HemeOnc

Acoustic Neuroma

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Acoustic Neuroma, Vestibular Schwannoma

  • Pathophysiology
  1. Benign Acoustic Nerve tumor typically at cerebellopontine angle
  2. Majority of lesions arise from vestibular branch CN 8
  • Epidemiology
  1. Represents 8% of all Brain Tumors
  2. Represents 80% of posterior fossa tumors
  3. Incidence: 1 per 100,000 persons in the United States
  4. Otolaryngologists sued most on missed Acoustic Neuroma
  • Symptoms
  1. Unilateral and persistent Tinnitus beyond 1 month
  2. Gradually progressive unilateral Sensorineural Hearing Loss
    1. Represents only 1-2% of unilateral Hearing Loss causes
  3. Mild episodic Vertigo presenting symptom in 10% of cases
  4. Headache (later finding)
  • Signs
  1. Typically normal exam
  2. Ataxia may be present
  3. Facial weakness or numbness may be present
  • Diagnostics
  1. Pure tone Audiometry (formal testing with audiology)
    1. Asymmetric Hearing Loss may suggest Acoustic Neuroma
      1. Average difference >10 dB over 1 to 8 KHz range (high Test Sensitivity for Acoustic Neuroma)
      2. Average difference >15 dB over 0.5 to 3 KHz range (high Test Specificity for Acoustic Neuroma)
      3. Cheng (2012) Otolaryngol Head Neck Surg 146(3): 438-47 [PubMed]
  2. Other audiology evaluation
    1. Acoustic Reflex Testing
    2. Auditory Brainstem Testing (ABR)
  3. Electronystagmography (ENG)
    1. Abnormal in 50% of cases, but non-specific
  • Imaging
  1. MRI Brain with contrast and including Internal Auditory Canals
    1. Best study for identifying Acoustic Neuroma
    2. Replaces Auditory Brainstem Testing (ABR) for Acoustic Neuroma diagnosis
  • Management
  1. Otolaryngology Referral for Surgical Excision
    1. Most otolaryngologists do not preserve Hearing
    2. Hearing preservation technique has 50% success
  • References
  1. Michels (2019) Am Fam Physician 100(2): 98-108 [PubMed]