Anatomy of facial nerve Components of facial nerve Branches of facial nerve Blood supply of facial nerve Surgical landmarks Electrodiagnostic tests

1. FACIAL NERVE
By N. Sindhuja
||| MBBS ; VBMC

2. INTRODUCTION
➢ Runs from Pons to Parotid
➢ Mixed nerve
➢ Both sensory root and motor root
➢ Sensory root => NERVE OF WRISBERG

3. COMPONENTS OF FACIAL NERVE :-
➢ SPECIAL VISCERAL EFFERENT : motor root
Supplies all muscles - 2nd branchial arch
➔ Muscles of facial expression
➔ Auricular muscles
➔ Stylohyoid
➔ Posterior belly of digastric
➔ Stapedius

4. ➢ GENERAL VISCERAL EFFERENT : Secretomotor
fibres to -
➔ Lacrimal glands
➔ Submandibular glands
➔ Sublingual glands

5. ➢ SPECIAL VISCERAL AFFERENT :
➔ Carries taste sensation
➔ Anterior ⅔ rd of tongue - CHORDA TYMPANI NERVE
➔ Soft & Hard palate - GREATER SUPERFICIAL
PETROSAL NERVE
➔ Carried to nucleus of tractus solitarius

6. ➢ GENERAL SOMATIC AFFERENT :
➔ General sensation from concha
➔ Posterior part of external canal
➔ Tympanic membrane
➔ Proprioception from FACIAL muscles
➔ Clinical significance : These fibres are responsible for
VESICULAR ERUPTION in HERPES ZOSTER infection.

8. NUCLEUS OF FACIAL NERVE :
❏ Fibres of nerve are connected to 4 Nuclei
❏ Situated in lower pons
❏ 1. Motor nucleus of Branchimotor
❏ 2. Superior salivatory nucleus ( parasympathetic )
❏ 3. Lacrimatory nucleus ( parasympathetic )
❏ 4. Nucleus of tractus solitarius ( gustatory )

10. distribution of facial muscles paralysis following upper motor
and lower motor facial nerve palsy

11. Course of facial nerve :

12. ➢ Facial nerve leaves brain stem at Pontomedullary
junction.
➢ Posterior cranial fossa
➢ Internal acoustic meatus
➢ Bony facial canal
➢ Temporal bone
➢ Comes out of stylomastoid foramen.
➢ Crosses styloid process
➢ Divides in to terminal branches.

13. ➢ Three parts :
➢ 1. INTRACRANIAL PART :
○ Pons to internal acoustic meatus (15-17mm)
➢ 2. INTRATEMPORAL PART :
○ internal acoustic meatus to stylomastoid foramen
○ Meatal segment (8-10mm)
○ Labyrinthine segment (4mm)
○ Tympanic membrane/horizontal segment (11mm)
○ Mastoid/Vertical segment (13mm)
➢ 3. EXTRA CRANIAL PART :
○ Stylomastoid foramen to termination

14. BRANCHES OF FACIAL NERVE :
❏ 1. Greater superficial petrosal
nerve
❏ 2. Nerve to stapedius
❏ 3. Chorda tympani nerve
❏ 4. Communicating Branch
❏ 5. Posterior Auricular Nerve
❏ 6. Muscular Branches
❏ 7. Peripheral Branches

15. BLOOD SUPPLY OF FACIAL NERVE:

16. ➢ 1. Anterior-inferior cerebellar artery
○ Supplies in cerebello pontine angle
➢ 2. Labyrinthine artery
○ Branch of Anterior-inferior cerebellar artery
○ Supplies in internal auditory canal
➢ 3. Superficial Petrosal artery
○ Branch of middle meningeal artery
○ Supplies geniculate ganglion
➢ 4. Stylomastoid artery
○ Branch of posterior Auricular artery
○ Supplies mastoid and tympanic segment

17. SURGICAL LANDMARKS OF FACIAL NERVE :
1. Process cochleariformis 1. Cartilaginous pointer
2. Oval Window & Horizontal
Canal
2. Tympanomastoid Suture
3. Short Process of Incus 3. Styloid Process
4. Pyramid 4. Posterior Belly of Digastric
5. Tympanomastoid Suture
6. Digastric Ridge
For middle ear & mastoid surgery For Parotid Surgery

20. ELECTRO DIAGNOSTIC TESTS :
Utilize electrical stimulation to assess nerve function and are
most commonly used.
USES :-
● Differentiate between Neurapraxia & Degeneration of
nerve.
● Helps to predict prognosis and indicate time for surgical
decompression of nerve.
● Detects the degree of dysfunction

21. TESTS ARE :
➢ Minimal Nerve excitability test
➢ Maximal stimulation test
➢ Electroneurography ( ENoG)
➢ Electromyography (EMG)

22. ➢ MINIMAL NERVE EXCITABILITY TEST
PRINCIPLE :
● Transcutaneous electrostimulation of the main trunk first
on the healthy side
● then on the affected side.
● Examiner watches the patient’s face for the first sign of
muscle contraction.
● Significant side difference of stimulation intensity should
indicate poor prognosis.
NOTE :
● Cannot be recommended as prognostic test due to poor
reliability

23. ➢ MAXIMAL STIMULATION TEST
PRINCIPLE :
➔ Setup of Nerve excitability test.
➔ but supramaximal stimulation.
➔ Starts at the main trunk and
➔ follows the branching of the facial nerve.
INTERPRETATION:
● Response is visually graded as equal, decreased or absent.
● Reduced or absent response with maximal stimulation
indicates degeneration and is followed by incomplete
recovery.

24. ➢ ELECTRONEURONOGRAPHY (ENoG) :
PRINCIPLE :
❏ facial nerve is stimulated at the stylomastoid foramen
❏ compound muscle action potentials are picked up by the
surface electrodes.
❏ Supramaximal stimulation is used to obtain maximal action
potentials.
❏ The responses of action potentials of the paralyzed side are
compared with that of the normal side on similar stimulation
and thus percentage of degenerating fibres is calculated

25. ➔ degeneration of 90% occurring in the first 14 days
indicates poor recovery of function.
➔ Faster rate of degeneration occurring in less than 14 days
has a still poorer prognosis.
➔ ENoG is most useful between 4 and 21 days of the onset
of complete paralysis.

26. ➢ ELECTROMYOGRAPHY (EMG) :

27. ● tests the motor activity of facial muscles
● by direct insertion of needle electrodes usually in
orbicular oculi and orbicularis oris muscles
● the recordings are made during rest and voluntary
contraction of muscle.
NOTE :
● Most important 2–3 weeks after onset of the palsy
● because pathologic activity can occur in case of facial
nerve degeneration.
● In the later time course, nEMG is important to detect
reinnervation potentials as signs of reinnervation of
the facial muscles