3. INTRODUCTION
Facial nerve is a nerve of 2nd brachial arch.
mixed nerve having 10000 fibers .
70% (7000) are myelinated motor axons to
facial muscles.
30% (3000) are sensory and
parasympathetic.
Gabriel Fallopius described the
fallopian canal for the intra
temporal portion of the Facial
nerve which is 33mm long.
4. COURSE OF THE FACIAL NERVE
INTRACRANIAL
INTRATEMPORAL
EXTRACRANIAL
5. INTRACRANIAL
CORTEX
Facial motor nerves are
represented on the cortex with
the forehead being uppermost
followed by eyelids midface lips.
7. Facial nerve hooks around nucleus of
abducens.(internal genu).
Joined by nerve of Wriesberg and
emerge from the lower border of the
Pons between olive and inf cerebellar
peduncle.
At the CP angle it is related to two
divisions of auditory nerve nervus
intermedius and post AICA.
Segment from the pons to IAM is 15-
17mm
8. The FN exits the pontomedullary
junction caudal to the trigeminal
nerve and superior to
vestibulocochlear nerve.
10. MEATAL SEGMENT
8-10 mm in length.
Enters the temporal bone via porus
acousticus lies in IAC
Association – coclear nv,
-int.auditory vessels,
- NI
11. LABRYNTHINE SEGMENT
From the fundus of the IAC continues
into the bony fallopian canal running
above the vestibule.
Reaches the medial wall of
epitympanic recess where it bends
sharply
Reddish gangliform swelling first
genu
Narrowest portion of the canal
(0.68mm) with archanoid band –
Bottle neck.
13. TYMPANIC SEGMENT/HORIZONTAL
From the genu nerve runs post and
inferiorly in the medial wall of
tympanum.
Inf to horizontal semicircular canal
superior to oval window and
promontory.
Processus cochlearformis-landmark
14. MASTOID SEGMENT/VERTICLE
From the pyramidal eminence to the
stylomastoid foramen.
Passes through the bony floor of the
aditus bends gradually forming the
second genu.
Length- 13 mm
15. Branches:
-nerve to stapedius.
Chorda tympani secretomotor
fibers to the submaxillary and
sublingual gland and taste sensation
from anterior 2/3rd of tongue.
Auricular branch
of Vagus
16.
17. EXTRACRANIAL COURSE
As its exit from stylomastoid foramen
1) Posterior auricular
Auricularis posterior, occipitalis, intrinsic muscles on
the back of auricle
2) Digastric branch
post belly of digastric
3) Stylohyoid branch-
Stylohyoid muscle
18. PAROTID PLEXUS
Course of the facial N through the
stylomastoid foramen to the
substance of the parotid gland.
Crosses the styloid proccess
Retromandibular vein
External carotid artery
To form pes anserinus
19. BRANCHES OF THE PAROTID
PLEXUS
TEMPORAL AURICULARIS ANT AND SUP.
INTRINSIC MUSCLE ON THE
LATERAL SIDE OF EAR.
OCCIPITOFRONTALIS.
ORBICULARIS OCULI
CORRUGATOR SUPERCILLI
ZYGOMATIC ORBICULARIS OCCULI
BUCCAL PROCERUS
ZYGOMATICUS MAJOR
LEVATOR LABI SUPERIORIS
LEVATOR ANGULI ORIS
ZYGOMATICUS MINOR
ALAEQUE NASI
25. EXTRAPYRAMIDAL SYSTEM
Consists of Basal Ganglia and
descending motor projections other
than CST.
Impulses are mediated through
cingulate orbital and other frontal
cortical areas and basolateral
portion of amygdala.
26. Responsible for spontaneous
emotional facial expressions.
Interplay between pyramidal and
extrapyramidal system Tonus
stabilizes motor response .
E.g destruction: Parkinsonism.
27.
28. Surgical landmarks
Mastoid & middle ear surgery
1.) Processus cochlearformis(PC)
- GG lies just ant.to PC .
- tympanic segment start at this level
- useful landmark
2.) Oval window & horizontal canal(HC)
- FN runs above the oval window & below the HC
- Tympanic wall FC at this part is thin
- Fractured easily & dehiscence is frequent
29.
30. Tympanomastoid suture line
- Lies ant. to nv & close to to the course
of CTN
- CTN & FN runs deep to this suture line.
6.) Digastric ridge
- Nv. leaves temporal bone through
SMF just ant. & lat. to sigmoid sinus
where digastric ridge turns.
31. Parotid surgery
Tragal pointer
- Sharp triangular piece of cartilage of
pinna
- nv lies 1cm deep & slightly inf. to
pointer
Post.belly of digastric muscle
- Nv. lies b/w digastric groove & styloid
process
Styloid process -Nv. crosses the lat. to
it
32.
33. Evaluation of facial nerve
Blink test
Testing of facial movement
Wrinkling the forehead & elevate of
eyebrow (temporal)
Wrinkling of nose (buccal)
Showing of teeth & blowing of cheek
(mandibular)
Grimacing (cervical)
34. Topographic testing
Schimer ‘s test
Paper strip over lower conjuctival fornix 5 min.
Result – decrease in lacrimation of 75% or more
on affected side
- b/l decrease in lacrimation (<10 mm
on both side at 5 min.
Stapideal reflex
Absent – lesion is b/w GG & stapedisus muscle
Present – lesion is distil to stapedius muscle
35. Testing for taste
Electrogaustetry method
Electric current is applied lat.border of ant
2/3 part of tongue
Metallic taste to patient
Normal – 1mA raised up to 4mA if CTN is
involved
Can be used for GSPN
Submandibular gland flow
Compare the two side
Polythene tubes passed in Wharton’s duct
Salivation – 6% citric acid
37. Electroneurography(ENoG)
Amount of severe nerve fibre degeneration
Useful b/w 4 -21 days (complete paralysis)
Bell’s palsay,trauma, acute otitis media
Objective recording of evoke compound muscle
action potential (CAMP = 5,320µv)
Supramaximal stimulus for maximal amplitude
CAMP
Degeneration >90% nerve fibre – first 14 days
- bad
Prognosis depends on rate of degeneration
Not useful in long standing > 3weeks & tumors
38. Electromyography (EMG)
Record spontaneous activity of facial muscles
At rest- muscle shows no electric activity
Voluntry contraction – normal volitional motor
unit potential
Denervated muscle- spontaneous electric
potential (fibrillation), appears after 10-21 days
Adv : incomplete/complete paralysis
: earliest sings of recovery/reinnervation
39. Supranuclear infranuclear
supranuclear infranuclear
Facial palsy of lower half
contralateral side
Ipsilateral Complete facial palsy.
Hemiplegia or hemiparesis ond/or
ataxia
No hemiplegia/ataxia
No muscle atrophy or
fasciculations
Muscle atrophy and fasciculations
Tone maintained flaccid
41. LAYERS OF THE FN.
AXON
MYLEIN SHEATH
CONNECTIVE TISSUES----ENDONEURIUM---TUBULE
MULTIPLE TUBULES COVERED BY PERINEURIUM----FASCICLE.
MULTIPLE FASCICLES COVERED BY EPINEURIUM.
42. PATHOLOGY OF NERVE INJURY
Fate of a nerve depends upon its
degree of injury.
NEUROPRAXIA: physiological
nerve conduction block with no
anatomical defect.
AXONOTMESIS: Axon sheath is
intact but axon is divided .Distal
degeneration of nerve fibers occurs.
NEUROTMESIS: Whole nerve is
severed.
43.
44. CLASSIFICATION BASED ON NERVE
REGENERATION
Sunderlands (1951) classification of
nerve injury.
House Brackmann`s classification of
grades of facial nerve paralysis
45. DEGREE
OF
NERVE
INJURY
ETIOLOGy PATHOLOGY NEUROBIO
LOGY OF
RECOVERY
TIME
PERIOD
HOUSE
BRACKMAN
N GRADE
I bells palsy,
herpes
zooster
cephalicus.
NEUROPRAXIA NO
MORPHOLO
GICAL
CHANGES
1-4WEEKS GRADE I
COMPLETE
WITHOUT
EVIDENCE OF
FAULTY
REGENERATI
ON.
2 viral and
inflammato
ry disorder.
SOM CSOM
with
Cholesteat
oma.
AXONOTMESI
S
AXONS
GROW INTO
THE INTACT
MYLINE
TUBES
1-
2MONTHS
GRADE11
FAIR
SOME
NOTICEABLE
DIFFERENCE
WITH
SPONTANEOU
S
MOVEMENTS.
MINIMAL
EVIDENCE
46. DEGRE
E OF
NERVE
INJURY
ETIOLOGy PATHOLOGY NEUROBIO
LOGY OF
RECOVERY
TIME
PERIOD
HOUSE
BRACKMAN
N GRADE
3 CSOM with
cholesteato
ma,slow
growing
neoplasms.
NEUROTMESI
S
LOSS OF
ENDONEURI
UMAXONS
GROW INTO
OTHER
TUBULES.
SYNKINESIS
2-
4MONTHS
GRADE III
MODERATE
OBVIOUS
WEAKNESS
COMPLETE
EYE
CLOSURE
GRADE IV
OBVIOUS
DISFIGURIN
G WEAKNESS
WITH
INCOMPLETE
EYE
CLOSURE
4 surgical
transection,
trauma,rapi
dly growing
neoplasm.
PARTIAL
TRANSECTION
NEW AXONS
ARE
BLOCKED
BY
SCARRING
IMPAIRS
4-
18MONTHS
GRADE V
MOTION IS
BARELY
PERCEPTIBLE
47. DEGREE
OF
NERVE
INJURY
ETIOLOGy PATHOLOGY NEUROBIO
LOGY OF
RECOVERY
TIME
PERIOD
HOUSE
BRACKMAN
N GRADE
5 complete
transection
iartrogenic
trauma.
COMPLETE
TRANSECTION
EPINEURIU
M IS
DESTROYED
.
SCAR
FILLED
GAPS
WHICH
FORM
BARRIERS
NEVER GRADE VI
NONE
49. IN CASE OF PRESSURE OR
SECTIONING: Axon of peripheral
segment of nerve are unable to
replenished by fresh axoplasm .
Live for 2-3 days with continued
electrical excitablility but without
conduction of impulses across the
site of injury.
50. COMPLICATION OF NERVE
REGENERATION
Hypokinesis: few fibers
reinnervate the muscle.
Hyperkinesis : spasm of facial
muscles due to ephahtic
transmition.
Depolarisation at the site of injury
causes firing of adjascent neuron.
51. SYNKINESIS
Abnormal synchronisation of
movement accuring with voluntary
and reflex activity of muscles that
normally do not contract together.
Range from a tiny twich of the chin
along with blinking to inability to
move any muscle seperately.
53. CONGENITAL
BIRTH TRAUMA
-forceps delivery.
-prolonged labour.
-Evidence of echymosis , lacerations.
-I II III degree of injury.
-Synkinesis may be evident in years to
come.
-in EMG there will be progressive decline
in amplitude of action potential.
54. INHERITED:
- Myotonic dystrophy:
- -autosomal dominant
- -progressive muscle wasting and
mental impairment.
- -facial is among the first to be
affected.
55. Albers schoenberg disease:
Autosomal recessive
pattern/mutation.
Disorder of bone metabolism.
Bone density increases and primary
bone resorbtion decreases.
Osteoporosis of bony canals.
Blindness deafness and facial
paralysis(III VIII VII nerve)
56. DEVELOPEMENTAL
ABNORMALITIES
Moebius syndrome:
Multiple cranial nerve
involvement(III IV V VIII X XII)
Thaliomides
Unilateral/bilateral facial palsy lower
half less affected.
59. Otitis media/otitis externa:
Acute suppuration compression of
the facial nerve at the congenital
dehiscence or along neural and
vascular structure.
Cholesteatoma granulations can
press upon the nerve.
Treatment is primarily eradication of
infection.
60. LYME DISEASE:
Tick borne spirochaete.
Facial nerve
palsy(unilateral/bilateral) is due to
bite on head or neck causes rash
headache fever.
Confirmed ELISA, antibodies to
immunoglobulin G and M.
Rx tetracyclines 3-4 weeks
Intimate relation wit middle ear cleft and ossicular chain
Together with cochlear nerve nervus intermedius int auditory artery and vein.they are ensheathed wit subarachnoid memb.
Lateral extremity
In some cases the roof maybe absent genu related to the dura matter.
Labrynthine portion of facial nerve.