69
FACIAL NERVE
FACIAL NERVE
Anatomy Nuclei Course Branches and distribution Ganglia Blood supply
Functional ComponentsFunctions of the Facial NerveClinical Examination of the Facial NervePathology of the Facial Nerve Importance of facial nerve in operative dentistryEndodontic implications of facial nerveConclusion
CONTENTS
04/08/2023 3
NerveSympatheticParasympatheticNeuronNucleiMotor/Efferent (Brachial, visceral)Sensory/Afferent (General, special)Upper motor neuronLower Motor neuronParesis Plegia
Key terms:
04/08/2023 4
ANATOMY
• 7th Cranial
nerve
• Mixed nerve
• Nerve of the
hyoid arch
04/08/2023 5
NUCLEI
• Four nuclei -
Motor nucleus (branchiomotor)
Superior salivatory nucleus (parasympathetic)
Lacrimatory nucleus (parasympathetic)
Nucleus of tractus solitarius (gustatory)
04/08/2023 6
Nerve innervation by the Motor Nucleus in the upper and lower part of the face
04/08/2023 7
Origin
04/08/2023 8
Relationship of the cranial nerves in the internal acoustic meatus
VIII
VII (m)
Labrynthine vessels
Dura
Arachnoid
Nervus intermedius
04/08/2023 9
04/08/2023 10
INTRACRANIAL COURSE
04/08/2023 11
DISTRIBUTION OF FACIAL NERVE WITHIN THE TEMPORAL BONE
04/08/2023 12
Stylomastoid Foramen
04/08/2023 13
EXTRACRANIAL COURSE
Within the facial canal
At its exit from the stylomastoid foramen
Terminal branches within the parotid gland
Communicating branches with adjacent cranial and spinal nerves
Branches and Distribution
1404/08/2023
04/08/2023 15
BRANCHES AND DISTRIBUTIONWithin the facial canal
1. Greater Petrosal Nerve
2. Nerve to the stapedius muscle
04/08/2023 16
04/08/2023 17
3. Chorda Tympani Nerve
04/08/2023 18
COURSE OF CHORDA TYMPANI NERVE
04/08/2023 19
Tongue
Sublingual
gland
Submandibular Gland
Submandibular Ganglion
Lingual nerve
carrying general
sensation
Chorda tympani
taste fibre
Chorda tympani Secretomotor
fibre (preganglionic)
04/08/2023 20
At its exit from the stylomastoid foramen1. Posterior auricular 2. Digastric 3. Stylohyoid
04/08/2023 21
Terminal branches within the parotid gland
CervicalMandibular
Buccal
Zygomatic
Temporal
04/08/2023 22
Anatomic Variations
04/08/2023 23
In the internal acoustic meatus - With the acoustic nerve at the
geniculate ganglion
With the sphenopalatine ganglion by the greater superficial petrosal nerve.
With the otic ganglion by a branch which joins the lesser superficial petrosal nerve.
In the facial canal - With the auricular branch of the vagus.
At its exit from the stylomastoid foramen - With the glossopharyngeal.
On the face - With the trigeminal.
In the neck - With the cutaneous cervical.
Branches of Communication
04/08/2023 24
Ganglia Of The Facial Nerve
04/08/2023 25
The facial nerve derives both an intrinsic and an extrinsic blood supply.
Intrinsic – middle cerebral artery
Extrinsic - the stylomastoid
artery the middle
meningeal artery the anterior
cerebellar artery
Blood supply of the Facial Nerve
04/08/2023 26
Functional Components1. Branchial
Motor
2. Visceral Motor
3. Special Sensory
4. General Sensory
04/08/2023 27
Clinical Examination of the Facial NerveMotor Examination
04/08/2023 28
Testing Taste
04/08/2023 29
Corneal Reflex
04/08/2023 30
Sucking Reflex
04/08/2023 31
EFFERENT FUNCTION
04/08/2023 32
04/08/2023 33
AFFERENT FUNCTION
04/08/2023 34Review Article The receptors and cells for mammalian taste Nature 444, 288-294 (16 November 2006)
04/08/2023 35
Physiology of Nerve injury
Sunderland's classification – five degrees Neuropraxia – 1st degree Axonotmesis – 2nd degree Endoneurotmesis – 3rd degree Perineurotmesis – 4th degree Neurotmesis – 5th degree
Pathology
04/08/2023 36
Facial paralysis is a dysfunction of the facial nerve that results in inability to control facial muscles on the affected side.
Facial Palsy
04/08/2023 37
Congenital/Acquired
Brain or parotid gland tumours
Trauma
Stroke
Lyme disease
Latent virus reactivation of zoster and Epstein Barr
Idiopathic – Bell’s Palsy
Causes
04/08/2023 38
I - Normal facial movements; No synkinesis
II - Slight Mild deformity, mild synkinesis, good forehead function, slight asymmetry
III - Moderate Obvious facial weakness, forehead motion present, good eye closure, asymmetry, Bell's phenomenon present
IV - Moderately Obvious weakness, increasing synkinesis; no forehead motion
V - Severe Very obvious facial paralysis, some tone present, cannot close eye
VI - Total Complete facial paralysis, absent tone
Grade Of Facial Paralysis House - Brackmann score
04/08/2023 39
Paralysis involving all divisions of the facial nerve is peripheral and that sparing the forehead is central.
Central versus Peripheral Paralysis
04/08/2023 40
Central Seven
It usually results from damage to upper motor neurons of the facial nerve.
Most commonly occurs due to stroke.
Central Facial Palsy
04/08/2023 41
Named after Scottish anatomist Charles Bell
Idiopathic, unilateral, self-limiting facial palsy
Infranuclear/lower motor type
Persistent latent viral infection activation, exposure to cold
Facial drooping on the affected side
Bell’s Palsy
04/08/2023 42
As a result of inflammation of the facial nerve, pressure is produced on the nerve where it exits the skull within its bony canal, blocking the transmission of neural signals or damaging the nerve.
Pathology
SymptomsClassic presentation – weakness on one side
of faceAwareness – drooling after brushing teeth or
drinking, asymmetry
04/08/2023 43
Signs
04/08/2023 44
BELL’S PHENOMENON
INFRANUCLEAR (LMN):a. Lesion at or below stylomastoid foramen – loss of facial expression on the same side as the lesionb. Lesion in the facial canal (lower level)– a + loss of taste sensation in anterior 2/3 rds of tongue and salivationc. Lesion in the facial canal (higher level) – a + b + loss of hearingd. Lesion at genu/proximal to genuculate ganglion – a + b + c + loss of lacrimation
Level of the lesion and the corresponding symptoms
04/08/2023 46
NUCLEAR LESION (LMN):Lesion in pons – unilateral facial palsy (6th nerve involvement also seen)
+ Contralateral pyramidal
signs (Millard Gubler syndrome)
04/08/2023 47
SUPRANUCLEAR LESION (UMN) :Contralateral lower side of face involved (voluntary movement) facial expressions
+Unilateral pyramidal signs (UMN type)
(Hemiplegia)
04/08/2023 48
Bell's palsy is a diagnosis of exclusion.
Lyme disease
Tumours (e.g., Acoustic neuroma , parotid gland tumours)
Ramsay Hunt syndrome
Demyelinating lesions
Sarcoidosis
Differential Diagnosis
04/08/2023 49
Heerfordt's syndrome
Melkersson-Rosenthal syndrome
Gustatory tearing or crocodile tears
Syndromes associated with Bell’s Palsy
04/08/2023 50
Guillain-Barré syndrome
04/08/2023 52
Ramsay Hunt Syndrome
Eye care
Oral steroid – Prednisone 1 mg/kg/day for 10-14 days
Surgery to relieve pressure on the nerve
Local superficial heat therapy (i.e. hot pack or infrared rays) for 15min/session (Europa Medicophys 2006;42:41-7)
Physiotherapy (Physiotherapy treatment of Bell's palsy: a case report New Zealand Journal of
Physiotherapy, Nov, 2006 by James M. Elliott )
Facial muscle protection
Treatment
04/08/2023 54
Described by Gowers in 1884
A neurological disorder wherein blood vessels constrict the facial nerve causing facial spasm.
First symptom - intermittent twitching of the eyelid muscle leading to forced closure of the eye.
Hemifacial Spasm
04/08/2023 55
YouTube- HemiFacialSpasm before amp after.flv
04/08/2023 56
Treatment Medications -
carbamazepine, phenytoin and gabapentin
Injection of botulinum toxin type A
04/08/2023 57
Microvascular Decompression
04/08/2023 58
Trauma – Petrous bone fracture Surgery of middle ear,
mastoidectomy, parotid glandTumours – Neuroma/schwanoma
Meningioma Hemangioma Metastasis Osteopetrosis
FACIAL NERVE TRAUMA AND TUMOURS
04/08/2023 59
The transient loss of motor function of the orofacial muscles can hamper the smile line evaluation, an important parameter for restorative and prosthetic dentistry approaches.Chiche G, Pinault A. Esthetics of anterior fixed prosthodontics. Chicago: Quintessence, 1994.
IMPORTANCE OF FACIAL NERVE IN OPERATIVE DENTISTRY
04/08/2023 60
Released and ionized mercury can be taken up by tissues and nerves beneath fillings and in root canals.
Current animal experiments show that mercury is taken up by nerve endings and is transported towards the central nervous system in the same way as lead (Baruah, 1981).
When the amalgam fillings in the right part of the lower jaw were removed, the painful strain after the facial paralysis, present four years, disappeared. It seems close at hand to suspect a combination of the general poisoning and the mercury source in the two teeth in the lower jaw as primary causes of the nerve inflammation, resulting in the face paralysis on the same side.
Mercury Poisoning From Dental Amalgam Jaro Pleva, Ph.D.1
Orthomolecular Psychiatry, volume 12, Number 3, 1983 Pp. 184-193
04/08/2023 61
Neurological complications following extrusion of sodium hypochlorite solution into the facial soft tissues during root canal treatment International Endodontic Journal, 38, 843–848, 2005
Neurological sequelae can follow inadvertent hypochlorite extrusion.
Early recognition may avert a potentially more serious outcome.
Active hospital treatment including intravenous steroids and antibiotics is recommended.
Permanent mimic musculature and nerve damage caused by sodium hypochlorite: a case report. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008 Sep;106(3):e80-3. Epub 2008 Jul 7
ENDODONTIC IMPLICATIONS OF FACIAL NERVE
04/08/2023 62
CASE REPORT - 1
04/08/2023 63
CASE REPORT - 2
04/08/2023 64
Transient facial nerve paralysis – introduction of LA into the
capsule of the parotid gland during IANB or Vazirani – Akinosi nerve block
Problem
Prevention
Management
Facial nerve palsy following intra-oral surgery performed with local anaesthesia
J.R.Coll.Surg.Edinb., 45,October 2000, 330-333
04/08/2023 65
7th cranial nerveBranches
Within facial At the stylomastoid On the faceCommunicating
canal foramen Branches
1. Greater 1. Posterior 1. Temporal
petrosal auricular 2. Zygomatic
2. Nerve to 2. Digastric 3. Buccal
Stapedius 3. Stylohyoid 4. Mandibular
3. Chorda 5. Cervical
tympani
Summary
04/08/2023 66
04/08/2023 67
“The most important thing you wear is the expression on your face.”
Certain cases of facial nerve palsy following dental or maxillofacial procedures occur.
Prevention is better than cure.
CONCLUSION
04/08/2023 68
B.D. Chaurasia’s Human Anatomy vol 3
The Facial Nerve, Mark May Barry M. Schaitkin - 2000
Handbook of Local Anesthesia 5th edition
The facial nerve: anatomy and common pathology Semin Ultrasound CT MR. 2002 Jun;23(3):202-17
International Endodontic Journal, 38, 843–848, 2005
Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008
Sep;106(3):e80-3. Epub 2008 Jul 7
Chiche G, Pinault A. Esthetics of anterior fixed prosthodontics. Chicago: Quintessence, 1994.
Mercury Poisoning From Dental Amalgam Jaro Pleva, Ph.D.1
Orthomolecular Psychiatry, volume 12, Number 3, 1983 Pp. 184-193
Color Atlas of neuroscience: Neuroanatomy and Neurophysiology by Ben Greenstein, Adam Greenstein
Neurological Classics
By Robert H. Wilkins, Robert Wilkins, Irwin Brody
REFERENCES
04/08/2023 69
Thank you
