Many people with acoustic neuromas want their tumor to disappear and for their hearing and balance to return. These are reasonable expectations, but current technology cannot fully achieve these goals.
Small acoustic neuromas that cause minor or no symptoms can be carefully monitored with regular MRI scans. If the acoustic neuroma grows, surgery or radiation treatment may be needed.
Symptoms
The most common symptom of acoustic neuroma is gradual hearing loss, sometimes accompanied by ringing in the ears (tinnitus) and a feeling of fullness in the ear. Other symptoms may include clumsiness and difficulty finding where sounds are coming from.
Depending on the size of the tumor, symptoms vary. Small acoustic neuromas that are not causing significant symptoms do not require treatment and can be monitored with serial imaging and audiologic evaluation. Larger acoustic neuromas that are compressing the brain stem or other important structures may require surgery and/or radiation therapy.
When a tumor grows, it can press on the nerve fibers that connect the inner ear to the brain. These nerves are responsible for hearing and balance. A growing acoustic neuroma can also press on the facial nerve, which controls muscles that move the face and feel sensations such as touch. The pressure of a growing acoustic neuroma on the brain stem can cause a buildup of fluid at the base of the skull, a condition known as hydrocephalus.
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If the acoustic neuroma is in the upper part of the skull, it can also compress the vagus nerve and glossopharyngeal nerve, which control the voice and swallowing. Depending on the size of the tumor, acoustic neuromas can also lead to unsteady gait, difficulty speaking and/or swallowing, headache and/or neck pain.
The eighth cranial nerve, which gives rise to acoustic neuromas, is closely related to CN 7 (the facial nerve), resulting in weakness and numbness on the same side of the face. This nerve is also connected to CN 5 (the trigeminal nerve), leading to pain that mimics typical trigeminal neuralgia. It can also influence CN 24 and CN 30, which control tear production and taste perception, respectively.
The diagnosis of an acoustic neuroma is made through a detailed history and a physical examination, followed by an MRI or CT scan. MRI is the preferred diagnostic test for these brain tumors because it can detect even the smallest acoustic neuromas. A CT scan can be used in place of an MRI, but it is not as sensitive and does not provide as much detail about the location and size of the tumor.
Diagnosis
The first symptoms of acoustic neuroma are often subtle, and it may be months or even years before they are noticed. They can include a gradual loss of hearing in one ear (hearing loss), ringing in the ears (tinnitus) or a feeling that there is fullness in the ear. Some patients have balance problems or experience unsteady movements or confusion. If these symptoms are severe, it is important to see a doctor.
A doctor will perform a complete examination, including an ear test and imaging scans. MRI scans (magnetic resonance imaging) can show the presence of an acoustic neuroma and can pinpoint its location within the skull. They can also help determine how fast the tumor is growing, which will influence whether or not it needs to be treated.
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An acoustic neuroma is a rare noncancer tumor that grows from an overproduction of Schwann cells, which normally wrap around and support nerve fibers. It grows in the inner ear, where it presses on hearing and balance nerves, as well as nerves that control facial muscles and sensation. When large, it can also press on blood vessels and brain structures.
Your doctor will take a careful history and ask you about your symptoms. They will also check your general health and family history. An acoustic neuroma can be caused by a gene change, but in many cases, the cause is not known. If you have the rare disorder neurofibromatosis type 2, it can increase your risk of developing an acoustic neuroma.
The decision to treat an acoustic neuroma will be made by your doctor after considering its size, how fast it is growing and the severity of your symptoms. If the tumor is small and not causing symptoms, it may not need to be removed. Ongoing MRI scans are recommended to monitor the growth of the tumor. If the tumor is causing symptoms, surgery may be recommended. Treatment options also include radiation therapy. This is an option for older patients, or those with very small tumors that are not causing symptoms. In these cases, the radiation dose is lower and there is a greater likelihood of maintaining normal function after treatment.
Treatment
Symptoms of acoustic neuroma are usually quite subtle, especially in the early stages. People may mistake them for common problems of aging, such as hearing loss, ringing in the ear (tinnitus) and feeling unsteady. It is important to seek medical attention if you notice these symptoms. Early diagnosis and treatment can prevent the tumour from growing to a point where it causes serious side effects such as complete hearing loss or brain compression.
Treatment for acoustic neuroma depends on a number of factors, such as the size and location of the tumour and its rate of growth. Very small tumors, particularly those confined to the inner ear canal, often do not grow at all and are considered safe to monitor with ongoing MRI scans. This is called active monitoring and involves shared decision making between you, your doctor and the care team.
For small and nongrowing acoustic neuromas, radiotherapy is an option. This uses high-energy rays to destroy tumour cells. It is used to stop a tumour from growing and, in some cases, can also shrink it. At Yale Medicine, we use a technique called stereotactic radiosurgery (SRT). It allows us to accurately target the tumour with radiation while minimising the impact on surrounding healthy tissue.
Surgical removal of an acoustic neuroma is sometimes necessary, but it is not always possible or appropriate, particularly in children or young adults. This is because the tumour can recur and the risk of long-term problems with facial nerve function or brain damage is increased with surgery.
Surgery can be performed under general anesthesia. A section of the skull is removed to allow access to the area where the tumour is located in the brain. The surgeon removes the tumour, but leaves a small part behind in order to avoid damaging nerves that affect your face. You may then need radiotherapy after surgery to prevent the tumour from recurring.
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For large acoustic neuromas that are causing symptoms, or are growing rapidly, surgery is an option. This is particularly the case for people with a genetic condition called neurofibromatosis type 2, who are more likely to develop these types of tumor.
Recovery
If the tumor does not cause symptoms that interfere with daily life, doctors may choose to monitor it. This involves reassurance and follow-up MRI exams. At Mayo Clinic, we offer Gamma Knife radiosurgery, which is a noninvasive way to shrink or eliminate an acoustic neuroma. Unlike surgical removal, this approach does not leave behind any tissue that can grow back.
In children and teens, acoustic neuromas can cause unsteady movement (ataxia), clumsiness and mental confusion. They most often occur in one ear, but can also affect the balance nerve on both sides of the head. These tumors can be caused by a change in a gene on chromosome 22, which is part of the genetic disorder known as neurofibromatosis type 2.
If an acoustic neuroma becomes too large, it can put pressure on the brain stem, leading to loss of balance and hearing, facial numbness or weakness and a buildup of cerebrospinal fluid in the skull. These are all serious side effects and should be evaluated immediately by a health care professional.
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Doctors recommend surgery if a patient experiences any of these problems or when a tumor is growing rapidly. In addition to determining the size of the tumor, doctors consider the person’s age and overall health, how serious the symptoms are and what the acoustic neuroma is pressing against in the skull.
After surgery, the doctor will ask you to follow certain restrictions on activity or at home exercises to ease discomfort and strengthen your facial muscles. They will also perform a hearing test to determine whether the acoustic neuroma has affected your hearing. For patients who still experience hearing loss or ringing in the ears (tinnitus) after surgery, a speech-language therapist can teach you strategies to compensate for these side effects.
Those who have had a acoustic neuroma removed will continue to see their doctor for regular follow-up visits. The otolaryngologist will examine the ears and take an MRI of the skull to check the location, size and progression of the tumor. In addition, the Mayo Clinic’s MRI and radiation therapy team will monitor your progress and work with your doctor to make treatment decisions.
