Facial nerve

2.  ANATOMY
 INTRODUCTION
 COURSE OF FACIAL NERVE
 BRANCHES
 CAUSES OF FACIAL NERVE PARALYSIS
AND THEIR MANAGEMENT

3.  VII Cr Nv ; Mixed Nerve
 10,000 fibers- Motor , Sensory , Parasympathetic fibers
 Motor root – 7000, Special Visceral Efferent Fibers
 Sensory & Parasympathetic – 3000 carried by “NERVUS
INTERMEDIUS” (Nv of Wrisberg)
 NI consists of – General Visceral Efferent
– Special Visceral Afferent
– Somatic Afferent

4.  3 nuclei
1) Motor nucleus –
lower Pons below 4th
ventricle
2) Superior salivatory
nucleus – dorsal to
motor Nucleus
3) Nucleus of tractus
solitarius– medulla
oblongata

6.  From brainstem to fundus of IAM
 Length 24mm
 FN crosses CP angle with 8th CN &
NI
 Devoid of epineurium
 Thin layer of pia mater
 Surg imp :
1) Iatrogenic trauma in CP angle
tumour surgery
2) Difficult to identify in schwannoma
(no connective tissue)

7.  From fundus to
Stylomastoid foramen
 Length – 28 to 30 mm
 “Fallopian canal”
 Longest bony canal

8.  Enters in ant sup
segment of IAC
 Length 5 – 12 mm
 Crista falciformis
 Bills bar
 No separate sheath
 Shares with NI & 8th CN

9.  Narrowest(0.68) &
Shortest(3-5mm)
 No anastomosing
arteries
 Periostium is thicker
 Postero-Superior to
cochlea
 Antero-Medial to SSCC
 Distal end – Geniculate
ganglion;1st genu

10.  Surgical importance:
1) Anatomical bottle neck – ischemia in oedema
2) Part most vulnerable for ischemia (no arterial
anastomosis)
3) Temporal bone # - MC injured
 Geniculate ganglion:
 Bipolar gang cells
 Afferent input – somatic & special visceral afferents
 Secretomotor Fibers to lacrimal gland (without
synapse)

11.  Horizontal segment
 From GG to 2nd genu
 Length – 8 to 11mm
 Lies beneath LSCC &
above OW
 above & medial to
“Processus cochleariformis”

12.  Nerve lies lateral &
posterior to Pyramidal
process
 Creats 2 recesses
1. Facial recess (lat)
2. Sinus tympani(med)
 2nd genu

13.  Surgical importance:
 Processus
cochleariformis(consistant
landmark)
 Imp landmark for 2nd genu –
-LSCC
-Pyramidal eminence
-B/w short process of
incus(L) & LSCC(M)

14.  Vertical Segment
 From 2nd Genu To SMF
 Longest (13mm)
segment
 Landmark – “Digastric
Ridge”

15.  From SMF to terminal
branches
 Runs in substance of
parotid
 Main trunk divides
- upper temperofacial
- lower cervicofacial
 “Pes anserinus”
 Superficial to
Retromandibular Vein

16.  Intra temporal region :
1) GSPN
2) Nerve to stapedius
3) Chorda tympani
4) Sensory auricular
branch

17.  From GG
 2 types of fibers
 Pregang para symp –
Pterygopalatine gang.
 Post gang – lacrimal G
 Sensory fibers to
nasal & palatine glands
 Joins deep petrosal N
– N to pterygoid canal

18.  NERVE TO STAPEDIUS
 Arises 6mm above SMF
 Supply stapedius muscle
 SENSORY AURICULAR BRANCH
 Joins auricular branch of vagus
 Supply retro auricular groove & concha.

19.  4mm above SMF
 Lateral & anterior to Facial Nerve
 Lateral to Long Process of incus & medial to malleus
 2 types of fibers
1. Pre Ganglionic Parasympathetic – submandibular
gland
 Post Ganglionic – submandibular & subligual Glands
2. Special sensory – anterior 2/3rd of tongue

20.  Extra temporal region
1) Posterior auricular Nerve (occipito
frontalis & muscles of pinna)
2) Muscular Branches (posterior belly of
digastric & stylohyoid)

22. There are three imp. issues when confronted with
facial nerve paralysis:
 The cause
 The site of lesion
 The prognosis
A. TOPODIAGNOSTIC TESTING
B. ELECTROPHYSIOLOGY

23. TEST NERVE BRANCH
ASSESSED
1. SCHIRMER TEST Greater superficial petrosal
nerve
2. STAPEDIAL REFLEX Nerve to stapedius muscle
3. ELECTROGUSTROMETRY Chorda tympani
4. SALIVARY FLOW
TESTING
Chorda tympani

24. 1. MINIMAL NERVE EXCITABILITY TEST
2. MAXIMAL STIMULATION TEST (MST)
3. ELECTRONEURONOGRAPHY (ENoG)
4. ELECTROMYOGRAPHY (EMG)

25. 1. BIRTH
 Moulding
 Forceps delivery
 Dystrophia myotonia
 Moebius syndrome {facial diplegia a/w other cranial
NV defects}
2. TRAUMA
 Basal skull fracture
 Facial injuries
 Barotruma {scuba diving , altitude paralysis}

26. 3. NEUROLOGICAL
 Opercular syndrome (cortical lesion in facial motor
area)
 Millard – Gublar syndrome (abducens palsy with
contralateral hemiplegia d/t lesion in base of pons )
4. INFECTION
 Otitis externa
 Otitis media , cholesteatoma
 Mastoiditis
 Herpes zoster cephalicus (Ramsay Hunt Syndrome)
 Encephalitis
 Others

27. 5. METABOLIC
 Diabetes mellitus
 Hyperthyroidism
 Pregnancy
 Hypertension
 Acute porphyria
5. NEOPLASTIC
 VII th nerve tumour
 Glomus jugulare
 Meningioma
 Schwannoma
 Others (nf2 , hemangioma, glioma)

28. 7. TOXIC
 Thalidomide
 Carbon monoxide
 Tetanus
 Diphtheria
8. IATROGENIC
 Mandibular block anesthesia
 Dental procedures
 Parotid surgery
 Mastoid surgery

29. 9. IDIOPATHIC
 Bell’s palsy
 Melkersson – Rosenthal syndrome (recurrent
alternating facial palsy, furrowed tongue, faciolabial
oedema)
 Hereditary hypertrophic neuropathy (charcot marie
tooth disease)
 Temporal arteritis
 Thrombotic thrombocytopenic purpura
 Myasthenia gravis
 Sarcoidosis (Heerfordt Syndrome- uveoparotid
fever)

30.  Diagnostic criteria-
 Paralysis or paresis of all muscle groups on one side of
the face;
 Sudden onset;
 Absence of signs of central nervous system disease;
 Absence of signs of ear or CPA disease.
 Aetiology –
 Microcirculatory failure of vassa nervosum
 Ischaemic neuropathy
 Infectious (HSV-1,HSV-2,VZV,EBV,Influenza B)
 Genetic
 Immunologic

31.  TREATMENT
 STEROIDS
 Prednisolone -1mg/kg for 5 days f/b a ten day taper.
 ANTIVIRAL DRUGS
 Oral Acyclovir – (200-400 mg five times a day) for ten
days.

32.  Definition –
 peripheral facial nerve palsy accompanied by
 an erythematous vesicular rash on the ear (zoster oticus)
or in the mouth.
 Mechanism -
 reactivation of the latent VZV in the geniculate
ganglion
 Persistent excruciating Pain and SNHL

33.  TREATMENT-
If started within three days of onset = significant
improvement
 Prednisolone - 1mg/kg for 5 days f/b a ten
day taper
 Intravenous acyclovir (250 mg three times
daily) or oral acyclovir (800 mg five times
daily)

34.  LONGITUDINAL FRACTURE
 More common (80%)
 Parietal blow
 Conductive hearing loss
 CSF otorrhoea
 Facial paralysis less (20%). Delayed onset
 TRANSVERSE FRACTURE
 Less common (20%)
 Occipital blow
 SNHL
 Facial paralysis more common (50%). Immediate
onset
 MIXED

35.  TREATMENT
 Surgical exploration- goals:
a. To decompress the nerve
b. To remove bony fragments that impinge on nerve.
c. To re establish continuity in case of transaction
1. Early post injury stage–
 Acute onset incomplete palsy without progression –
Medical Treatment
 Acute complete paralysis /incomplete paralysis that
progresses to complete paralysis – Surgical
Exploration (ENoG shows>90%denervation within 6
days of onset)

36. 2. Late post injury stage –
 Late Exploration-
• End to end anastomosis
• Interposition grafting (cable grafts- ipsilateral great
auricular nv, sural nv, medial antebrachial cutaneous
nvs)
• Rerouteing
• Reinnervation – hypoglossal facial anastomosis, cross
facial nerve grafting (using a sural nv graft)
 Static or Dynamic Facial Reanimation
Procedures (if EMG findings suggest long term
denervation)
 Temporalis muscle transfer
 Masseter muscle transfer

37. Otology could be a dull way of life without the 7th
cranial N arrogantly swerving through the temporal
bone to the muscles of facial expression
“JOHN GROVES”