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 usually 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, which is 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 exactly 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 the 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 affected.
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 symptoms also may be similar to those of other disorders, leading to misdiagnosis. Early detection and prompt treatment, however, can help to reduce the risk of more serious 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 problems in communication 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 take the risks into consideration when deciding on the recommended course of treatment. In cases where the risk outweighs the potential benefits, doctors may recommend monitoring the condition instead of treating it immediately.
Monitoring, rather than treatment, may be recommended in cases that include:
- Patients with no symptoms, especially older patients
- Patients with small or slow-growing tumors
- Patients with prior hearing loss in one ear and a neuroma affecting the other ear
In cases where 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 symptoms of the disease 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 formed.
Current areas of research include:
- Anti-inflammatory therapy. Research has found a connection between the growth rate of acoustic neuromas and the presence of an inflammatory compound called cyclooxygenase 2. It is possible that treatment with aspirin, which inhibits the action of 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, as well.
- 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 therapies that are effective at treating acoustic neuroma, as well as other types of brain tumors.
Acoustic Neuroma Research
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.
Title: Auditory Nerve Test System During Vestibular Schwannoma Resection (ANTS)
Principal investigator: Cameron C. Wick, MD
Washington University School of Medicine
Saint Louis, MO
Many patients diagnosed with vestibular schwannoma (also called acoustic neuroma) eventually lose hearing in the afflicted ear. Improvements in magnetic resonance imaging (MRI) have led to tumors being diagnosed at smaller sizes, however, this has not changed the eventual demise in hearing for most patients. Hearing loss leads to tinnitus, poor sound localization, difficulty hearing in background noise, and imbalance all of which contribute to the decreased quality of life associated with a vestibular schwannoma diagnosis.
Some tumors may be resected while maintaining the integrity of the auditory nerve. When a patient has hearing, the health of the auditory nerve can be monitored during the surgery through auditory-evoked (sound) measurements. When a patient has already lost their hearing or the surgical approach sacrifices all residual hearing, then auditory-evoked measurements can no longer be used and there is no way to monitor the auditory nerve aside from visual inspection.
The Auditory Nerve Test System (ANTS) is a novel device designed to facilitate electrically-evoked auditory nerve monitoring. The ANTS is comprised of three parts: a test electrode, connector cable, and stimulator box. The test electrode functions like a mini-cochlear implant placed within the cochlea during a translabyrinthine surgery. During tumor resection, the test electrode electrically stimulates the auditory nerve allowing surgeons to monitor electrophysiologic data on the health of the auditory nerve. The primary goal of this study is to assess the ANTS during translabyrinthine vestibular schwannoma resections.
If patients are able to maintain an intact auditory nerve following vestibular schwannoma resection then a cochlear implant will be placed during the same surgery. Secondary outcomes measures will investigate cochlear implant outcomes and patient quality of life following this procedure and over the first year of using their cochlear implant. These secondary outcomes will be measured at 3-months, 6-months, and 12-months following cochlear implant activation. The test will assess how well the cochlear implant is working, the cochlear implant’s impact on sound localization and hearing in background noise, and finally various aspects relevant to the patient’s quality of life (tinnitus, balance, hearing, and overall quality of life).
Title: Trial of Selumetinib in Patients With Neurofibromatosis Type II Related Tumors (SEL-TH-1601)
Study Chair: Trent Hummel, MD
Children’s Hospital Medical Center
In this research study, the researchers want to learn more about the effects (both good and bad) the study drug selumetinib has on participants with neurofibromatosis type II (NF2) related tumors.
The researchers are asking patients with NF2 related tumors to be in the study because their hearing has decreased and/or their NF2 related tumor has started to grow.
The goals of this study are:
Determine if selumetinib will stop NF2 related tumors from growing
Measure the changes in hearing after receiving selumetinib for 6 months.
Determine if selumetinib improves how participants feel (physically and emotionally) and how participants can perform daily activities.
Examine tumor tissue, if available, in a laboratory to see if NF2 related tumors have targets of selumetinib
This is a Phase 2 trial to assess the hearing response rate and radiographic response of VS in children and young adults with NF2 who are treated with selumetinib. Dosing will be based on age: For patients with NF2 who are 3 to < 18 years of age, dosing will be based on BSA. Dosing is based on BSA calculated at the beginning of each course. For patients with NF2 who are ≥ 18 to 45 years of age, dosing will be the standard adult dose of 75 mg BID.
Selumetinib is taken orally twice a day continuously. One course is equivalent to 28 days. Therapy may continue for up to two years (26 courses) in the absence of disease progression or unacceptable toxicity.
There will be two treatment strata. Stratum 1 is for those patients who have a target vestibular schwannoma which is causing hearing loss. Stratum 2 will be reserved for patients who exhibit growth of a tumor(s) besides vestibular schwannoma and are therefore not eligible for stratum 1.