Disorders of facial nerve with special focus for MBBS undergraduate students

1. Disorders of the facial
nerve
Dr. Krishna Koirala
2018--09-04

2. Surgical Anatomy
• Mixed nerve having 10,000 neurons (7, 000
motor and 3,000 sensory)
• Three nuclei
–Motor nucleus : Caudal Pons
–Superior salivatory nucleus : Dorsal to motor
nucleus
–Nucleus of solitary tract : Medulla

4. • Superior aspect of motor nucleus has both crossed
and uncrossed input
– Upper motor neuron lesions - only the lower part of
the face on the contralateral side will be affected
due to bilateral control to the upper facial muscles
(frontalis and orbicularis oculi)
• Inferior aspect – Contralateral input
– Lower motor neuron lesions - both upper and lower
facial weakness occurs on the same side of lesion

7. Features Upper Motor
Neuron Palsy
Lower Motor Neuron
Palsy
Forehead wrinkling B/L present Absent on same side
Eye closure B/L present Absent on same side
Naso-labial fold Absent on
opposite side
Absent on same side
Drooping of angle of
mouth
Opposite side Same side
Differences between UMN and LMN facial palsy

8. Facial Nerve Trunk (5 fiber types)
• Special visceral efferent : Muscles of facial expression,
stapedius, stylohyoid, posterior belly of digastric
• General visceral efferent : Lacrimal, nasal mucosa,
sublingual and Submandibular glands
• Special sensory : Taste from anterior 2/3 of tongue
• Somatic Sensory : EAC and concha
• Visceral afferent : Mucosa of nose, pharynx , palate

9. Course / parts of facial nerve

11. F. N .Segment Location Length
(mm)
Supranuclear Cerebral cortex NA
Brain stem Motor nucleus , superior
salivatory nucleus
NA
Meatal segment Brain stem to IAC 13-15
Labyrinthine
segment
Fundus of IAC to geniculate
ganglion
3-4
Tympanic segment Geniculate ganglion to pyramidal
eminence
8-11
Mastoid segment Pyramidal eminence to
Stylomastoid foramen
10-14
Extratemporal
segment
Stylomastoid foramen to pes
anserinus
15-20

12. • Intracranial : Pons to porous of IAC (24 mm)
• Intratemporal
– Meatal
– Labyrinthine
•Shortest (4mm), narrowest (0.68 mm)
•From fallopian canal to geniculate ganglion (1st genu)
•Branch – greater superficial petrosal nerve
•Lacks anastomosing arterial cascades : Involved in nerve
edema in fracture temporal bone and vascular
compression ,embolic phenomena, low-flow states

13. • Tympanic (Horizontal) - (13 mm)
– Geniculate ganglion to Pyramidal process (2nd genu)
– Commonly dehiscent (Damaged during surgery)
• Mastoid (Vertical) - 20mm
– Pyramid to stylomastoid foramen
– Second genu lies lateral and posterior to the pyramidal
process
– Branches : Nerve to Stapedius ,Chorda tympani ,Posterior
auricular Muscular

14. • Extracranial /
Extratemporal
– Peripheral branches
•Temporal
•Zygomatic
•Buccal
•Marginal mandibular
•Cervical

15. • Processus cochleariformis : (small bony protuberance
from which tensor tympani muscle turns 900 to insert
into malleus) lies 1 mm inferior to geniculate
ganglion
• Cog: bony ridge hanging from tegmen tympani lies 1
mm above & posterior to processus cochleariformis
• Short process of incus: 2 mm below it lies the
external genu
Surgical Landmarks of facial nerve

16. • Lateral Semicircular Canal: 2 mm anteroinfero-
medially lies the external genu
• Oval window: 1 mm above lies the external genu
• Inferior edge of Posterior S.C.C. : 2 mm anterior &
lateral lies mastoid segment of facial nerve
• Tympano-mastoid suture in posterior canal wall: 5-8
mm medial lies mastoid segment of facial nerve
• Digastric ridge in mastoid tip: leads antero-medially to
mastoid segment of facial nerve

19. Classification of Nerve injury
• Seddon (1943) : Neuropraxia, Axonotmesis ,
Neurotmesis
• Sunderland (1951)
– 10 -Neuropraxia - Complete recovery
– 20 - Axonotmesis - Usually complete
– 30 - Neurotmesis -Incomplete
– 40 - Partial transection
– 50 - Complete transection

22. Causes of Otogenic Facial Nerve paralysis
• Traumatic
– Fracture temporal bone
– Penetrating injury to middle ear/ mastoid
– Facial injuries
– Iatrogenic
• Infective
– Herpes Zoster Oticus (Ramsay Hunt syndrome)
– Acute suppurative otitis media
– Chronic suppurative otitis media Atticoantral type
– Malignant otitis externa

23. • Neoplastic
– Glomus tumors / Schwannoma
– Middle ear malignancies
– Metastatic carcinoma
• Idiopathic
– Bell’s Palsy

24. Diagnostic Tests
• Topodiagnostic Tests
– Hearing and balance
– Schirmer’s test
– Stapedial Reflex
– SM salivary flow rate
– Taste
• Electrodiagnostic Tests
– Maximal nerve stimulation
– Electromyography
– Evoked EMG
• Radiological
– CT Scan
– MRI
• Immunological
– ANA
– RA Factor
– VDRL / Monospot
• ESR
• Bone marrow ( Leukemia,
lymphoma)

25. Topodiagnostic tests
• To determine the anatomical level of a peripheral
lesion
• Principle : Lesions distal to the site of a particular
branch of the facial nerve will spare the function of
that branch
– Hearing and balance : Defects at the IAC
– Schirmer's test
• Quantitative evaluation of tear production
• Lesion at or proximal to geniculate ganglion

26. – Significant when unilateral wetness is reduced by
more than 30% of the total amount of both eyes
after 5 minutes or when bilateral tearing is
reduced to less than 25 mm after a 5-minute
period
• Stapedius reflex test
• Absence of the reflex - lesion proximal to
stapedius nerve
• Submandibular flow test
• Taste test

27. Electrodiagnostic Tests
• Nerve Excitability Test
– Technique : using a stimulating electrode over the
terminal ramifications of the facial nerve, increase
the current (milliamperes) until movement in the
appropriate muscle group is just visible
– Normal values (unaffected side of face) compared
to the side of paralysis
– Interpretation: A difference of 3.5 mamp or more -
unfavorable prognosis

28. • Electromyography ( EMG)
– Prognostic value in traumatic facial nerve injury
– Principle : A denervated muscle produces
spontaneous electrical potentials (fibrillations)
after 14 -21 days
– Presence of voluntary motor unit action potential
(VMAP) – sign of incomplete paralysis
– Early presence of VAMP ( 10-14 days) : Better
clinical outcome suggesting no need for surgical
decompression

29. • Electroneurography (Evoked Electromyography)
– Interpretation: The difference in amplitude of the
potentials of the intact and involved side of the face
correlate with the percentage of degenerated motor
fibers (denervation)
– Advantage: Quantitative analysis of amount of
degeneration
– Disadvantage: Amplitudes are a 24-48 hour
delayed representation of actual events occurring
at site of lesion

30. Clinical applications
• Facial nerve subjected to traumatic injuries of a
magnitude requiring surgical repair undergo 90%
degeneration within six days of injury
• In cases of Bell's Palsy, a poor prognosis can be
anticipated in patients reaching 95% or more
degeneration within 14 days of onset of the palsy

31. Common disorders

32. Bell’s Palsy
• Most common cause of LMN facial palsy (80%)
• Acute, idiopathic, unilateral, peripheral LMN facial
paralysis
– ? Viral prodrome ( Herpes simplex) , ? Vascular
• No sex predilection ,no side predilection
• 5th - 6th decade-Common
• 10% family history
• Pathophysiology
– Nerve swelling within the facial canal

33. Clinical Features
• Unilateral LMN Facial Paralysis : Progresses to maximal deficit
over 3 to 72 hours
• Pain (50%) : Near the mastoid process
• Excess tearing (33%) ,hyperacusis, dysgeusia
• Facial weakness
– All branches of nerve : Upper & Lower , Unilateral
– Degree : Partial (30%) ; Complete (70%)
– Affected side - flat and expressionless ,twisted intact side,
palpebral fissure wide, eye does not close

34. • Stapedius dysfunction (33%) : Hyperacusis
• Lacrimation : Mildly affected in some patients
• Taste -- No clinically significant changes in most
patients
• Sensory loss
– Mild or None
– May be present on face or tongue on side of
paralysis

36. • Natural History
– Complete / Incomplete
– Recovery begins within three weeks
– Full recovery by 6 months in 84% ( 60% in HZO )
– Recurrence : 12% ( Rare IN HZO)
– Decrease in Response to electrical testing
- Peaks in 5-10 days (10-14 days In HZO)

37. • Herpes Zoster Oticus (Ramsay Hunt
syndrome)
• Acute LMN facial paralysis caused due to Herpes
zoster virus infection of the geniculate ganglion of
the facial nerve
• Viral prodrome
• Severe pain in and around the ear
• Vesicles in pinna, face , neck ,oral cavity (100%)
• SNHL and /or vertigo (40%)

39. Treatment
1)For all cases of facial paralysis
– Reassurance
– Physical Therapy : Heat, massage
– Psychosomatic Therapy
– Physiotherapy of the face
– Eye care

40. • Eye care
– Corneal protection
•Antibiotic eye drops e.g.. Ciprofloxacin 2 drops in the
eye TDS
•Antibiotic ointment at night
•Natural tears, isotonic saline and methylcellulose drops
•Strips of skin tape to help close the eye
•Temporary patching
•Tarsorraphy
– Comfort

41. 2)For Bell’s Palsy
• Steroid Therapy
– Prednisone 1mg/kg/day ( 60-80 mg) to begin 24
to 48 h after onset and given for 1 wk, then
decreased gradually over the 2nd wk
•Helps to reduce residual paralysis
•Improves recovery
• Antiviral agents
– Acyclovir, famciclovir

42. 3)For HZO (Ramsay- Hunt)
• Antiviral agents
– Acyclovir 800mg 5 times a day for 7 days
– Best results - treatment started within three days
after symptoms appear
• Steroids
• Carbamazepine : 200-600 mg TDS
• Vaccines
– Varicella vaccine
– Zostavax (helpful in preventing viral reactivation)

43. 4) Other modalities
• Cosmetic restoration( Static Procedures)
–Fascial slings : Fascia Lata
–Tarsorraphy
–Gold weight prosthesis
–Temporalis muscle transposition
–Eyelid springs/ implants

44. Fascial Slings

45. Surgical treatment of facial nerve palsy
• Facial Nerve Decompression ( till meatal foramen)
• Nerve Repair ( Neurorraphy)
– End to end anastomosis
– Cable grafting( Sural, greater auricular)
• Nerve Transposition
– Facial - Hypoglossal anastomosis
• Muscle Transposition : Temporalis, masseter
• Micro- neurovascular muscle flaps

47. Treatment Protocol
• Up to 3 weeks : Nerve decompression or repair
• 3 weeks – 2 years
– Nerve repair or nerve transposition
• > 2 year with fibrillation in Electromyography
– Nerve repair / nerve transposition
• > 2 yr with electrical silence in Electromyography
– Muscle transposition / Eyelid implant / Fascial
sling