTRIBUTION
 GANGLIA
 ARTERIAL SUPPLY AND VENOUS DRAINAGE
 CLINICAL EXAMINATION OF FACIAL NERVE
 APPLIED ANATOMY
 CHALLENGES FACED BY A DENTIST
 CASE REPORT

3. CRANIAL NERVES
 There are twelve pairs of cranial nerve.
 Their defining feature is that they exit the cranial cavity through foramen or fissures.
 All cranial nerve innervate structure in the head or neck.
 Parasympathetic fibres in the head are carried out of the brain as part of four cranial nerves –
• the oculomotor nerve (III),
• the facial nerve (VII),
• the glossopharyngeal nerve (IX),
• and the vagus nerve (X).
 The parasympathetic fibres in these nerves destined for target tissues in head and neck, are
distributed with branches of the trigeminal nerve.

5. INTRODUCTION TO FACIAL NERVE
It is the VII of the twelve paired cranial nerve.
Mixed Nerve (Sensory and Motor)
Sensory root is also known as Nervus Intermedius (Nerve of Wrisberg)
It emerges from lateral surface of brainstem between pons and medulla and supplies
the muscles of facial expressions.
Composed of approximately 10,000 neurons,
7,000 of which are myelinated and innervate facial muscle.
3,000 of the fibres are somatosensory.

6. EMBRYOLOGY
Derived from second branchial arch. (hyoid arch)
Facial nerve course, branching pattern and anatomical relationships are
established during 3rd month of prenatal life.
First identifiable tissue of facial nerve is seen at 3rd week of gestation-
facioacoustic primordium.
4th week - chorda tympani descends from the main branch.

7. 5th week - geniculate ganglion, nervous intermedius, greater petrosal
nerve appears.
7th week and 8th week- second branchial arch gives rise to muscle of
facial expression.
The nervus intermedius arise from the ganglion and passes to brainstem.
Motor root fibre pass mainly caudal to ganglion.
The nerve is not fully developed until 4 years of age.

8. FUNCTIONAL
COMPONENT
It carries the following fibres-
1. General Somatic Afferent Fibres (GSA)
Provides sensory input from part of external acoustic
meatus and deeper part of auricle.
Proprioceptive impulse from muscle of face travels
through branches of the trigeminal nerve to reach the
mesencephalic nucleus of the nerve.

9. 2. Special Visceral Afferent Fibres (SVA)
carry taste sensations from the palate and from anterior
two-third of the tongue except from the vallate papillae.
3. General Visceral Efferent Fibres (GVE)
Parasympathetic part of the autonomic division of the PNS
stimulate secretomotor activity in the lacrimal gland,
submandibular gland and sublingual gland, and glands in
the mucous membrane of nasal cavity, and hard and soft
palate.

10. 4. Special Visceral Efferent Fibres (SVE)
also known as branchial efferent
innervate the muscle of the face and scalp derived from
the second pharyngeal arch, and the stapedius, the
posterior belly of the digastric and the stylohyoid
muscle.
5. General Visceral Afferent Fibres (GVA)
carries afferent impulses from
• the lacrimal gland,
• submandibular gland and
• sublingual gland,
• glands of nose, hard and soft palate.

12. FACIAL NERVE NUCLEI
NUCLEI
MOTOR
NUCLEUS
SUPERIOR
SALIVATORY
NUCLEUS
NUCLEUS OF
TRACTUS
SOLITARIUS

14. 1) Motor nucleus:
It is located in lower pons below 4th ventricle
Divided into lateral, intermediate and medial leminsci
• Lateral portion supplies muscles around the mouth and buccinator
• Intermediate portion supplies muscles of upper face including orbicularis oculi.
• Medial portion supplies the stapedius, stylohyoid, posterior belly of digastric,
platysma and occipito frontalis.

15. 2) Nucleus of Tractus Solitarius:
It is located in Medulla Oblongata.
Special sensory nucleus brings sensations from the anterior 2/3rds of tongue and palate.
3) Superior Salivatory Nucleus:
It lies in Pons, dorsal to motor nucleus.
Preganglionic parasympathetic Secretomotor fibres to glands.
4) Upper part of nucleus of the spinal tract of the Trigeminal nerve:
Receives sensation of skin of EAM via auricular branch of vagus nerve.

16. ROOTS
MOTOR SENSORY

17. Facial nerve consists of a large motor and
a small sensory root ( the intermediate
nerve).
After entering the facial canal in petrous
temporal bone the two roots fuse and
form Facial nerve.

18. Near this point the nerve enlarges as geniculate ganglion.
At the geniculate ganglion the facial nerve turns and gives off the greater
petrosal nerve which carries GVE Fibres.
Facial nerve continues along the bony canal and gives off nerve to stapedius
and chorda tympani.
Chorda tympani carries taste fibres from anterior 2/3rd of tongue and
preganglionic parasympathetic fibres destined for submandibular gland.

19. 1. Facial nerve proper (motor):
• Arising from facial motor nucleus in pons.
• Supranuclear innervation to the muscles of facial expression arises from the lower
third of contralateral precentral gyrus in facial area of motor homunculus.
• Portion of nucleus that innervates the lower half to two thirds of the face has
predominantly contralateral supranuclear control;
• Portion that innervates upper third to half has bilateral control.

20. • Facial nucleus is special visceral efferent, or branchiomotor.
• It innervates the muscles of the second branchial arch
• Facial motor nucleus has lateral, medial, and dorsal sub nuclei, arranged in
columns.
• It exits the pons laterally at the pontomedullary junction, just caudal to the roots of
CN V between the olive and the inferior cerebellar peduncle.

21. 2. Nervus intermedius:
• Sensory and autonomic component of the facial nerve.
• Runs in a position intermediate between CN VII and VIII.
• At first external genu, NI fuses with the geniculate ganglion.
• Sensory cells located in the geniculate ganglion are general somatic afferent
(GSA) and special visceral afferent (SVA)
• Autonomic component of the NI consists of preganglionic general visceral
efferent parasympathetic fibres from superior salivatory and lacrimal nuclei.

22. COURSE
The path of facial nerve can be divided into six segments.
1) Intracranial segment:
Motor part arises from the branchiomotor nucleus, sensory and parasympathetic
parts from sensory nucleus and superior salivatory nucleus.
From the brain stem, the motor and sensory parts of the facial nerve join together
and traverse the posterior cranial fossa before entering the petrous temporal
bone via the internal auditory meatus.

23. 2) Meatal segment:
Enters the petrous temporal bone via internal auditory meatus.
Upon exiting the internal auditory meatus, the nerve then runs a tortuous course
through the facial canal, which is divided into the labyrinthine, tympanic, and
mastoid segments.
3) Labyrinthine segment:
The labyrinthine segment is very short, and ends where the facial nerve forms a
bend known as the geniculum of the facial nerve, which contains the geniculate
ganglion for sensory nerve bodies.

24. 4) Tympanic segment:
Facial nerve runs through the tympanic cavity medial to
incus.
5) Mastoid segment:
The pyramidal eminence is the second bend in the facial
nerve, where the nerve runs downward as the mastoid
segment.
In the temporal part of the facial canal, the nerve gives rise
to the nerve to the stapedius and chorda tympani.
MASTOID SEGMENT

25. The chorda tympani supplies taste fibres to the anterior two thirds of the tongue, and
also synapses with the submandibular ganglion.
Postsynaptic fibres from the submandibular ganglion supply the sublingual and
submandibular glands.
6) Extratemporal segment:
Emerges out from stylomastoid foramen and gives five terminal branches.

26. BRANCHES AND
DISTRIBUTION
A) Within the facial canal
1.Greater petrosal nerve:
Arises at the superior salivatory nucleus of the pons
Carries preganglionic parasympathetic fibres to the lacrimal, nasal and palatine glands.
Also provides parasympathetic innervation to the sphenoid sinus, frontal sinus, maxillary
sinus, ethmoid sinus and nasal cavity.
Also includes taste fibres for palate via lesser palatine nerve and greater palatine nerve.

27. 2. The nerve to the Stapedius muscle :
Provides motor innervation to stapedius muscle in the middle ear.
3. The Chorda tympani:
 Parasympathetic innervation to submandibular gland.
 Parasympathetic innervation to sublingual gland.
 Special sensory taste fibres for the anterior 2/3 of the tongue.

28. B) As it exit from the stylomastoid foramen:
1.The posterior auricular nerve:
Supplies auricularis posterior, occipitalis, intrinsic muscles on the back of the
auricle.
2. The nerve to the posterior belly of digastric:
supplies posterior belly of digastric.
3. The nerve to the stylohyoid muscle
supplies the stylohyoid muscle.

29. C) Terminal branches within the parotid gland
1.The Temporal nerve:
Comes out through the upper pole of parotid gland
Cross zygomatic arch
Muscles supplied –
• Auricularis anterior & superior
• Frontalis
• Corrugator supercilii
• Procerus
• Upper orbicularis oculi
Action – Raising eyebrows

30. 2. The Zygomatic nerve:
Also called Upper Zygomatic
Cross Zygomatic bone
Muscles supplied –
Lower Orbicularis oculi
Action – Tight shutting of eye

31. The Buccal nerve:
1 cm below zygomatic arch
2 in number -Upper deep buccal & Lower deep buccal
Runs along parotid duct
Muscles supplied :-
• Risorius (smirk)
• Buccinator (aids chewing)
Levator Labii Superioris Alaque Nasi (snarl)
• Levator Anguli Oris (soft smile)
• Nasalis (Flare Nostrils)
• Upper Orbicularis Oris
Action – Showing Teeth

32. 4. The marginal mandibular nerve:
Comes out through the ant. border of parotid
gland
Runs 1-2cm below the ramus of mandible
inferiorly
Supplies -
• Muscles of lower lip & chin
• Lower Orbicularis Oris
• Deperessor anguli oris
• Depressor labii inferioris
• Mentalis
Actions – Whistle & Puckering of Lips

33. 5. The cervical nerve:
Comes out through the lower pole of parotid gland.
Muscle Supplied – Platysma
Action – Contraction of Platysma

35. D) Communicating branches with adjacent cranial and spinal nerves
It communicates with the following neighbouring nerves at various sites:
Vestibulo-cochlear nerve, at the internal acoustic meatus
Sympathetic plexus around the middle meningeal artery, at geniculate ganglion
Auricular branch of vagus nerve, in the facial canal
9th and 10th cranial nerves, below the stylomastoid foramen
Lesser occipital nerve, behind the ear
Branches of trigeminal nerve, in the face

37. GANGLIA
The ganglia associated with the facial nerve are as follows:
1. The Geniculate ganglion:
2. The Submandibular ganglion:
3. The Pterygopalatine ganglion:

39. 1.The Geniculate ganglion:
Located on the first bend of facial nerve.
The ganglion is formed by the juncture of the nervus intermedius and the facial nerve into a
common trunk.
Taste fibres present in the nerve are peripheral processes of pseudo unipolar neurons
present in geniculate ganglion.
Nerves that branch from geniculate ganglion
• The greater petrosal n.
• External petrosal n.

40. 2. The Submandibular ganglion:
It is small and fusiform in shape.
It is situated above deep portion of submandibular gland, on the hyoglossus muscle
near posterior border of mylohyoid.
The ganglion hangs by two nerve filaments from lower border of the lingual nerve.
Parasympathetic ganglion relay of secretomotor fibres to the submandibular and
sublingual glands.
The preganglionic fibre come from Chorda tympani nerve.

41. 3. The Pterygopalatine ganglion:
Also called Sphenopalatine ganglion, Meckel’s ganglion or nasal ganglion.
Present in Pterygopalatine fossa.
The fibres reach the ganglion from the nerve to the pterygoid canal.
Secretomotor fibres meant to the lacrimal gland relay in this ganglion.
It is largely innervated by Greater petrosal nerve.

42. ARTERIAL SUPPLYAND VENOUS DRAINAGE
Supplied -
Intracranially –
anterior inferior cerebral artery
In canal –
superficial petrosal branch of middle meningeal artery &
stylomastoid branch of post. auricular or occipital arteries.

43. Extracranially – branches from -
stylomastoid,
post auricular,
occipital,
superficial temporal &
transverse facial arteries.
Venous drainage – into the venae comitantes of superficial petrosal
and stylomastoid arteries.

44. CLINICAL EXAMINATION OF FACIAL NERVE
Examination of the Motor Functions
Inspection-
• Facial asymmetry, nasolabial fold with forehead wrinkles, movements during
spontaneous facial expression.
• Tone of the muscles of facial expression,
• Atrophy and fasciculations
• Abnormal muscle contractions and involuntary movements
• Spontaneous blinking for frequency and symmetry.

45. Testing of Facial Nerve Branches
Testing the temporal branches of the facial nerve – patient is asked to frown and
wrinkle his or her forehead.
Testing the Zygomatic branches of the facial nerve- patient is asked to close their
eyes tightly
Testing the buccal branches of the facial nerve
• 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

46. 1.Examination of Reflexes
Corneal Reflex
• Afferent limb of the reflex is mediated by CN V-1, the efferent limb by CN VII.
Stapedius reflex
• Nerve to stapedius muscle test
• Impedence audiometry can record the presence or absence of stapedius muscle
contraction to sound stimuli 70 to 100 db above hearing threshold.
• Absence reflex or a reflex less than half the amplitude is due to a lesion proximal
to stapedius nerve

47. Examination of Sensory Functions
Hypesthesia of posterior wall of the external auditory meatus in proximal facial
nerve lesions.
Taste on anterior two-thirds of the tongue-
use four substances for testing:
• Sucrose (sweet), sodium chloride (salty), quinine (bitter), and citric acid (sour).
• Patient with a peripheral pattern of facial weakness has impaired taste, the lesion is
proximal to the junction with the chorda tympani.

48. Examination of Secretory Functions
• Tear production may be quantitated with the Schirmer test.
• Lacrimal reflex is tearing, usually bilateral, caused by stimulating the cornea.
• Nasolacrimal reflex is elicited by mechanical stimulation of the nasal mucosa, or
by chemical stimulation using irritating substances such as ammonia.
• Abnormalities of salivation are usually suggested by the history.

49. TOPOGNOSTIC TESTING - tear-hear-taste-face
1. Schirmer test for lacrimation (GSPN)
2. Stapedial reflex test (Stapedial branch)
3. Taste testing (Chorda tympani nerve)
4. Salivary flow rates & pH (Chorda tympani)
ELECTROPHYSIOLOGIC TESTS
1. Nerve stimulation test (NST)
2. Electromyography(EMG)
3. Maximal stimulation test (MST)

50. APPLIED ANATOMY
1. FACIAL NERVE PALSY
Paralysis of facial nerve
FACIAL NERVE
PALSY
UPPER MOTOR
NEURON TYPE
LOWER MOTOR
NEURON TYPE

51.  Upper motor neuron type
Most common in patient with cerebral hemorrhage which is always associated with hemiplegia.
Paralysis of the contralateral lower part of face below the palpebral fissure.
Upper part of the face is spared.
2) Lower motor neuron type
2 types-
• nuclear paralysis
• infranuclear paralysis
In nuclear paralysis motor nucleus of facial nerve is involved due to poliomyelitis or lesions of the
pons. Paralysis of muscles of the entire face on ipsilateral side.
Infranuclear paralysis occurs due to injury of facial nerve and clinical effects vary according to
site of injury.

52. Injury proximal to geniculate ganglion
Diminished lacrimation, hyperacusis, loss of facial expression, loss of salivation and taste
sensation
Injury in the middle ear segment of the nerve
All the above effects except that there will be no loss of lacrimation
Lesion of the nerve within mastoid foramen
All the above effects except that there will be no loss of lacrimation and no hyperacusis
Injury at or distal to stylomastoid foramen
Most common in children due to absent mastoid
Paralysis of muscles of facial expression
No loss of lacrimation
No loss of taste sensation
No hyperacusis
No loss of salivation

55. BELL’S PALSY
Most common lower motor neuron type of facial involvement.
Affects men and women equally.
Characterised by acute unilateral infranuclear paralysis.
Mostly it is idiopathic and leads to paralysis of muscles of facial expression.
Facial muscles of the same side are paralyzed and lead to the following features-
 Facial asymmetry
 Loss of wrinkles on forehead
 Widening of palpebral fissure and inability to close eye
 Accumulation of food into the vestibule of the mouth
 Dribbling of saliva from the angle of mouth
 Inability to draw the angle of mouth upward and laterally while laughing

57. ETIOLOGY:
• Idiopathic
• Herpes simplex virus-1
• Herpes zoster is probably second most common viral infection associated.
• Other viruses implicated include Cytomegalovirus, Epstein-Barr virus, Human
Herpes virus 6, and Coxsackie.
• Inactivated intra nasal influenza vaccine.

58. CLINICAL FEATURE
• Onset of bell’s palsy is acute.
• Half of the cases attain maximum paralysis in 48 hours.
• All cases are clinically prominent by 5 days.
• Pain behind the ear may precede the paralysis by a day or two.
• Impairment of taste is present to some degree in all cases – rarely beyond second week of
paralysis.
• Hyperacusis or distortion of sound in ipsilateral ear -paralysis of stapedius muscle.
• Paralysis is partial in 30%, complete in 70% cases.
• About 1% of cases are bilateral

59. PROGNOSIS
• 80% patients recover within a few weeks (2-12 weeks)
• 10% permanent long term sequelae
• 8% recurrence
TREATMENT
• Symptomatic
• Protection of eye during the sleep
• Massage of the muscles

60. • Lubricating eye drops
• Prednisolone 60-80 mg/day in divided doses for intial 4-5 days, then taper over
next 7-10 days.
• Acyclovir alone is not useful.
• Acyclovir 400 mg 5 times a day –10 days
• Valacyclovir 1000 mg /day 5-7 days.
• No evidence that surgical decompression of facial nerve is effective ---may be
harmful.

61. TRASIENT DELAYED FACIAL NERVE PALSY
Occur following inferior alveolar nerve block
Two hypothesis have been put forward to explain this-
Firstly, mechanical stimulation of the sympathetic plexus by needle or anaesthetic solution leading
to stimulation of stylomastoid sympathetic plexus. This causes a delayed reflex spasm of the vasa
nervorum of the facial nerve, leading to ischemic neuritis and secondary oedema.
Secondly, reactivation of a latent viral infection due to the injection trauma may be responsible for
neural sheath inflammation and consequent disturbance in function.

62. PREVENTION
Too medial direction during injection should be avoided.
Tip of the needle should contact the bone before depositing the solution.
The needle should not be inserted till the hub.

63. DIAGNOSTIC TESTS:
Hearing test- Bing test (a vibrating tuning fork is held to the mastoid process
and the auditory meatus is alternately occluded and left open; an increase
and decrease in loudness is perceived by the normal ear and in
sensorineural hearing loss, whereas the hearing of no difference occurs in
conductive hearing loss.) .
Imaging: CT or MRI .
Electrical Test

64. TREATMENT
♦ The use of paper tape to depress the upper eyelid during sleep and prevent corneal
drying,
♦ Massage of the weakened muscles.
♦ Glucocorticoids, (prednisone 60–80 mg daily during the first 5 days and then
tapered over the next 5 days)

65. Disorders of facial nerve-
underactivity
overactivity
GULLIAN BARRE SYNDROME (acute idiopathic Polyneuritis)
Ascending paresis with depressed tendon reflexes (acute symmetrical polyneuropathy)
Occuring 1 to 3 weeks (occassionally upto 8 weeks)
Follows non-specific respiratory or gastrointestinal illness.
Specific infections such as with Herpes group of viruses (CMV, EBvirus), campylobacteria jejuni
After immunization

66. Begins with myalgia or paraesthesias of the lower limbs, followed by weakness,
which often involve abdominal, thoracic and upper limb muscles.
Impaired swallowing or paraesthesias of the mouth and face.
Bilateral facial weakness is common.
Plasmapheresis is of value.

67. MELKERSSON ROSENTHAL SYNDROME-
Alternating recurrent facial palsy
facial oedema
Fissured tongue
T/t: Intralesional corticosteroids, Surgical reduction of granulomatous tissue.
RAMSAY HUNT SYNDROME (geniculate herpes , otitic herpes)
Association of facial paresis with herpetic eruptions (blisters) along the ipsilateral
external auditory meatus
History of recurrent viral syndrome and auricular pain
Mostly involve hard and soft palate

68. RAMSAY HUNT SYNDROME

69. CROCODILE TEAR SYNDROME -
Injury to facial nerve proximal to geniculate ganglion
So there is misdirection of nerve fibres to lacrimal gland instead of submandibular
gland through the greater petrosal nerve
Patient lacrimates while eating.
HEERFORDT’S SYNDROME -
Uveitis, parotitis and mild pyrexia
Facial nerve is the most commonly involved cranial nerve in sarcoidosis (because of
the infiltration of nerve by sarcoid granulomas)
T/t: Corticosteroids

70. MOBIUS SYNDROME
Congenital complete or partial facial nerve palsy with or without paralysis of other
cranial nerves.
Associated with other malformation
Present with mask like facies,
May be associated with squint , tongue hypoplasia, swallowing difficulties

71. Disorders of overactivity Habit spasm of the face (Nervous twitch)
Characterized by stereotypical, repetitive facial movements
T/t: Reassurance
Essential Blepharospasm
Form of cranial dystonia (limited to the orbicularis oculi muscle)
Excessive blinking
Blinking gradually intensifies in character, insidiously becoming a spasm
Disease progresses, the eye closure become so frequent and prolonged that the patient is
functionally blind.

72. TUMOURS:
Facial Neuromas:
Non-malignant fibroid growth may grow in the facial nerve itself, producing a
gradually progressive facial nerve paralysis.
Arise from any segment of the nerve from the cerebellopontine angle to the
extratemporal peripheral portion .
Slowly progressive or sudden facial weakness, often preceded by facial twitching.

73. Acoustic neuromas:
Non-malignant fibrous growths, originating from the balance or hearing nerve, that
do not metastasize.
Impair hearing, facial nerve function.
Acoustic tumors are in intimate contact with the facial nerve.
Temporary paralysis of the face and muscles which close the eyelids is common
following removal of an acoustic tumor.

74. Parotid gland tumours:
Facial nerve paralysis associated with a parotid gland tumour classically denotes
malignancy.
Facial nerve paralysis secondary to Warthin’s tumour of the parotid gland.
It is important for clinicians to be aware that, on rare occasions, facial nerve
dysfunction may result from benign parotid disease.
Parotid gland tumor are often associated with carcinomatous infiltration into facial
nerves.

75. BACTERIAL INFECTIONS:
Lyme Disease ( Lyme Borreliosis)
Caused by group of spirochetal infection, Borrelia
burgdoferi
bacteria may enter the body through the skin at the
site of tick bite and produce flu like symptoms.
C/F: red ring around the site of the tick bite. -
cranial neuropathies, headache, seizures and
vertigo.
T/t : i.v. Penicillin or oral Doxcycline

76. VIRAL
Herpes simplex virus(HSV-1)
- most frequent cause of Bell’s Palsy
- Virus often remains dormant.
- Triggers not known but causative factor: decreased immunity , stress, URI , lack
of sleep, etc.
- This leads to inflammatory reaction which put pressure on nerve, compress it
and resulting into Bell’s Palsy

77. Human immunodeficiency Virus-
• Can cause Bell’s Palsy.
• Early stage paralysis due to viral infection
• In later stage it may due to opportunistic infections.
FUNGAL INFECTIONS:
• Intracranial Aspergillosis:
• Involving the internal auditory canal and inner ear in an immunocompetent
patient
• C/F: facial weakness
• T/t : Amphotericin B

78. DIFFERENTIAL DIAGNOSIS
 Facial Palsy is bilateral and symmetrical in the case of changes in
the neuromuscular junction (like in myasthenia gravis) or in the
case of muscle disorders, and it is not caused by facial nerve
damage.
 In extrapyramidal syndromes such as Parkinson’s disease, the
patient’s facies is immobile, but voluntary movements are possible
without the facial nerve being affected.

79.  In Cayler syndrome, the unilaterally missing depressor anguli oris muscle
determines neonatal facial asymmetry (neonatal asymmetric crying facies),
which is a developmental disorder.
 Möbius syndrome, which is characterized by the partial or complete absence of
nerves VI and VII, involves genetic and environmental factors.

80. DENTAL CONSIDERATIONS
IN FACIAL NERVE
DISORDERS

81. MANAGEMENT OF PATIENT WITH FNP IN DENTAL OFFICE
In the dental office, the dentist may have to examine patients with facial asymmetry and
functional disorders caused by facial paralysis (FP).
It is important for the dental practitioner to establish whether FP was caused by injury to
the facial nerve, and to focus on the site of the lesion and potential risk factors.
The risks of dental treatment in a patient with FP should also be assessed.
The dentist may treat a patient with FP, or may be the first medical professional to
observe FP in a patient, or can even induce iatrogenic reactions themselves.

83. CHALLANGES FACED BY A DENTAL PRACTITIONER
1. DRY MOUTH
2. LACK OF GENERAL SENSATION OF TONGUE D/T CHORDA TYMPANI
3. DROOPING OF MOUTH
4. DROOLING OF SALIVA

84. 5. ANGULAR CHELITIS
6. TRISMUS
7. FOOD LODGEMENT IN POUCH
- INCREASED CARIES INCIDENCE
- DELAYED HEALING POST SURGICAL PROCEDURES
8. CHEEK BITING

85. 1.DRY MOUTH
Nerve damage may result in the reduced production of tears and saliva.
Patients with decreased salivary flow may experience xerostomia, which
increases the risk for dental caries.

86. MANAGEMENT
There are a number of products available to address the effects of xerostomia,
including those containing
• fluoride,
• calcium phosphate,
• antimicrobials,
• sodium bicarbonate, and
• xylitol.

87.  These products can increase lubrication and decrease the loss of minerals from
tooth surfaces by improving the buffering ability of saliva.
 Sugar-free gum, sugar-free hard candies and ice chips can also help relieve dry
mouth.
 Patient should keep himself adequately hydrated.
 It is always recommended for patients to avoid carbonated drinks, caffeine,
alcohol and tobacco and use of lanolin-based lip balm to help moisturize their
dry lips.

88. 2. LACK OF GENERAL SENSATION ON ANTERIOR 2/3RD
OF TONGUE
General sensation to the anterior two-thirds of the tongue is by innervation from the
lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V3).
The lingual nerve is located deep and medial to the hyoglossus muscle and
is associated with the submandibular ganglion.
A lesion of facial nerve at the level of submandibular ganglion can lead to altered
general sensation due to involvement of chorda tympani which carries the fibres of
lingual nerve alongwith.
This may lead to tongue biting while performing dental procedures since the patient
cannot feel any sensation of pain, pressure or temperature on involved side.

89. PREVENTION
1. Use of towel clips to hold the tongue.
2. Instruct the patient about the condition.

90. 3. DROOPING OF MOUTH ON IPSILATERAL SIDE
Bell's palsy is a sudden weakness or paralysis on one
side of the face that makes it hard for a person to move
the mouth, nose, or eyelid.
It also can make that side of the face droop or look stiff.
This can be problematic while performing a dental
procedure as it may hinder access intraorally.

92. Alongwith these measures,
the appointments should be kept short so as to avoid straining the facial muscles.

93. It is most commonly caused by poor oral and
facial muscle control.
Sialorrhea causes a range of physical and
psychosocial complications, including perioral
chapping, dehydration, odour, and social
stigmatization, that can be devastating for
patients.
Many interventions are used to reduce or
eliminate drooling.
4. DROOLING OF SALIVA FROM CORNER OF MOUTH

94. These include surgery, medications, botulinum toxin (BoNT-A and BoNT-B),
physical therapies, therapies to improve sensory function, behavioural therapies to
assist the patient in managing his/her own drooling, appliances placed in the mouth,
and acupuncture.
Anticholinergic medications, such as glycopyrrolate and scopolamine, are effective
in reducing drooling.
Robinul is an anti-spasmodic. It is also used to reduce secretions from the salivary
glands, pharynx (part of the throat), trachea (windpipe), and bronchi (air tubes that
lead to the lungs). Robinul also acts as an anticholinergic.

95. NOLA DRY FIELD SYSTEM

96. 5. ANGULAR CHELITIS
Angular cheilitis (AC) is inflammation of one or
both corners of the mouth. Often the corners are red
with skin breakdown and crusting.
Saliva pools in the fissures, creating a chronic
moist environment for infection with Candida
albicans, Staphylococcus
aureus and/or Streptococcus (rare)
It can also be itchy or painful and can be an
obstruction to dental treatment.

97. MANAGEMENT
• Prescribe a topical ointment or cream: Usually a combination of topical antifungal
and antibacterial (e.g., nystatin and mupirocin);
•Consider the use of combination antifungal/antibacterial/glucocorticosteroid
ointment as an alternative.
•Apply a thin layer to the angles of the mouth 2–3 x daily for 2 weeks.

98. 6. FOOD LODGEMENT IN POUCH
Bell’s palsy can cause negative oral health effects.
Due to the increased risk of caries in this population, consider the application of fluoride
varnish and/or prescribe home-based fluoride therapies.
The loss of muscle tone on the affected side may interfere with the patient’s ability to
chew food.
Food can also become trapped in the vestibule of the cheek due to the impaired buccinator
muscle that normally aids in moving food onto the occlusal plane.

99. This may lead to an increase in dental biofilm accumulation.
Emphasize the importance of twice daily brushing and flossing to patients with
Bell’s palsy.
If flossing compliance is an issue, interdental brushes and flossing aids should be
recommended.
Patients also need to rinse with water after eating to remove food particles that may
be trapped in the vestibule.

100. 8. DELAYED HEALING POST SURGICAL PROCEDURE
Due to loss of muscle tone on the affected side patient’s ability to chew food
is decreased.
Food can also become trapped in the vestibule of the cheek which is
otherwise cleared out in a healthy patient.
This may lead to an increase in dental biofilm accumulation,
This can lead to delayed healing at the site of surgery.

101. MANAGEMENT
Emphasize the importance of twice daily brushing and flossing to patients with
Bell’s palsy.
The addition of a therapeutic mouth rinse and irrigation with a dental water jet to
the self-care regimen may be indicated.
If flossing compliance is an issue, interdental brushes and flossing aids
should be recommended.
Patients also need to rinse with water after eating to remove food particles
that may be trapped in the vestibule.

102. Trismus means being unable to open the mouth completely.
Normal full jaw opening is 40 – 50 millimetres.
Trismus can be caused by damage to the muscles and/or nerve
responsible for opening and closing the mouth and for chewing.
The main treatment for trismus is jaw exercises to gently help improve
mouth opening.
There are some specific medical devices that can be particularly helpful.
7. TRISMUS

104. 9. CHEEK BITING
Individuals with facial paralysis are prone to biting the surface of their inner gums
on the affected side, which can lead to ulcerations and infection.
MANAGEMENT
Mouth guard:
Wearing a mouth guard can stop a patient from biting cheeks.
Patient education:
It is essential to raise patients’ awareness of cheek biting as an unhealthy habit and
in need of elimination.

105. NERVE INJURY
PATHOPHYSIOLOGY
Neuropraxia : Blocks flow of axoplasm from stoma to distal axon.
Axonotemesis : Wallerian degeneration with intact endoneural tubules.
Neurotemesis : Wallerian degeneration with loss of endoneural tubules .
Transection : Complete division of the nerve .

107. CAUSES OF NERVE PALSY
CONGENITAL
NEUROGENIC
TRAUMATIC
NEOPLASTIC
INFECTIOUS
IATROGENIC
OTHERS

108. CHILD ADULT
Chorda tympani may exit through
stylomastoid foramen
Chorda tympani exits proximal to
stylomastoid foramen
Nerve trunk is more anterior and
lateral on exit through stylomastoid
foramen.
Nerve trunk is less anterior and deeper.
Nerve is more superficial on angle of
mandible.
Nerve is less superficial on angle of
mandible.
2nd genu is more acute and lateral. 2nd genu is less acute and lateral.
AGE CHANGES

110. CASE 3:

112. IATROGENIC FACIAL NERVE INJURY
The administration of local anaesthesia is an integral procedure of everyday practice in
dentistry.
The attainment of adequate analgesia in the operating field is essential in order to
achieve the required cooperation with the patient and complete the session
successfully.
However, this common procedure may trigger the appearance of a variety of
complications, systemic or localized.

113. There are two types of facial palsy following inferior alveolar block anaesthesia, whose
differences in clinical appearance derive from their separate pathogenic backgrounds.
1.The immediate type is due to the direct accidental anaesthesia of one or more branches of the
facial nerve.
This is possible when an intraglandular injection of the anaesthetic solution occurs. More
specifically, if the injection is administered too far posteriorly, the anesthetic solution could be
injected into the parotid substance, whose deep lobe extends around the posterior ramus of the
mandible and projects forward on the medial surface of the ramus.

114. Most often, the gland envelopes the facial nerve, thus leading to the direct
anaesthesia of the latter.
HOW TO AVOID?
The needle should not be inserted till the hub.
Too medial direction during injection should be avoided.
Tip of the needle should contact the bone before depositing the solution.

115. 2.Pathogenesis of the delayed type palsy is more complicated.
Firstly, the palsy could result from a sympathetic vascular reflex, leading to ischemic
paralysis in the stylomastoid foramen region. The anaesthetic solution, its breakdown
products, or even the mechanical action of the needle itself, may lead to stimulation of
the sympathetic plexus associated with the external carotid artery, which in turn
communicates with the plexus covering the stylomastoid artery as it enters the parotid
gland.
HOW TO AVOID?
Avoid administering too much quantity of anaesthetic solution.

116. The trauma involved in the procedure of dental anaesthesia could act as a releasing factor,
reactivating a latent viral infection such as herpes simplex virus (HSV) or varicella-zoster virus
(VZV). The above could be responsible for neural sheath inflammation and consequent facial
nerve palsy.
HOW TO AVOID?
Standard precautions such as aspiration, slow injection, and continuous monitoring of the patient
could minimize the chance.
Thirdly, alternative pathways for the breakdown of local anaesthetic solutions may cause
aromatic alcohols to form around the nerves. According to the dental literature, this may result in
the equivalent of an alcohol block, leading to prolonged nerve damage.

117. Fourthly, prolonged instrumental opening of the mouth has been associated with facial palsy, due
to stretch of the facial nerve.
HOW TO AVOID?
Avoid longer duration of appointments.
Prefer multiple-sitting procedures
Finally, a different mechanism has been proposed in the literature involving direct intravascular
administration of the anaesthetic solution. Rood showed that the pressure created during an intra-
arterial injection is more than enough to cause backward flow of the anaesthetic agent.

118. CASE 2:

126. SODIUM HYPOCHLORITE ACCIDENT
The immediate sequel of accident include severe sudden excruciating pain and swelling
in the tissue in area involved.
MANAGEMENT
Administration of local anaesthesia for pain relief.
Canal should be Immediately irrigated with copious amount of normal saline.
Analgesic and antibiotics should be prescribed for post operative pain management and
to prevent secondary infection.

127. Non surgical management may be sufficient but surgical intervention should be
considered to manage the ill effects.
Surgical intervention may be considered in some cases depending upon the grade of
injury and response to treatment.
The goal of surgical intervention should be to achieve decompression, ease drainage
and improve prognosis.

128. Upon the appearance of facial palsy, the patient should be reassured and fully informed about any
symptoms that may occur.
For both immediate and delayed palsy, management of facial palsy should include proper
protection and lubrication of the eye.
An eye patch should be applied, especially during night time, while artificial tears can be used
during the day, along with sunglasses, to prevent exposure keratitis.
Any corneal abrasion or infection should be treated immediately to avoid possible visual function
complications.
PRIMARY MANAGEMENT

129. Treatment for delayed type of palsy can also be treated similarly for patients with idiopathic facial
nerve palsy.
The main drug therapy is steroids, they have been proven to be beneficial in improving the
outcome of the palsy, when given immediately. These drugs hasten the recovery and lessen the
ultimate degree of dysfunction.
The patient should be referred to a neurologist for further evaluation and a clinical follow-up must
be organized. The recovery is often total, but slow and progressive.

130. CASE REPORT
CASE1 :

135. CONCLUSION
Facial nerve is an important cranial nerve of the head and neck
region.
Though injury to Facial Nerve is a rare occurrence in a dental setup
but it is important to understand the course, relations, distribution
and branches of facial nerve to avoid trauma during procedures
performed in the head and neck regions.
Also following a proper protocol and management of complication
are mandatory during any mishappening.

137. References
 GRAY ANATOMY 37 TH EDITION
 CLINICAL ORIENTED ANATOMY 5 TH EDITION, page no.
 B.D CHOURASIA’S HUMAN ANATOMY 4 TH EDITION , VOL- 3
 BURKET’S ORAL MEDICINE DIAGNOSIS AND TREATMENT, 10 TH
EDITION
 NETTERS: COLOUR ATLAS OF ANATOMY