II. Pathophysiology
- Benign Acoustic Nerve tumor typically at cerebellopontine angle
- Majority of lesions arise from vestibular branch CN 8
III. Epidemiology
- Represents 8% of all Brain Tumors
- Represents 80% of posterior fossa tumors
- Incidence: 1 per 100,000 persons in the United States
- Otolaryngologists sued most on missed Acoustic Neuroma
IV. Symptoms
- Unilateral and persistent Tinnitus beyond 1 month
- Gradually progressive unilateral Sensorineural Hearing Loss
- Represents only 1-2% of unilateral Hearing Loss causes
- Mild episodic Vertigo presenting symptom in 10% of cases
- Headache (later finding)
V. Signs
- Typically normal exam
- Ataxia may be present
- Facial weakness or numbness may be present
VI. Diagnostics
- Pure tone Audiometry (formal testing with audiology)
- Asymmetric Hearing Loss may suggest Acoustic Neuroma
- Average difference >10 dB over 1 to 8 KHz range (high Test Sensitivity for Acoustic Neuroma)
- Average difference >15 dB over 0.5 to 3 KHz range (high Test Specificity for Acoustic Neuroma)
- Cheng (2012) Otolaryngol Head Neck Surg 146(3): 438-47 [PubMed]
- Asymmetric Hearing Loss may suggest Acoustic Neuroma
- Other audiology evaluation
- Acoustic Reflex Testing
- Auditory Brainstem Testing (ABR)
- Electronystagmography (ENG)
- Abnormal in 50% of cases, but non-specific
VII. Imaging
-
MRI Brain with contrast and including Internal Auditory Canals
- Best study for identifying Acoustic Neuroma
- Replaces Auditory Brainstem Testing (ABR) for Acoustic Neuroma diagnosis