return to: Otology - Neurotology

INDICATIONS​

1. Tumor removal is considered one of several options including observation and irradiation (sterotactic radiosurgery). 
2. The natural history of schwannomas is slow but steady growth.
   1. Larger tumors may grow faster (>4 mm/year) and are subject to cystic degeneration.
   2. Smaller tumors, especially in older patients, may grow more slowly (2 mm a year) or may appear quiescent.
3. An urgent indication for removal would be hydrocephalus or ventricular compression.
4. Facial nerve dysfunction, imbalance/vertigo, or desire for hearing preservation would also be indications for proceeding with surgical treatment versus observation.

APPROACH-SPECIFIC INDICATIONS

1. Middle cranial fossa removal
   1. Tumor less than 2 cm, not in contact with brainstem
   2. Servicable hearing
   3. Age less than 60 years
      1. Previous stroke, hydrocephalus, traumatic brain injury, or seizure disorder would be contraindications
      2. Age greater than 60 years should be considered in context of side of surgery (left is higher risk of aphasia), and patient’s general medical condition. The dura is more fragile and more adherent to the skull as the brain ages. Also, the aged brain does not tolerate retraction well.
   4. Also for vestibular nerve section
2. Translabyrinthine removal
   1. Tumor in contact with brainstem
   2. Enlarging tumor in patient over the age of 65 years
   3. Non-servicable hearing
   4. Previous middle-fossa or retrolab
   5. Previous radiation therapy
3. Retrolabyrinthine removal
   1. For select smaller medial tumors that do not extend more than 1/3rd laterally into the internal auditory canal (IAC)
      1. Limited lateral exposure can be increased by going transcrural and sacrificing the posterior semicircular canal
   2. Possible hearing preservation
   3. No cerebellar retraction
4. Retrosigmoid/suboccipital removal
   1. For large medial tumors that do not extend more than 1/3rd laterally into the internal auditory canal (IAC)
      1. Also indicated for vascular loop decompression, vestibular nerve section
   2. Possible hearing preservation
   3. Requires neurosurgical intervention
      1. Cerebellar retraction or resection required
5. Observation
   1. Age over 65 years with stable tumor on serial MRI scanning
   2. Medically unfit for surgery with stable tumor on serial MRI scanning
6. Special Considerations
   1. Type 2 neurofibromatosis with bilateral vestibular schwannomas
      1. In general, preserve acoustic hearing as long as possible, and observe tumors too large for middle fossa or retrosigmoid removal.
      2. Remove smaller tumor and preserve hearing or auditory nerve for cochlear implant.
      3. In general, if we are removing a large tumor with no or sacrificed hearing, we place an auditory brainstem implant at the time of surgery, even if the patient has residual hearing in the contralateral ear.
         1. The best chance for a successful ABI is at the initial surgery when the lateral recess is not scarred.
         2. Two chances at an ABI double your opportunity at getting a good (usable) position.
         3. We consider NF2 as a contraindication to radiosurgery.
   2. Acoustic neuroma in only hearing ear
      1. Remove early if small and either preserve hearing or auditory nerve for cochlear implant
      2. Observe for growth and begin teaching lip reading and sign language for eventual hearing loss
   3. Intracochlear/vestibular tumors
      1. Observe for eventual hearing loss
      2. Perform labyrinthectomy for removal after tumor has destroyed hearing
   4. Facial neuroma
      1. Preserve facial nerve function through debulking tumor and decompressing entire affected segment with initial surgery.
      2. Consider definitive resection and grafting once patient progresses beyond IV/VI House-Brackmann Scale.

PREOPERATIVE PREPARATION

1. History
   1. Auditory symptoms
      1. Hearing loss, tinnitus
      2. Fullness, pressure
   2. Vestibular symptoms
      1. Vertigo, dysequilibrium
      2. Imbalance with quick turns is frequently the only symptom
   3. Always ask the patient if they are right- or left--handed. Speech reception and expression areas are usually in the nondominant temporal lobe.
2. Physical exam
   1. Otoscopic exam is usually normal
   2. Weber and Rinne exam to confirm audiogram
   3. Associated cranial nerve dysfunction (in descending order of likelihood)
      1. Trigeminal (V)
         1. Loss of corneal reflex
         2. Facial numbness
      2. Vagal (X)
         1. Mobility of vocal cords
         2. Mobility of soft palate
         3. Laryngeal sensation
      3. Facial (VII)
         1. Hitzelberger’s sign (anesthesia of medial, posterior, or superior areas of the external auditory canal)
         2. Any twitching, spasm, or decreased function of the facial nerve in a smaller tumor should raise suspicion of a facial neuroma
         3. Rapid eye blink is most sensitive exam for subtle FN dysfunction
      4. Glossopharyngeal (IX): Loss of gag reflex
      5. Abducens (VI): Lateral gaze palsy
3. Ancillary testing
   1. Audiogram
      1. High frequency loss most common pattern
      2. Reduced speech discrimination score on side of tumor common
      3. Recruitment
      4. Roll-over phenomenon
      5. Auditory reflex decay
   2. ABR (for hearing preservation approach)
      1. Used as baseline to monitor hearing intraoperatively
      2. Prolonged absolute V latency
      3. Prolonged I-III and/or I-V latency
   3. Vestibular and cerebellar function testing is usually unnecessary
4. Radiological Evaluation
   1. MRI
      1. T1 with gadolinium fine-cuts in both the axial and coronal planes
         1. Characterization of the tumor
         2. Fat-sat to differentiate from lipoma
         3. Meningioma tend to be based off of petrous ridge, and have a dural tail
         4. Extent and involvement with intracranial structures and vasculature
      2. T2 fast spin echo (CISS or FIESTA) sequencing through IACs only
         1. Look closely for fluid in lateral IAC. A tumor which completely impacts the fundus will be difficult to preserve hearing.
         2. May be adequate screening tool in patients allergic to gadolinium
            1. FLAIR and T2
   2. To assess edema to brainstem, peduncle, and cerebellum in tumors touching or effacing stem
5. Stenvers views of middle cranial fossa floor
   1. Anticipate amount of bone overlying superior semicircular canal
6. CT of temporal bone for retrolabyrinthine approach
   1. Approach requires retrolabyrinthine air cell tract and low jugular bulb
7. Preoperative Evaluation
   1. Labwork
      1. At a minimum: hematocrit/hemoglobin level and PT/PTT
      2. Lytes if patient advanced age, diabetic, or other chronic diseases present
      3. Urine pregnancy on AM of surgery for all women of childbearing age
   2. EKG if indicated by advanced age, CAD risk factors, or underlying heart disease present
   3. Neurosurgery consultation
      1. For retrosigmoid or suboccipital approach
      2. If meningioma expected for resection and reconstruction of dura
      3. If tumor compressing fourth ventricle or hydrocephalus present preoperatively
   4. Medical consultation: Low threshold for active medical problems that will need postoperative in-patient management, if clearance for surgery needed, or if patient currently anticoagulated.

CONSENT FOR SURGERY​

1. Risks inherent to any surgical procedure
   1. Bleeding
   2. infection
   3. scar formation
   4. alopecia
   5. skin anesthesia or dysesthesia
2. Risks inherent to any craniotomy
   1. stroke
   2. paralysis
   3. seizure
   4. death
3. Risks of anesthesia
4. Risks specific to patient
   1. Subtotal tumor removal with potential for recurrence
   2. Facial nerve injury
      1. Potential nerve grafting using either the greater auricular nerve or sural nerve
   3. Hearing loss
      1. subtotal or profound
      2. expected after translabyrinthine approach
      3. tinnitus that may be permanent
   4. Prolonged imbalance
      1. peripheral
      2. central
   5. CSF leak with the potential for meningitis
      1. Need for lumbar drain
      2. Need for revision surgery
5. Risks specific to middle fossa
   1. Expressive and/or receptive aphasia if nondominant temporal lobe
   2. Intracranial hemorrhage
   3. Seizure
   4. trismus
   5. temporalis atrophy
   6. delayed facial paresis
6. A risk specific to translabyrinthine approach would include the definite need for abdominal fat to close defect.
7. A risk specific