II. Pathophysiology

  1. Benign Acoustic Nerve tumor typically at cerebellopontine angle
  2. Majority of lesions arise from vestibular branch CN 8

III. 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

IV. 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)

V. Signs

  1. Typically normal exam
  2. Ataxia may be present
  3. Facial weakness or numbness may be present

VI. 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

VII. 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

VIII. Management

  1. Otolaryngology Referral for Surgical Excision
    1. Most otolaryngologists do not preserve Hearing
    2. Hearing preservation technique has 50% success

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