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Facial Nerve Schwannoma
Built from Haynes-Glasscock-Shambaugh Surgery of the Ear, Seventh Edition
What’s inside
10 sections · 130 slides
Overview
- Scope of this presentation
Nature and epidemiology
- Definition of facial nerve schwannoma
- Early history of facial nerve tumours
- Modern shift toward functional preservation
- Incidence relative to other skull base tumours
- Demographic profile and NF2 association
Histopathology
- Growth pattern on the parent nerve
- Epineurium and its surgical implication
- Distribution of nerve fibres within the tumour
- Skip lesions and dumbbell configuration
- Histological patterns and immunohistochemistry
Anatomical distribution
- Course of the facial nerve from pons to parotid
- Frequency of segment involvement
- Less commonly involved sites
- Rate of involvement of each facial nerve segment
Clinical evaluation
- Presenting symptoms
- Effects of large cerebellopontine angle tumours
- Reported frequency of clinical manifestations
- Clinical manifestations
- Sensorineural hearing loss
- Conductive hearing loss
- Facial nerve symptoms at presentation
- Distinguishing FNS from Bell's palsy
- House-Brackmann grade at presentation
- Site of tumour and risk of facial dysfunction
- Mechanism of weakness in bony-confined segments
- McMenomey series on site and facial weakness
- Otoscopy and physical examination
- Otoscopic appearance of middle ear and mastoid tumours
- Audiometry and electrical testing
- Role and hazards of biopsy
Imaging
- Indications for imaging the facial nerve
- MRI features of facial nerve schwannoma
- MRI of a tumour spanning the CPA, IAC and geniculate ganglion
- Pitfalls of enhancement comparison
- CT features of facial nerve schwannoma
- CT of fallopian canal widening in labyrinthine and mastoid tumours
- Radiological hallmark of the diagnosis
Differential diagnosis
- Differential diagnosis overview
- Intracanalicular and CPA tumours
- Why the misdiagnosis is so common
- CPA tumour presumed vestibular before subtotal resection
- Meningioma of the internal auditory canal
- Meningioma mimicking multi-segment involvement
- Labyrinthine and geniculate segment appearances
- Geniculate ganglion tumours and GSPN spread
- Geniculate autodecompression with a tight meatal foramen
- Geniculate ganglion haemangioma versus schwannoma
- Tympanic segment tumours
- Other middle ear mimics
- Mastoid segment tumours
- Traumatic neuroma of the facial nerve
- Intraneural perineurioma
- Intraparotid and extracranial tumours
Management
- Evolution of management strategy
- Spectrum of treatment options
- Factors driving the treatment decision
- Simplified management algorithm
- Candidates for observation
- Documented trend toward observation
- Observation outcomes: Perez and Liu series
- Observation outcomes: Yang and Mayo Clinic series
- What the observation data mean
- Traditional trigger for surgical intervention
- Rationale for stereotactic radiosurgery
- McRackan meta-analysis of radiosurgery outcomes
- Carlson and Moon radiosurgery series
- Mechanism of facial palsy after radiosurgery
- Serial MRI after radiosurgery for a CPA tumour
- North American Gamma Knife Consortium series
- Japanese multicentre Gamma Knife series
- Indications and contraindications for radiosurgery
- Indications for microsurgery
- Choosing a surgical approach
- Transmastoid approach
- Combined transmastoid and middle fossa approach
- Approaches when hearing is not serviceable
- Retrosigmoid approach
- Parotid approach
- Pedunculated tumour on the main trunk after parotidectomy
- Gross total resection with reinnervation
- Outcomes after resection and grafting
- Reconstructive choices in the Mayo series
- Facial nerve decompression
- Technique of decompression
- Selecting patients for decompression
- Decompression compared with observation
- Rationale and risks of subtotal resection
- Technique of subtotal resection
- Outcomes after subtotal resection
- Dilemma of complete palsy after debulking
- Gross total resection with nerve preservation
- Outcomes with nerve preservation techniques
- Fascicle preservation in the posterior fossa
- Initial management by presentation
- Observation period within the algorithm
- Acute facial paralysis during observation
- Delaying resection until HB IV
- Timing of nerve repair once HB IV is reached
- Monitoring for subclinical denervation
- Predicting recovery after nerve-preserving surgery
- Unexpected facial nerve schwannoma found at surgery
- Managing an intraoperatively diagnosed tumour
Facial reanimation
- Principles of facial reanimation
- Interposition nerve grafting
- Coaptation techniques and their reliability
- Nerve transfer and muscle transfer
- Eye care in facial paralysis
Summary and references
- Key points on diagnosis
- Key points on management
- References
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- References (continued)
- Haynes-Glasscock-Shambaugh Surgery of the Ear, Seventh Edition
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