What is Acoustic Neuroma?
An acoustic neuroma is a non-cancerous tumor that grows on the nerve that connects the brain to the inner ear. It is also sometimes called a vestibular schwannoma because it affects the Schwann cells (cells that surround nerves) on the vestibular nerve, the nerve responsible for our senses of hearing and balance.
Acoustic neuromas are almost always slow-growing tumors, and they often remain very small. In most cases, symptoms arising from the tumor affect only hearing and balance. In rare cases, the tumor may grow large enough to put pressure on other nerves or the brain stem, resulting in more severe (and possibly life-threatening) symptoms.
Symptoms of Acoustic Neuroma
If an acoustic neuroma remains very small, it may produce no symptoms at all. Initial symptoms in most cases impact hearing and balance. Common symptoms include:
- Loss of hearing, usually in one ear. This is the first symptom in about 90% of cases. Hearing loss is typically gradual, but sometimes it may be sudden.
- Ringing in the affected ear (tinnitus)
- Feeling of fullness in the affected ear
- Problems with balance
Less common symptoms occur when the neuroma is large enough to put pressure on other nerves. These symptoms can include:
- Numbness or tingling in the face
- Weakness or paralysis in facial muscles
- Difficulty swallowing
What Causes Acoustic Neuroma?
An acoustic neuroma affects the cells that surround nerves outside the central nervous system. Normally, these cells, called Schwann cells, produce a sheath that protects the nerve cells. In the case of an acoustic neuroma, the Schwann cells surrounding the eighth cranial nerve, responsible for transmitting signals to the brain related to hearing and balance, grow abnormally. As the cells grow, they form a tumor that puts pressure on the nerve, impairing its function and causing symptoms.
Scientists don’t know precisely what causes the Schwann cells to begin growing abnormally. Studies have tried to identify risk factors that may make an individual more likely to develop an acoustic neuroma. Possible risk factors include:
- Radiation exposure to the head and neck, including from treatment of certain cancers
- Prolonged exposure to loud noises, such as a noisy work environment
- Certain genetic factors
Is Acoustic Neuroma Hereditary?
In almost all cases, acoustic neuromas appear to develop spontaneously, without any connection to inherited risk factors. Scientists believe that tumors occur when a particular gene malfunctions, causing an increased risk for tumor development. Most of the time, the faulty gene is not inherited. Instead, it stops working correctly because of an unknown trigger.
In about 5% of acoustic neuroma cases, the faulty gene is passed from parent to child. In these cases, the gene malfunction causes a rare disorder called neurofibromatosis type 2 (NF2). People with this disorder often develop tumors of the brain and spinal cord. They are also more likely to develop acoustic neuromas that affect both ears, in contrast to non-inherited cases where only one ear is usually involved.
NF2 follows an autosomal dominant inheritance pattern, meaning that a child can develop the disorder if they inherit the faulty gene from only one parent.
How Is Acoustic Neuroma Detected?
Acoustic neuroma can be hard to detect in its initial stages because its symptoms are often relatively minor and may go unnoticed. Early signs also may be similar to those of other disorders, leading to misdiagnosis. However, early detection and prompt treatment can help reduce the risk of more severe complications in the future.
Early signs of acoustic neuroma include:
- Gradual hearing loss in only one ear
- Ringing in only one ear
- Feeling of fullness in only one ear
How Is Acoustic Neuroma Diagnosed?
To confirm or rule out an acoustic neuroma diagnosis, a doctor will first conduct a physical exam and take a medical history. If the results of these steps suggest that a neuroma may be present, further diagnostic steps can be used:
- Hearing test. An exam conducted by an audiologist can detect if any hearing loss is confined to one ear, an indication that a neuroma could be the cause.
- Electronystagmography. This test looks for problems in balance by measuring small, involuntary eye movements. The results of this test can also suggest that a neuroma could be involved.
- Brainstem auditory evoked response (BAER). This test measures the brain’s response to sound, and it may be able to detect communication problems between the brain and the cranial nerve.
- Imaging. Magnetic resonance imaging (MRI) or computed tomography (CT) may be used to identify the size and location of a neuroma.
PLEASE CONSULT A PHYSICIAN FOR MORE INFORMATION.
How Is Acoustic Neuroma Treated?
In some cases, treatment for acoustic neuroma is not recommended. Surgical interventions to remove the tumor sometimes cause complications or worsen symptoms, so doctors consider the risks when deciding on the recommended treatment course. In cases where the risk outweighs the potential benefits, doctors may recommend monitoring the condition instead of treating it immediately.
Cases in which observation rather than treatment may be recommended include:
l Patients with no symptoms, especially older patients
l Patients with small or slow-growing tumors
l Patients with prior hearing loss in one ear and a neuroma affecting the other ear
If the neuroma is fast-growing or is causing severe symptoms, surgery to remove the tumor may be recommended. The goal of the surgery varies depending on the size and location of the tumor. Sometimes the entire tumor is removed, and sometimes only part of the tumor is removed.
Potential long-term complications of surgery include:
- Worsening of symptoms, including hearing loss or balance problems
- Numbness or tingling in the facial muscles
- Weakness of the facial muscles
- Leakage or infection of cerebrospinal fluid
- Stroke or bleeding in the brain
Radiation therapy or radiosurgery may be used to stop or slow the growth of the tumor. Commonly used radiation-based interventions include stereotactic radiosurgery, stereotactic radiotherapy, and proton beam therapy.
How Does Acoustic Neuroma Progress?
A fast-growing acoustic neuroma may eventually put pressure on other nerves or the brain stem. These cases are rare, but they can result in symptoms that are generally more widespread and/or severe than those typical of a smaller neuroma.
Potential complications include:
- Weakness or paralysis of facial muscles
- Chronic numbness or tingling in facial muscles
- Difficulties with swallowing
- Persistent headaches
- Accumulation of fluid in the brain, which may cause uncontrollable muscle movements, confusion, and headaches. In very rare cases, these complications can be life-threatening.
How Is Acoustic Neuroma Prevented?
Because the causes of acoustic neuroma are not known, there is not yet any known way to prevent the tumor from occurring. People with a family history of neurofibromatosis type 2 may want to consult a genetic counselor to assess their risk of passing the disease’s associated gene variation to their children.
Acoustic Neuroma Caregiver Tips
Keep these tips in mind as you care for your loved one:
- Educate yourself about the disorder. Learn all you can about acoustic neuroma. The disease symptoms are invisible, and sometimes your loved one might feel as if no one understands what they’re going through. Aim to make yourself an expert on the condition so that you can be a better caregiver and a better advocate for your loved one’s treatment.
- Be compassionate. Your loved one is likely to be frightened if their hearing is threatened or if their symptoms limit their daily routines. Show them that you understand their concerns and that you’re ready to support them.
- Get help. Finding people who know what it’s like to deal with acoustic neuroma can make it easier for you and your loved one to cope with the disease. Ask your healthcare provider for a referral to support groups and resources.
Acoustic Neuroma Brain Science
Scientists are working to better understand acoustic neuroma, both in terms of its causes and the chemical processes that make tumors grow. Research is focused on finding ways to stop the tumors from forming in the first place or to slow their growth once they have developed.
Current areas of research include:
- Anti-inflammatory therapy. Research has found a connection between acoustic neuromas’ growth rate and the presence of an inflammatory compound called cyclooxygenase 2. It is possible that treatment with aspirin, which inhibits cyclooxygenase 2, may slow the growth of these tumors.
- Neurofibromatosis type 2 (NF2) treatments. The development of drugs to treat the growth of tumors in patients with NF2 could lead to treatments for spontaneously occurring acoustic neuromas.
- Genetic research. Scientists are working to understand how the gene associated with acoustic neuroma encourages the growth of tumors. The study of this genetic mechanism could lead to effective therapies for treating acoustic neuroma and other types of brain tumors.
Acoustic Neuroma Research
Title: Study of Aspirin in Patients With Vestibular Schwannoma
Principal Investigator: Scott Plotkin, MD, PhD
Massachusetts General Hospital
This is a phase II prospective, randomized, double-blind, longitudinal study evaluating whether the administration of aspirin can delay or slow tumor growth and maintain or improve hearing in VS patients.
Title: Cochlear Implant Following VS Removal or Labyrinthectomy
Principal Investigator: Oliver Adunka, MD
Ohio State University
This study is a prospective, clinical study to determine if it is safe and effective to use a cochlear implant over time in individuals undergoing removal of a vestibular schwannoma (VS), benign tumor of the hearing and balance nerve or undergoing a labyrinthectomy for treatment of Meniere’s disease. Individuals undergoing these surgeries will be deaf on the surgical side after the procedure. Currently, cochlear implants are approved for use and not considered investigational in individuals with hearing loss on both sides. However, the use of a cochlear implant for these patient populations (single-sided hearing loss) will be considered a new use of an approved device. Participants undergoing surgery to remove a VS or having a labyrinthectomy will have a cochlear implant inserted after the surgical procedure for clinical care. Approximately 4 weeks after surgery, participants will be fitted with an external speech processor on the surgical side that will stimulate the internal cochlear implant.
Title: Hearing Outcomes Using Fractionated Proton Radiation Therapy for Vestibular Schwannoma
Contact: Helen A. Shih, MD
Massachusetts General Hospital
In this research study, we are looking at another type of radiation called proton radiation which is known to spare surrounding normal tissues from radiation. The proton radiation will be delivered using fractionated stereotactic radiotherapy (FSRT) to improve the localization of the small tumor target. Proton radiation delivers minimal radiation beyond the area of the tumor. This may reduce side effects that patients would normally experience with conventional radiation therapy. In this research study, we are looking to determine the effects of fractionated proton radiotherapy on long-term hearing preservation and controlling tumor growth.