Causes
The exact cause of most acoustic neuromas is unknown. However, about 5-10% of cases are associated with a genetic disorder called Neurofibromatosis Type 2 (NF2).- 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.
Symptoms
Symptoms of an acoustic neuroma typically develop slowly over months or years as the tumor gradually grows and presses on the vestibulocochlear nerve and surrounding brain structures. The earliest symptoms are often related to hearing and balance.- 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.
Diagnosis
Diagnosing an acoustic neuroma requires a comprehensive evaluation, as early symptoms can be subtle or mistaken for other conditions.Medical History and Physical Exam
The doctor will ask about your symptoms, medical history, and perform a neurological exam, checking hearing, balance, and facial sensation/movement. Hearing Test (Audiometry): This is typically the first test. It can confirm hearing loss and its pattern (often asymmetrical, affecting one ear more than the other), which is a key indicator.- 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.
Treatment
Treatment for acoustic neuroma depends on the tumor's size, growth rate, the patient's age, overall health, and symptoms. Since they are benign, the goal is to control growth, preserve nerve function, and manage symptoms.- 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.
Living With an Acoustic Neuroma
Most acoustic neuromas grow slowly or not at all, and many people live with one for years under observation. The practical questions are how monitoring works, what treatment does to hearing and balance, and how to manage a single-sided hearing loss well.
What watch-and-wait actually involves
Observation means an MRI about six months after diagnosis, then yearly if the tumor is stable, with a hearing test at each visit. Roughly half of small tumors show no meaningful growth over several years. Treatment is recommended when growth is documented, when the tumor is already large, or when symptoms progress, rather than on a timetable. Hearing that is still useful at diagnosis is more likely to be preserved when a growing tumor is treated while it is small, which is the argument against waiting too long once growth is seen.
Radiosurgery and surgery: what to expect
Stereotactic radiosurgery is a single outpatient session; the tumor may swell briefly on MRI in the first year before stabilizing, and hearing tends to decline gradually over years in the treated ear. Surgery removes the tumor in one operation with several days in hospital and weeks of recovery; balance is worst in the first weeks and improves as the brain compensates, and facial weakness, when it occurs, usually recovers over months. Neither treatment reliably restores hearing already lost.
Hearing on one side
Single-sided deafness makes it hard to locate sounds and to follow conversation in noise. A CROS hearing aid routes sound from the deaf side to the hearing ear, and a bone-conduction implant does the same through the skull; a cochlear implant is an option in selected cases. Protecting the good ear from noise matters more than ever, and the hearing loss page explains the devices. Untreated hearing loss is linked with cognitive decline, which our hearing loss and dementia article covers. Tinnitus in the affected ear often persists after treatment; our tinnitus article covers what helps.
Balance, eyes, and the face
Vestibular rehabilitation, a program of head and eye exercises, speeds the brain's adjustment after surgery or as the nerve fails, and walking daily on uneven ground does more than resting. If the facial nerve is weakened, the eye on that side may not close fully, and lubricating drops by day, ointment at night, and taping the lid closed in sleep prevent corneal damage; the dry eye page covers protection. Sudden facial weakness without a known tumor is far more often Bell's palsy.
What it is confused with
One-sided hearing loss with fluctuating fullness and vertigo attacks suggests Meniere's disease, and the MRI that separates the two is why it is ordered. Hearing that drops suddenly in one ear is sudden sensorineural hearing loss, treated within days with steroids, and a tumor is found in a small share of those cases. Tumors on both sides, or a diagnosis under 30, prompt testing for neurofibromatosis type 2. Our ear, nose, and throat team coordinates monitoring and the specialist team. The NIDCD and the NINDS publish patient guidance on vestibular schwannoma.
If you have hearing loss or ringing in one ear that has never been imaged, or a known neuroma that is overdue for its MRI, schedule a visit.