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. 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 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 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 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 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 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 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 Motor root: 7000 axons Sensory root (Nervus intermedius / Wrisberg): 3000 axons Sensory root (Nervus intermedius / Wrisberg): 3000 axons Motor: facial muscles Motor: facial muscles Secretomotor: lacrimal, submandibular, sublingual Secretomotor: lacrimal, submandibular, sublingual Taste: anterior 2/3rd of tongue Taste: anterior 2/3rd of tongue Sensory: Post-aural / concha / ext. auditory canal 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 Malignant otitis externa,cholesteatoma 4. Neoplasm (5%): Parotid tumors, Acoustic Neuroma, Glomus tumors, Malignancy of ear 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 Audiometry: cochlear nerve function Vestibulometry: vestibular function Vestibulometry: vestibular function Schirmer’s test: Greater Superficial Petrosal Nerve Schirmer’s test: Greater Superficial Petrosal Nerve Stapedial reflex test: Nerve to stapedius Stapedial reflex test: Nerve to stapedius Electrogustometry: Chorda tympani Electrogustometry: Chorda tympani Submandibular salivary flow: Chorda tympani Submandibular salivary flow: Chorda tympani Examination for terminal facial nerve branches Examination for terminal facial nerve branches

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

19. Electro-neuronography Measures the amount of intact axons relative to the healthy side Measures the amount of intact axons relative to the healthy side Useful between 4 and 21 days of onset of complete paralysis Useful between 4 and 21 days of onset of complete paralysis Degeneration > 90% correlated with poor prognosis 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 Needle electrodes placed within the facial musculature measures spontaneous and voluntary electrical activity in the facial muscle Assessing the muscle denervation and reenervation Assessing the muscle denervation and reenervation adjunct to ENoG if surgical decompression is being considered adjunct to ENoG if surgical decompression is being considered polyphasic action potentials indicate muscle reinnervation polyphasic action potentials indicate muscle reinnervation fibrillation potentials detected 2 to 3 weeks after injury indicate significant muscle denervation and poor recover 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 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 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 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 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 EMG : absence of motor unit action potential HRCT : trauma,otitis media. HRCT : trauma,otitis media. MRI : suspicion of underlying tumor MRI : suspicion of underlying tumor Audiometric tests : associated hearing loss, surgical approach, 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. 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 Acute or chronic otitis media : the mastoid and tympanic segments are explored Canal wall down mastoidectomy :cholesteatoma involving facial nerve Canal wall down mastoidectomy :cholesteatoma involving facial nerve Intraoperative injury :directed to the site of injury 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 Trans-mastoid approach Middle cranial fossa approach Middle cranial fossa approach Translabyrinthine approach Translabyrinthine approach

26. TRANSMASTOID APPROACH Indication Tumors limited to mastoid and tympanic segment Tumors limited to mastoid and tympanic segment Longitudinal fracture limited to mastoid segment Longitudinal fracture limited to mastoid segment AOM,COM involving tympanic segment and mastoid segment AOM,COM involving tympanic segment and mastoid segmentLimitations Limited access to geniculate ganglion Limited access to geniculate ganglion No access to labyrinthine segment 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 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. 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. 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 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. 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 The postauricular wound is closed in layers Mastoid dressing is applied to the operated ear for 24 hours. Mastoid dressing is applied to the operated ear for 24 hours.

36. Complications Further surgical trauma to the facial nerve Further surgical trauma to the facial nerve Hearing loss (either conductive or sensorineural), Hearing loss (either conductive or sensorineural), Vertigo Vertigo CSF leak CSF leak Wound infection. 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 ( 6x8cm trap door incision above ear ( 4x4 cm temporalis fascia graft harvested 4x4 cm temporalis fascia graft harvested Anterinferior based temporalis musculo perisosteal flap elevated Anterinferior based temporalis musculo perisosteal flap elevated

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

40. Blue lining of superior semicircular canal seen Blue lining of superior semicircular canal seen Anterior to it IAC opened with 7th nerve anterosuperiorly (BILLS BAR FORMS LATERAL BOUNDARY OF MEATAL FORAMEN) Anterior to it IAC opened with 7th nerve anterosuperiorly (BILLS BAR FORMS LATERAL BOUNDARY OF MEATAL FORAMEN) Labrynthine segment followed laterally till geniculate ganglion. Labrynthine segment followed laterally till geniculate ganglion. Tegmen tympani removed Tegmen tympani removed Tympanic segment blue lined and final layer of bone removed with elevator and decompressed 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. Epitympanic defect covered with temporalis fascia. The roof of the IAC is sealed with a small abdominal fat graft. 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 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 A mastoid dressing is placed over the operated ear for 3 days postoperatively

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

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