Vestibular schwannoma

Disease Description (Causes and Symptoms)

• Definition: A benign tumor originating from Schwann (neurilemmal) cells of the vestibular nerve (cranial nerve VIII) (vestibular schwannoma, formerly called acoustic neuroma). It usually begins in the internal auditory canal and grows toward the cerebellopontine angle as it enlarges.

• Causes/Pathophysiology: The exact cause is unknown. It may occur bilaterally in patients with neurofibromatosis type 2 (NF2), and the tumor causes symptoms by compressing the vestibular nerve through Schwann cell proliferation.

• Main symptoms:

  • Unilateral (usually) progressive sensorineural hearing loss (decreased hearing) and reduced speech discrimination
  • Tinnitus
  • Vertigo (dizziness) and balance problems (especially when the tumor becomes large)
  • Rarely, onset as sudden hearing loss
  • As the tumor progresses: facial sensory changes (trigeminal nerve symptoms), facial paralysis, dysphagia, speech changes, gait ataxia, and headache, vomiting, and hydrocephalus due to brainstem compression

• Epidemiology and clinical features (for reference): Occurs mainly in adults (more common after age 30), with a slightly higher incidence in women than in men. NF2 should be suspected in children or young patients with bilateral tumors.

Treatment Methods and Precautions

• Treatment principles: Observation, radiosurgery, or microsurgery (resection) is selected according to symptoms, tumor size and growth rate, and the patient’s age and general condition.
• Observation (regular follow-up): For small, asymptomatic tumors or in older adults, MRI and hearing tests are performed periodically (e.g., every 6–12 months); if there is no growth, conservative management is continued.
• Radiosurgery (Gamma Knife, etc.): Effective for suppressing tumor growth in small to medium-sized tumors (or residual/recurrent tumors). Its advantages include a high rate of facial nerve preservation. Short- and long-term post-radiation changes (inflammation and temporary neurological deficits) may occur.
• Surgical removal: Complete resection can be curative. The surgical approach is selected according to whether hearing preservation is possible, as well as the tumor’s size and location.
  • Middle fossa approach: Used to preserve hearing in small, limited tumors within the internal auditory canal
  • Retrosigmoid/suboccipital approach: Applicable to tumors of various sizes, with a possibility of hearing preservation
  • Translabyrinthine approach: Advantageous for facial nerve preservation when hearing preservation is impossible
• Postoperative and supportive care during conservative treatment: Hearing rehabilitation such as vestibular rehabilitation, hearing aids, CROS, BAHA, and cochlear implants (considered when the cochlear nerve is preserved).
• Medication: Short-term steroid use may be considered when acute sudden hearing loss occurs concurrently (depending on the clinical situation).
• Complications and precautions: Facial nerve paralysis, hearing loss, cerebrospinal fluid leak (CSF leak), infection (meningitis), bleeding, brainstem or cerebellar injury, and hydrocephalus. Because changes in neurological function may occur after surgery or radiation, the risks and benefits should be discussed when selecting a treatment method.
• Prognosis: Varies depending on tumor size, treatment method, timing of treatment, and the degree of nerve preservation during surgery. Small tumors can be expected to have a good prognosis with conservative management or radiosurgery. Large tumors carry increased surgical risks and a greater possibility of nerve injury.

Pre-Appointment Checklist (Items to Prepare and Example Questions)

• Items/materials to prepare or bring:
  • List of medications currently being taken (especially anticoagulants, antiplatelet agents, steroids, etc.)
  • Previous hearing tests (pure-tone audiometry and speech discrimination) and copies of recent MRI/CT images (if possible, the original films or digital files)
  • A record of when symptoms began and how they have progressed (when they started, gradual/acute, unilateral/bilateral)
  • A record of the type and frequency of dizziness and its effects on daily life, such as sleep and driving
  • Existing neurological problems (facial paralysis, sensory changes, etc.) and family history (especially whether NF2 may be involved)
• Example questions for the pre-appointment checklist (to record yourself):
  • When did the hearing loss begin? Is it only on one side?
  • Do you have tinnitus (ringing in the ears)? What is it like (continuous/intermittent)?
  • What type of dizziness is it (rotational/non-rotational), and how often does it occur?
  • Have you recently had headaches, nausea/vomiting, unsteady gait, or facial sensory changes?
  • Does anyone in your family have a similar condition (NF2, multiple schwannomas, etc.)?

General Example Questions to Ask the Doctor

• What is the first diagnostic test recommended for this patient? Should I have an MRI right away?
• What are the advantages and disadvantages of the treatment options for our tumor’s size and location (observation vs. radiosurgery vs. surgery)?
• What recovery period and possible complications should be expected after surgery or radiation therapy?
• How likely is hearing preservation? If hearing loss occurs, what rehabilitation options are available (hearing aids, BAHA, cochlear implants, etc.)?
• Is NF2 genetic testing (genetic counseling) necessary if there are bilateral lesions or if the patient is young?

Examples of Disease-Specific Questions (1–2)

• What is the size of my tumor (is it limited to the internal auditory canal, or does it protrude into the CPA), and what is its recent growth rate (based on comparison of MRI results)?
• Considering my current hearing test and speech discrimination results, is a surgical approach that prioritizes hearing preservation possible? If not, why?