An acoustic neuroma is a rare, noncancerous (benign) brain tumour (growth). The tumour which grows on a nerve in the brain near to the ear can cause problems with hearing and balance, and can cause tinnitus (ringing in the ears). In most cases, the cause is unknown. However, some acoustic neuromas are associated with the disease neurofibromatosis type 2. Acoustic neuromas are slow-growing and are rarely life-threatening. They do not spread to distant parts of the body. Treatment is usually with surgery, but radiotherapy can also be used. A degree of permanent deafness in one ear is usual after treatment for an acoustic neuroma.
What is an acoustic neuroma?
An acoustic neuroma is a rare type of brain tumour (growth). It is a benign (noncancerous) tumour.
The tumour grows along a nerve in the brain (a cranial nerve) that is called the acoustic or vestibulocochlear nerve. This nerve controls your sense of hearing and balance.
Acoustic neuromas grow from a type of cell called a Schwann cell. These cells cover and insulate nerve cells. This is why the tumour is also called a vestibular schwannoma.
Acoustic neuromas tend to grow very slowly and they don't spread to distant parts of the body. Sometimes they are too small to cause any problems or symptoms. Bigger acoustic neuromas can interfere with the function of the vestibulocochlear nerve.
What is the cause of acoustic neuromas?
The cause of most acoustic neuromas is unknown.
About 7 out of every 100 acoustic neuromas are caused by neurofibromatosis type 2 (NF2). NF2 is a very rare genetic disorder that causes benign tumours of the nervous system. It affects about 1 in 350,000 people. Almost everyone with NF2 develops an acoustic neuroma on both acoustic nerves (ie, bilateral tumours). People with NF2 can also get benign tumours on the spinal cord and the coverings of the brain.
How common are acoustic neuromas?
Acoustic neuromas are rare. About 13 people in every million are diagnosed each year with an acoustic neuroma in the UK.
Brain tumours themselves are rare. Brain tumours can be benign (noncancerous) or malignant (cancerous). Brain tumours are divided into two main groups:
- Primary brain tumours originate in the brain. An acoustic neuroma is a primary brain tumour.
- Secondary brain tumours are tumours in the brain that have spread from other parts of the body. They are often referred to a secondaries or brain metastases. These are malignant tumours.
Acoustic neuromas account for about 8 in 100 primary brain tumours. They are more common in middle-aged adults, generally between the ages of 30 and 60 years and extremely rare in children.
Acoustic neuromas seem to be more common in women than men.
What are the symptoms of an acoustic neuroma?
A small acoustic neuroma may cause no symptoms. If you do get symptoms from an acoustic neuroma, these may develop very gradually, as the tumour is so slow-growing.
The symptoms that an acoustic neuroma can cause are very common in the general population. Remember that acoustic neuromas are very rare. You should see your doctor if you have any of these symptoms, but they are more likely to be due to other conditions than a brain tumour.
The most common symptoms of an acoustic neuroma are:
- Hearing loss. Some degree of deafness occurs in 9 in 10 people with an acoustic neuroma. Usually hearing loss is gradual and affects one ear. (Remember old age and earwax are much more common causes of deafness.) The type of deafness caused is called sensorineural deafness and means the nerve for hearing (the acoustic nerve) is damaged. Hearing tests with a tuning fork can help to determine if the deafness is due to a nerve problem, or whether it is more likely due to a blockage in the ear (also known as conductive deafness).
- Tinnitus. This is the medical name for ringing in the ears. About 7 in 10 people with an acoustic neuroma have tinnitus in one ear. The sounds can vary; it does not have to be ringing like a bell. Tinnitus describes any sounds heard within the ear when there is no external sound being made. Tinnitus is a common symptom and not a disease in itself. Other causes of tinnitus include earwax, ear infections, ageing and noise-induced hearing loss.
Other, common symptoms of acoustic neuroma include:
- Vertigo. This is the sensation of the room spinning, often described as dizziness. It is not a fear of heights as some people incorrectly think. This feeling of movement occurs even when you are standing still. Vertigo can be caused by other conditions affecting the inner ear. Nearly half of people with an acoustic neuroma have this symptom, but less than 1 in 10 have it as their first symptom.
- Facial numbness, tingling or pain. These symptoms are due to pressure from the acoustic neuroma on other nerves. The commonly affected nerve is called the trigeminal nerve which controls feeling in the face. About 1 in 4 people with acoustic neuroma has some facial numbness - this is a more common symptom than weakness of the facial muscles. However, it is often an unnoticed symptom. Similar symptoms can occur with other problems, such as trigeminal neuralgia or a tumour growing on the facial nerve (a facial neuroma).
Less common symptoms of acoustic neuroma are:
- Headache. This is a relatively rare symptom of an acoustic neuroma. It can occur if the tumour is big enough to block the flow of cerebrospinal fluid (CSF) in the brain. CSF is the clear, nourishing fluid that flows around the brain and spinal cord, protecting the delicate structures from physical and chemical harm. Obstruction to the flow and drainage of CSF can cause a problem called hydrocephalus (also known as water on the brain). This results in increased pressure and swelling, and the brain effectively becomes squashed within the skull. This can cause headache and, if untreated, brain damage.
- Earache. This is another rare symptom of acoustic neuroma. There are many more common causes of earache.
- Visual problems. Again, this is a rare symptom. If it does happen, it is due to hydrocephalus (see above).
- Tiredness and lack of energy. These are nonspecific symptoms and can be due to many causes. It is possible that a nonmalignant brain tumour could lead to this.
What tests are needed to diagnose an acoustic neuroma?
Acoustic neuromas can be difficult to diagnose. This is partly because they are so rare, and partly because lots of other conditions can cause similar symptoms.
If your GP suspected that you had an acoustic neuroma from your symptoms, you would probably be referred to an ear, nose and throat (ENT) surgeon in a hospital.
You may be referred to an ENT surgeon because of one of your symptoms, and during investigations, an acoustic neuroma might be suspected and found. This is particularly the case if you have recent-onset sensorineural (nerve-related) hearing loss in one ear.
The best test to diagnose an acoustic neuroma is a magnetic resonance imaging (MRI) scan of the brain. An MRI scanner uses a strong magnetic field and radio waves to take a detailed picture of your brain, and of the structures inside it. It is a painless and non-invasive test, but it can be noisy and can make you feel claustrophobic. No X-rays are used (so it is different to a computed tomography (CT) scan that does use X-rays). An MRI scan of the brain can take up to 45 minutes to complete. The pictures are like very thin slices of the brain, and provide detailed information. Some people cannot have an MRI scan. This is usually because of metal implants in the body - such as pacemakers or clips in the brain from brain aneurysm surgery. Contrast is a special dye that is injected into a vein in the arm, during an MRI scan. It helps show up small tumours in the brain on MRI scan. If you have had a previous allergy to the contrast, called gadolinium, or if you have renal (kidney) failure, you may be unsuitable to have an MRI scan with contrast dye. (See separate leaflet called MRI Scan' for more information).
Hearing tests may also be performed if an acoustic neuroma is suspected. This is because one of the most common symptoms of an acoustic neuroma is hearing loss. If an acoustic neuroma is found on a scan, it is useful to know what your hearing in both ears is like before treatment.
What is the treatment for acoustic neuroma?
If you have a very small acoustic neuroma, your doctors might decide that the best approach is to observe and monitor it closely. This is because acoustic neuromas are very slow-growing and may not cause any symptoms for a long time. Remember, acoustic neuromas are not malignant and do not spread, so it is quite safe to watch things for a while. Also, treatments can have complications and side-effects, so the risks and benefits of treatment have to be balanced. If observation is recommended, your condition will be monitored with regular scans.
The main treatments for acoustic neuroma are:
- Stereotactic radiosurgery.
The treatment you are offered will depend on:
- Your suitability for surgery or radiotherapy. Factors such as age and general health govern how fit you are for different treatments.
- Your tumour. The size and position of your acoustic neuroma will influence the type of treatment offered.
The results of the tests and scans you have can also help to determine which type of treatment is best for you and your tumour.
Either a neurosurgeon (brain surgeon) or an ENT surgeon can operate to remove an acoustic neuroma, depending on its size and location on the vestibulocochlear nerve in the brain. The surgery is carried out under a general anaesthetic. Most people with acoustic neuroma are treated with surgery, and about 95 in 100 tumours can be removed completely.
Occasionally (about 5 cases in every 100), a small part of the tumour is left behind. This is usually because it is technically too difficult to remove the whole tumour and/or there is a risk of causing more damage to the nerve or other nearby structures.
If some of the acoustic neuroma is left remaining, it can often be treated with radiotherapy.
After surgery for an acoustic neuroma, you will probably have to remain in hospital for a few days for monitoring. You should be fully recovered within 6-12 weeks, and, if your tumour was completely removed, you should not need any more treatment.
Radiotherapy is a type of treatment generally used for tumours (both benign and malignant). This treatment is given by a clinical oncologist (cancer specialist).
Radiotherapy may completely destroy a tumour, or it may shrink it. It uses high-energy beams of radiation, focused on the tumour. Radiotherapy is commonly used in cancer treatments, especially brain tumours.
Radiotherapy treatment is planned using MRI scans. Your oncologist determines how best to direct the radiotherapy beams on to the tumour, whilst avoiding normal healthy tissue, to minimise damage. You will usually have several sessions of radiotherapy treatment. (See separate leaflet called 'Radiotherapy' for more information.)
Newer types of radiotherapy are increasingly being used for the treatment of brain tumours. One such treatment is called CyberKnife®. Here, radiotherapy is given using a radiotherapy machine on a robotic arm. No frame is needed to hold your head in position, but X-rays are constantly taken during the treatment. This ensures that if there has been the slightest movement, the radiotherapy beams are directed back on target. It is also known as stereotactic radiotherapy.
Stereotactic radiosurgery (SRS)
This is a newer type of treatment that can be used for acoustic neuromas. Stereotactic radiosurgery involves delivering a very precise single dose (usually) of radiation to an extremely well-defined area within the brain - where your acoustic neuroma is.
Stereotactic means locating a point using three-dimensional (3D) co-ordinates. In this instance, the point is the acoustic neuroma tumour within the brain. A metal frame (like a halo) is attached to your scalp and a series of scans are performed to show the exact location of the tumour.
SRS can be given with a normal radiotherapy machine, the CyberKnife® machine or with a technique known as gamma knife treatment. It is used where neurosurgery is thought to be too risky in terms of the chances of complications (such as brain or nerve damage).
SRS is a very specialised type of treatment and is only available in some large hospitals, usually ones with both neurosurgery and oncology centres.
The main advantage of this treatment is to prevent tumour growth and preserve any residual hearing. It tends to shrink rather than remove or destroy the acoustic neuroma. It can be used for very small tumours.
Are any complications likely from an acoustic neuroma?
Complications can be thought of as:
- Due to the tumour itself.
- Due to treatments for acoustic neuroma.
- Recurrence of an acoustic neuroma.
Possible complications due to the acoustic neuroma itself include:
- Hearing loss. The most common symptom of an acoustic neuroma is hearing loss. This is due to damage to the vestibulocochlear nerve that the acoustic neuroma is growing on. Even if the acoustic neuroma is removed with surgery, or destroyed with radiotherapy, a degree of permanent hearing loss in one ear is usual. The extent to which you will be affected by hearing loss varies from person to person. It can depend on things such as how big the tumour is, how much damage has been caused and how difficult treatment was. It is possible to be rendered profoundly or completely deaf on the side of the acoustic neuroma, but most people will have normal functioning (and thus hearing), in their unaffected ear.
- Hydrocephalus. If your acoustic neuroma grows very large, a complication called hydrocephalus (water on the brain) can occur. This happens because the flow of cerebrospinal fluid (CSF) is obstructed (see above, under 'Less common symptoms of acoustic neuroma'). Pressure can build up inside the brain, leading to permanent brain damage if not identified and treated. The condition can be treated by inserting a drainage tube (called a shunt) to relieve the pressure and allow the CSF to flow. Hydrocephalus is very unlikely if you have treatment for an acoustic neuroma.
- Damage caused by pressure on other nerves in the brain, or on the brainstem. If the acoustic neuroma is growing and untreated, it can cause problems by pressing on nearby structures in the brain. This can lead to some of the symptoms of acoustic neuroma, listed earlier. Long-term pressure can cause irreversible damage and permanent problems. It is possible that the trigeminal nerve (which controls feeling in the face) or the facial nerve (which controls movements of the muscles of the face) can be affected. The brainstem is the lower part of your brain that connects to the spinal cord. It controls vital bodily functions. If the brainstem is affected (very rare) then it is possible to have problems with breathing, consciousness, the circulation, co-ordination and balance and with the function of your arms and legs. Again, if you have treatment for your acoustic neuroma before it has had the chance to grow very big (remember, it is a slow-growing tumour), this sort of complication is very unlikely.
Possible complications due to treatments for acoustic neuroma include:
- Damage to the facial nerve, causing a facial nerve palsy. The facial nerve is the nerve in the brain that controls movements in the muscles of the face. If an acoustic neuroma has grown quite large, removal during surgery can potentially lead to damage of this neighbouring nerve. If the nerve is damaged, there will be paralysis of part of the face. This can cause a problem with drooping of one side of the face. In some cases, physiotherapy will help but, in others, the damage is permanent. Obviously, during surgery, great care is taken to identify and avoid damage to surrounding nerves.
- Damage to the vestibulocochlear nerve, leading to deafness. As mentioned, a degree of hearing loss is normal after treatment for acoustic neuroma. If you have NF2 and bilateral tumours, there is a strong chance that after surgery, you will completely lose the hearing in both of your ears.
- Damage to the trigeminal nerve, leading to facial numbness (loss of feeling). In the same way that the facial nerve can be damaged during surgery to remove an acoustic neuroma, the trigeminal nerve can also be injured. If this occurs, there is loss of sensation to parts of the face.
Recurrence of acoustic neuroma
Fewer than 5 in every 100 acoustic neuromas recur (come back). So it is uncommon, but possible. It is more likely if you have NF2. It could cause any of the symptoms mentioned earlier, or any of the complications.
After treatment for acoustic neuroma you will generally be followed up in an outpatient clinic to check for any symptoms or signs of a recurrence.
Driving and acoustic neuroma
If you hold a Group 1 entitlement driving licence (car or motorbike) then you do not need to notify the DVLA of your condition, unless you experience sudden and disabling giddiness.
If you hold a Group 2 entitlement driving licence (lorries and buses), you also do not need to inform the DVLA of your condition, unless you experience disabling giddiness or the condition is bilateral (affects the left and right acoustic nerve).
What is the outlook (prognosis) with an acoustic neuroma?
The outlook is generally very good, particularly as it is a benign tumour. It is generally very suitable for treatment and complications are uncommon. A degree of hearing loss in one ear after treatment, should, however, be expected.
Further support and information
British Acoustic Neuroma Association
A site designed and developed by people affected by acoustic neuroma. There are public areas to the website and an opportunity to become a member of the association.
Action on Hearing Loss
Formerly the RNID, they are a charitable organisation working on behalf of the UK's 9 million deaf and hard of hearing people. The website offers support, information and even an online shop for products to assist people with impaired hearing.
The Neurofibromatosis Association
A UK-based organisation offering support and information for people affected by the diseases neurofibromatosis 1 and 2.
Further reading & references
- Acoustic Neuroma, British Association of Otorhinolaryngologists Head and Neck Surgeons (2001)
- Kutz JW et al; Skull Base, Acoustic Neuroma (Vestibular Schwannoma), eMedicine, Sep 2009
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Tim Kenny
Dr Katrina Ford
Dr Tim Kenny