Facial nerve decompression

1. Facial Nerve Decompression
Dr.Mamoon Ameen

2. INTRODUCTION
• Decompression : opening the bony canal and nerve sheath to release pressure and reduce
compression on nerve fibers.
• The goal of decompression is to improve blood circulation and minimize damage to distal
nerve fibers.
• The facial nerve is the longest nerve that travels in a bony canal with a complex course and
high susceptibility to injury
• lack of expansion room in a rigid bony canal, potentially leading to severe nerve
damage and even necrosis and fibrosis

3. INTRODUCTION
• Facial paralysis causes significant functional and aesthetic defects that often lead to
great psychosocial distress
• The goal of management in patients with facial paralysis of any etiology is to
maximize functional recovery and minimize cosmetic deformity
• When complete paralysis is due to either anatomic discontinuity or irreversible
neural degeneration, the facial nerve requires repair or decompression for the most
optimal functional and aesthetic results

4. ANATOMY
• Motor root: 7000 axons
• Sensory root (Nervus intermedius / Wrisberg): 3000
axons
• Motor: facial muscles
• Secretomotor: lacrimal, submandibular, sublingual
• Taste: anterior 2/3rd of tongue
• Sensory: Post-aural / concha / ext. auditory canal

5. ANATOMY
SEGMENTS OF FACIAL NERVE
1. Intra-cranial (12 mm): Brain stem to entry into IAC
2. Meatal (10 mm): Within Internal Auditory Canal
3. Labyrinthine (4 mm): Fundus of I.A.C. to Geniculate
gangl.
4. Tympanic (11 mm): Geniculate ganglion to pyramid
5. Mastoid (13 mm): Pyramid to stylomastoid foramen
6. Extra-temporal (15 mm): S.M. foramen to pes
anserinus

6. ANATOMY

7. Anatomy

8. ANATOMY

9. SURGICAL LANDMARKS
Cochleariform process: lies 1 mm inferior to geniculate
ganglion at anterior end of tympanic segment.
Cog: bony ridge hanging from tegmen tympani lies 1
mm above & posterior to cochleariform process.
Incus short process: 2 mm below lies external genu
Lateral Semicircular Canal: 2 mm Antero-Infero-Medial
lies external genu
Oval window: 1 mm above lies external genu

10. SURGICAL LANDMARKS
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
Groove between mastoid & bony E.A.C. meatus: bisected
by facial nerve
Tragal pointer: 1 cm antero-infero-medial is facial nv
Root of styloid process: lateral lies facial nerve
Superior border of posterior belly of digastric: superior &
parallel lies facial nerve

11. ETIOLOGY OF FACIAL NERVE PALSY
1. Idiopathic (55%): Bell’s palsy,
2. Temporal bone trauma (25%): Road traffic accident
3. Infection (10%): C.S.O.M., Herpes Zoster oticus
Malignant otitis externa,cholesteatoma
4. Neoplasm (5%): Parotid tumors, Acoustic Neuroma,
Glomus tumors, Malignancy of ear
5. Congenital (4%): Moebius syndrome ,Melkersson Rosenthal syndrome
6. Iatrogenic : Mastoidectomy, Parotid surgery
7. Metabolic (rare): Diabetes mellitus, Hypertension

12. NERVE INJURY
STRUCTURE OF NERVE

13. Nerve injury

14. HOUSE-BRACKMANN FACIAL NERVE GRADING SYSTEM
Nerve injury

16. TOPO-DIAGNOSTIC TESTS
• Audiometry: cochlear nerve function
• Vestibulometry: vestibular function
• Schirmer’s test: Greater Superficial Petrosal Nerve
• Stapedial reflex test: Nerve to stapedius
• Electrogustometry: Chorda tympani
• Submandibular salivary flow: Chorda tympani
• Examination for terminal facial nerve branches

18. Electrical testing
• Primary diagnostic modality for surgical decision making
• Estimate the severity of nerve injury ,Prognosis
• Most reliable and objective tests are ENoG and EMG
• Of value only with complete facial paralysis

19. Electro-neuronography
• Measures the amount of intact axons relative to the
healthy side
• Useful between 4 and 21 days of onset of complete
paralysis
• Degeneration > 90% correlated with poor prognosis

20. Electromyography
• Needle electrodes placed within the facial musculature
measures spontaneous and voluntary electrical activity in
the facial muscle
• Assessing the muscle denervation and reenervation
• adjunct to ENoG if surgical decompression is being
considered
• polyphasic action potentials indicate muscle reinnervation
• fibrillation potentials detected 2 to 3 weeks after injury
indicate significant muscle denervation and poor recover

22. FACIAL NERVE DECOMPRESSION
• Performed in severe cases when the facial nerve is seriously deteriorating
• Patient are at high risk of permanent paralysis and have a poor prognosis without
aggressive intervention
• To be effective surgery must be performed within 2 weeks of the onset of symptoms

23. PREOPERATIVE PLANNING
• ENOG :10% or less muscle function on affected side compared with normal
side from 3-14 days post complete paralysis
• EMG : absence of motor unit action potential
• HRCT : trauma ,otitis media.
• MRI : suspicion of underlying tumor
• Audiometric tests : associated hearing loss , surgical approach ,

24. Site to be explored
Based on causes of facial paralysis and suspected site of injury
• Bells palsy : the labyrinthine segment and perigeniculate region are decompressed
via a middle fossa approach.
• Acute or chronic otitis media : the mastoid and tympanic segments are explored
• Canal wall down mastoidectomy :cholesteatoma involving facial nerve
• Intraoperative injury :directed to the site of injury

25. SURGICAL APPROACHES
Selection of the surgical approach is determined by the location of the facial nerve
injury and hearing status in the affected ear
• Trans-mastoid approach
• Middle cranial fossa approach
• Translabyrinthine approach

26. TRANSMASTOID APPROACH
Indication
• Tumors limited to mastoid and tympanic segment
• Longitudinal fracture limited to mastoid segment
• AOM,COM involving tympanic segment and mastoid segment
Limitations
• Limited access to geniculate ganglion
• No access to labyrinthine segment

27. TRANS-MASTOID APPROACH

31. The circumference of the facial nerve
should be exposed for 180 degrees
along its posterior and superior surface,
between the lateral semicircular canal
and the stylomastoid foramen

33. • The junction of the facial nerve and
geniculate ganglion is reached with
further anterior and medial
dissection under the head of the
malleus

34. • Once the fallopian canal in the tympanic and mastoid segments has been exposed,
any residual impinging bony spicule is removed.
• The nerve sheath is opened at the site of injury and for a short distance proximal
and distal to the site of injury to assess the severity of injury to the fascicles.
• If the fascicles are intact, the decompression procedure is complete.
• If more than 50% of the nerve fascicles have been violated or the nerve is
completely transected, primary neurorrhaphy or cable grafting is indicated.

35. • The postauricular wound is closed in layers
• Mastoid dressing is applied to the operated ear for 24 hours.

36. Complications
• Further surgical trauma to the facial nerve
• Hearing loss (either conductive or sensorineural),
• Vertigo
• CSF leak
• Wound infection.

37. MIDDLE FOSSA APPROACH
Exposure from IAC to tympanic segment (for intracanalicuar and
labyrinthine segments)
Indication:
A) Bells palsy
B) Longitudinal temporal bone fractures
Advantages
A)No hearing impairment ,even geniculate ganglion and tympanic segment
can be decompressed
b)Combined with retrolabyrinthine ,transmastoid for enttire facial nerve
exposure

38. • 6x8cm trap door incision above ear (
• 4x4 cm temporalis fascia graft
harvested
• Anterinferior based temporalis
musculo perisosteal flap elevated

39. • A bone flap centered over zygoma elevated,
taking care middle meningeal artery on inner
table
• Dura elevated from posterior to anterior till
petrous ridge, arcuate eminence, meatal
plane, and GSPN Anteriorly.

40. • Blue lining of superior semicircular canal seen
• Anterior to it IAC opened with 7th nerve anterosuperiorly (BILLS BAR
FORMS LATERAL BOUNDARY OF MEATAL FORAMEN)
• Labrynthine segment followed laterally till geniculate ganglion.
• Tegmen tympani removed
• Tympanic segment blue lined and final layer of bone removed with
elevator and decompressed

41. After the craniotomy flap (CT) has been created in a
left temporal bone, a septal raspatory is carefully used
to separate the bony flap from the middle fossa dura.
The craniotomy is successfully elevated from the middle fossa
dura (MFD).

42. Elevation of the middle fossa dura (MFD) from the middle
fossa plate (MFP)
As dural elevation advances anteriorly, the middle meningeal
artery (MMA) is identified next.AE Arcuate
eminence, MFD Middle fossa dura, MFP Middle fossa plat

43. The greater petrosal nerve (GPN) is identified
next. AE Arcuate eminence, MMA Middle meningeal
artery
The middle fossa retractor is fixed at the petrous
ridge (PR). AE Arcuate eminence, GPN Greater petrosal
nerve, M Middle meningeal artery

44. The expected location of the internal auditory
canal (IAC). The bar-shaded areas are the locations
for drilling.
Identification of the internal auditory canal is started by drilling
between the arcuate eminence (AE) and the expected level of
the internal auditory meatus (*) using a large burr. GPN Greater
petrosal nerve

45. The dura of the internal auditory canal (IAC) can be
seen through the thin bone covering. The arcuate
eminence (AE) and the cochlea (C) have been well
skeletonized to gain the maximum space. GPN Greater
petrosal nerve
Further drilling identifies the posterior fossa
dura (PFD) under the thin bone covering. AE Arcuate
eminence, C Cochlea, GPN Greater petrosal
nerve, IAC Internal auditory canal, MFD Middle
fossa dur

46. The bony covering of the posterior fossa dura (*) is
being removed
The bony covering of the internal auditory canal and the
posterior fossa dura anterior to the canal (*) is being
removed. AE Arcuate eminence, C Cochlea

47. The dura of the internal auditory canal (IAC) is
being opened.
The acousticofacial bundle (AFP) can be seen within the
opened internal auditory canal.

48. The dura of the internal auditory canal has been further
removed. Bill’s bar (BB) can be seen at the level of the
fundus. AE Arcuate eminence, C Cochlea, FN Facial
nerve within the internal auditory canal, GPN Greater
petrosal nerve, L Labyrinthine segment of the facial
nerve, SVN Superior vestibular nerv
At higher magnification, the relationship at the fundus can be
better appreciated. AE Arcuate eminence, BB Bill’s
bar, C Cochlea, FN(iac) Internal auditory canal segment of the
facial nerve, GG Geniculate ganglion, GPN Greater petrosal
nerve, L Labyrinthine segment of the facial
nerve, SVN Superior vestibular nerve

50. • Epitympanic defect covered with temporalis fascia.
• The roof of the IAC is sealed with a small abdominal fat graft.
• The skin flap is then reapproximated in two layers without the use of any drain
• A mastoid dressing is placed over the operated ear for 3 days postoperatively

51. Complications
• Sensorineural hearing loss
• Vertigo
• Edema of the temporal lobe
• Subdural hematoma
• CSF leak
• Meningitis.
• brainstem and cerebellar infarction
• Injury to AICA

52. TRANSLABYRINTHINE APPROACH
The translabyrinthine approach can be utilized for decompression of the entire
intratemporal course of the facial nerve in cases where cochleovestibular function is
already lost
Indication
• Transverse temporal bone fracture,
• Extensive facial neuroma, or a
• Large congenital cholesteatoma that extends into the IAC.
Advantages
• Entire nerve is exposed using a single approach

53. • incision is made 3 cm behind the postauricular
crease and carried inferiorly over the mastoid
tip.
• A portion of the occipital bone posterior to the
sigmoid sinus also should be exposed.
• An extended complete mastoidectomy is
performed.
• The bone over the sigmoid sinus is removed,
along with 0.5 to 1.0 cm of bone posterior to
this structure.

54. • The facial recess is opened
• Inferior to the posterior semicircular canal, bone is removed, exposing the jugular bulb,
posterior fossa dura, and endolymph
• Bone is removed 180 degrees around the internal canal
• The dura over the IAC and cerebellar plate can be opened to expose the
cerebellopontine cistern and brainstem
• Closure is accomplished with a 4- × 4-cm piece of temporalis fascia covering the dural
defect and draped over the aditus to separate the mastoid from the middle ear
• Abdominal fat is harvested and used to obliterate the mastoid space.

59. THANK YOU