- Sporadic Acoustic Neuroma: The majority of cases (90-95%) are sporadic, meaning they occur randomly with no clear genetic link or family history. They are believed to result from a spontaneous mutation in a gene on chromosome 22 that helps produce a tumor-suppressor protein (merlin or schwannomin).
- Neurofibromatosis Type 2 (NF2): This is an inherited genetic disorder that causes tumors to grow on nerve tissue throughout the body. Individuals with NF2 typically develop bilateral acoustic neuromas (tumors on both hearing/balance nerves) and are often diagnosed at a younger age. NF2 is caused by a mutation in the NF2 gene.
- Radiation Exposure: While rare, exposure to radiation, particularly to the head and neck, has been linked to an increased risk.
- Age: Acoustic neuromas are most commonly diagnosed in people between the ages of 30 and 60.
- Hearing Loss:
- Gradual, progressive hearing loss in one ear: This is the most common initial symptom, often affecting high frequencies first.
- Difficulty understanding speech, especially in noisy environments.
- Hearing loss can sometimes be sudden.
- Tinnitus: Ringing, buzzing, roaring, or hissing sound in the affected ear.
- Balance Problems and Dizziness:
- Feeling unsteady, uncoordinated.
- Occasional dizziness or vertigo (sensation of spinning).
- Difficulty walking in a straight line.
- Facial Numbness or Weakness: As the tumor grows, it can press on the trigeminal nerve (causing facial numbness, tingling, or pain) or the facial nerve (leading to facial weakness or paralysis on the affected side).
- Headaches: May occur as the tumor grows larger.
- Ear fullness or pressure.
- Double vision (diplopia) or other eye problems: Less common, usually with very large tumors affecting other cranial nerves.
- Swallowing difficulties (dysphagia) or hoarseness: Rare, with very large tumors.
- Brain Imaging (Crucial):
- MRI (Magnetic Resonance Imaging) with gadolinium contrast: This is the gold standard for diagnosing acoustic neuroma. It provides detailed images of the brain and inner ear, clearly showing the tumor's size, location, and relationship to surrounding structures.
- CT scan (Computed Tomography): Less detailed than MRI but may be used if MRI is contraindicated.
- Auditory Brainstem Response (ABR) Test: Measures how the brain responds to sounds, assessing the function of the hearing nerve. This can help detect problems in the nerve pathway.
- Vestibular Tests: (e.g., Videonystagmography - VNG) To assess balance function and detect abnormalities.
- Observation ("Watch and Wait"):
- For small tumors, slow-growing tumors, or in older patients with minimal symptoms, close monitoring with regular MRI scans is often the initial approach.
- The goal is to avoid unnecessary intervention if the tumor is not causing problems.
- Radiation Therapy (Stereotactic Radiosurgery/Radiotherapy):
- Uses highly focused beams of radiation to target the tumor, aiming to stop its growth or cause it to shrink.
- Examples include Gamma Knife, CyberKnife, and proton beam therapy.
- Often preferred for small to medium-sized tumors or in patients who are not candidates for surgery. It aims to preserve hearing and facial nerve function.
- Surgery (Microsurgical Resection):
- Involves surgically removing the tumor. This is typically done by a neurosurgeon or neuro-otologist.
- The approach chosen depends on tumor size, location, and surgeon preference (e.g., translabyrinthine, retrosigmoid, middle fossa).
- Surgery is often considered for larger tumors that are causing significant symptoms or are growing rapidly.
- Risks include hearing loss, facial weakness, and balance problems.
- Symptomatic Management:
- Hearing aids: For hearing loss.
- Tinnitus management: Sound therapy, counseling (CBT), or masking devices.
- Vestibular rehabilitation therapy (VRT): Exercises to help improve balance and reduce dizziness.