An acoustic neuroma, which is also known as a vestibular Schwannoma, is a benign (non-cancerous) brain tumour (growth).

An acoustic neuroma grows on the acoustic nerve (vestibulocochlear nerve), which helps control hearing and balance. The acoustic nerve runs alongside the facial nerve, which carries information from the brain to the muscles of the face.

Therefore, acoustic neuromas can cause problems with:

• hearing – causing hearing loss or tinnitus (the perception of noise inside the ear or ears that comes from inside the body rather than from an outside source)
• balance – causing vertigo (the sensation of movement even when completely still)
• the facial muscles – causing numbness

The symptoms of an acoustic neuroma can vary in severity, and they tend to develop gradually (see Acoustic neuroma - symptoms).

How common is an acoustic neuroma?

All types of brain tumour are relatively rare. Every year, approximately 20 people out of every million in the population are diagnosed with an acoustic neuroma.

Acoustic neuromas tend to be more common in women than in men, although the reasons for this are not yet understood. People between 40 and 60 years old are most commonly affected. The condition is very rare in children.

Outlook

An acoustic neuroma tends to grow very slowly, and will not spread from the original site of the tumour. Sometimes, an acoustic neuroma is so small and grows so slowly that it does not cause any symptoms or problems.

An acoustic neuroma is not usually a life-threatening condition, but the symptoms can disrupt day-to-day life. For example, a loss of hearing may affect a person’s ability to communicate with other people.

In very rare cases, the tumour can grow large enough to press on the brain (see Acoustic neuroma - complications). However, most acoustic neuromas can be treated before they get to this stage using:

• surgery to remove the tumour
• radiotherapy (waves of radiation) to destroy the tumour

In many cases of acoustic neuroma, some degree of hearing loss may be permanent.  

A small acoustic neuroma may not cause any symptoms. As acoustic neuromas tend to grow slowly, your symptoms may develop gradually.

The growth rate for acoustic neuromas is around 1-2mm every year. However, they may not grow constantly, and there could be long periods when the tumour does not grow at all.  

Symptoms of an acoustic neuroma include:

• hearing loss – this is the most common symptom and usually develops gradually in one ear, though in some cases it can develop suddenly or affect both ears
• tinnitus, which is the perception of noise in one ear or both ears that comes from inside the body rather than from an outside source – for example, you may hear ringing in your ears
• vertigo – the sensation that you or the environment around you is moving or spinning; you may feel the sensation of movement even when you are standing completely still
• facial numbness, tingling or pain, which can occur if the tumour (growth) begins to press on the nerve that controls feeling and sensation in you face (the trigeminal nerve). However, this is a rare symptom and could suggest another condition, such as a facial neuroma (a tumour growing on your facial nerve)
• headaches – this is a relatively rare symptom, although it can happen if the tumour blocks the flow of cerebrospinal fluid (CSF – the fluid that surrounds your brain and protects it from trauma)
• temporary sight problems – this is rare and is also caused by a CSF blockage
• earache – this is another rare symptom

Hearing loss and tinnitus are the most common symptoms of acoustic neuroma and they usually only affect one ear. However, if you have acoustic neuroma caused by neurofibromatosis type 2 (a rare inherited condition, see Acoustic neuroma - causes), your symptoms may affect both ears. 

Hearing loss is not necessarily worse for larger tumours. In some cases, particularly if your acoustic neuroma is caused by neurofibromatosis type 2, hearing loss may be worse on the side with the smaller tumour. 

Progressive symptoms

If your acoustic neuroma is growing, the symptoms listed above may get worse as the tumour increases the pressure on your:

• vestibulocochlear nerve – also known as the acoustic nerve, it helps to control hearing and balance
• trigeminal nerve, which controls the feeling in your face.

If your acoustic neuroma presses on your brain stem (the lower part of your brain that attaches to your spinal cord) you may also experience:

• numbness in other parts of your body
• ataxia – a loss of physical co-ordination that affects your ability to do activities such as swallowing, speaking, walking or writing

Brain stem

The brain stem is the lower part of the brain that is connected to the spinal cord and is responsible for regulating most of the automatic functions of the body that are essential for life, such as breathing.

Spinal cord

The spinal cord is a column of nervous tissue located in the spinal column. It sends messages between the brain and the rest of the body.

Acoustic neuromas grow from a type of cell called a Schwann cell. Schwann cells cover nerve cells, helping to keep them insulated. Acoustic neuromas are therefore sometimes called vestibular Schwannomas.

The cause of most acoustic neuromas is unknown. There are no risk factors for developing an acoustic neuroma.

It is thought that a fault in a gene (unit of genetic material) that helps stop tumours growing may be responsible, although researchers have not yet identified the gene that is affected.

It is also not known what causes some acoustic neuromas to start or continue growing while others remain the same size. 

Neurofibromatosis type 2

Around 5 out of 100 cases of acoustic neuroma are caused by a rare, inherited condition called neurofibromatosis type 2.

Neurofibromatosis causes soft, benign (non-cancerous) tumours to grow on the nerve tissue in the body. Neurofibromatosis type 2 can cause tumours to grow on the acoustic nerve and sometimes on the skin. It can also cause other conditions, such as cataracts (cloudy patches that grow over the lens of the eye).

Neurofibromatosis type 2 usually affects both acoustic nerves. This means that the hearing in both of your ears is more likely to be affected.

See the Health A-Z topic about Neurofibromatosis for more information about this condition.

An acoustic neuroma can be difficult to diagnose. This is because the symptoms often develop gradually and can therefore be difficult to spot. Symptoms such as dizziness and hearing loss can also be attributed to a number of other conditions, such as Ménière's disease (a rare disorder that affects the inner ear).

If your GP suspects that you may have an acoustic neuroma, you will be referred to a hospital or clinic for further testing.

Neurological testing

You may need to have a series of tests to check whether your nervous system (brain, nerves and spinal cord) is being affected by an acoustic neuroma.

Hearing tests

Part of the neurological testing process involves checking your hearing because an acoustic neuroma often affects your hearing. Hearing tests that you may have include:

• auditory brainstem response (ABR) test – which is usually carried out in an audiology clinic (a hospital department that investigates hearing problems); sounds are played through earphones and a computer records your responses
• pure tone audiometry test – a machine called an audiometer is used to produce sounds at various volumes and frequencies while you listen through headphones and press a button when you hear a sound
• speech recognition audiometry test – tests your ability to recognise words that are spoken at different volumes

Magnetic resonance imaging (MRI) scan

A magnetic resonance imaging (MRI) scan is one of the most accurate ways of diagnosing an acoustic neuroma. This type of scan allows your doctor to see the size and position of your tumour (growth).

An MRI scan uses a strong magnetic field and radio waves to take a detailed picture of the inside of your head. It is a painless procedure that takes 15 to 60 minutes to complete. However, it can be noisy and you may feel slightly claustrophobic.

See the Health A-Z topic about MRI scans for more information about this procedure.

MRI scans do not use X-rays (a type of high frequency radiation). However, if you are pregnant and in your first trimester (up to week 13 of the pregnancy) your MRI scan is likely to be delayed. After the first trimester, MRI scans can be used safely.

There are several different treatment options for an acoustic neuroma. Which treatment you have will depend on a number of factors, including:

• your age
• your overall health
• the size and position of your tumour

The results of any tests or scans you have had will also help to determine the best course of treatment. Your acoustic neuroma will usually be treated by a team of specialists and other health professionals including:

• a neurosurgeon – a surgeon who specialises in operating on the nervous system (brain, spinal cord and nerves)
• an ear, nose and throat (ENT) surgeon – a surgeon who specialises in operating on conditions that affect the ears, nose or throat
• a neurologist – a doctor who specialises in diagnosing and treating conditions that affect the brain and nervous system; for example, by deciding which tests are necessary and prescribing medication 
• an oncologist – a doctor who specialises in cancer and tumours; for example, using radiotherapy (controlled doses of high-energy radiation) to treat benign (non-cancerous) tumours, such as acoustic neuromas

Monitoring

If your acoustic neuroma is very small or growing very slowly, you may be advised not to have any immediate treatment. Instead, your condition will be monitored. Some research has suggested that as many as three-quarters of acoustic neuromas do not appear to be growing, so monitoring the tumour (growth) is all that is needed.

Although simply monitoring your acoustic neuroma may seem like nothing is being done about your condition, it can be the best option because the risks associated with surgery or radiotherapy (see below) outweigh the risk of an acoustic neuroma affecting your health.

To help monitor your condition you will need to have regular magnetic resonance imaging (MRI) scans (where a magnetic field and radio waves are used to create an image of the inside of your body). The MRI scan will check the size and growth of your acoustic neuroma. Other treatments may be considered if the tumour:

• shows any signs of growing
• significantly affects your health

See the Health A-Z topic about MRI scans for more information about this procedure. You may need to have an MRI scan every one or two years, although this will depend on your general health and the severity of your tumour.

Microsurgery

Acoustic neuromas can be treated using microsurgery to remove the tumour. The surgery is carried out under general anaesthetic (a painkilling medication that makes you unconscious), and the acoustic neuroma is removed through an incision (cut) that is made in your skull.

In most cases, the acoustic neuroma can be completely removed, although in rare cases a small part of the tumour may be left behind. This may be necessary to minimise the risk of causing nerve damage. In cases where a small part of the tumour remains, it can usually be effectively treated using radiotherapy (see below).

Hearing loss

After acoustic neuroma surgery, many people find that their hearing is permanently affected to some degree. Usually, your neurosurgeon works alongside a hearing surgeon during your operation to minimise the risk of your hearing being affected.

In most cases, the larger your acoustic neuroma the greater the risk that your hearing will be affected. If your tumour is more than 1.5cm (0.6 inches) in diameter, you will almost certainly have permanent hearing loss after the surgery.

If your hearing is affected, it will usually only be affected in one ear. If this is the case, after surgery, you may be able to be fitted with a hearing aid which will help to divert sound from your affected ear to your good ear.

If your acoustic neuroma is caused by neurofibromatosis type 2, and the tumour has grown on both sides of your acoustic nerve, there is a strong likelihood that, after surgery, you will completely lose the hearing in both of your ears. For this reason, surgery for a tumour on both sides of the acoustic nerve will usually be delayed for as long as possible. Surgery will only be performed if the acoustic neuroma significantly affects the rest of your health.

See the Health A-Z topic about Hearing impairment - treatment for more information about treating hearing loss.

Facial nerve

Occasionally, surgery can damage the facial nerve. This is because the acoustic nerve is very close to the facial nerve. Your surgeon will try very hard not to damage your facial nerve, but sometimes damage is unavoidable, particularly in cases where the acoustic neuroma is large.

If your facial nerve is damaged during surgery you may find that:

• your speech is no longer as clear
• you have problems swallowing (dysphagia)
• you have a droop on one side of your face (facial palsy)

These symptoms may improve with physiotherapy (where physical methods, such as massage and manipulation, are used to promote healing and wellbeing). However, it is important to be aware that some damage to your facial nerve may be permanent.

Damage to your facial nerve can also affect your eyes - for example you may have difficulty blinking or completely closing your eye on the side that was operated on. This may lead to your eyes drying out.

For people with tumours that are smaller than 1.5cm (0.6 inches) across, less than 1 person in every 10 will have their facial nerve badly affected after treatment.

For people with tumours of more than 2.5cm (1 inch) across, around 2 in 10 people will have facial nerve weakness after surgery. Facial nerve weakness is likely to be temporary, but it may take several months to recover. About two-thirds of people with tumours that are 4-5cm (1.6-2 inches) across have the function of their facial nerve fully restored following surgery.

Recovery from surgery

Following surgery, you will usually need to spend four to five days in hospital. A small number of people experience severe headaches after surgery. These can be managed with medication and should improve with time. 

You should be able to return to work after around three months. However, a complete recovery may take longer than this. For example, your facial nerve may still be improving up to 18 months after your operation.

The length of time that it takes you to recover may depend on the size and position of the tumour that was removed. The healthcare professionals treating you will be able to advise you. 

If your acoustic neuroma was completely removed, you will not usually require further treatment.

Radiotherapy

Radiotherapy uses safe and controlled doses of radiation (waves of energy) to treat conditions such as tumours and cancer. Radiotherapy cannot always destroy a tumour completely, but it often helps to shrink it and slow down its growth.

If a very small amount of tumour is left on your acoustic nerve after surgery, radiotherapy may be used to treat the tumour.

See the Health A-Z topic about Radiotherapy for more information about this type of treatment.

Radiotherapy can be focused directly on your acoustic neuroma to minimise the damage to healthy surrounding tissue. Depending on the type of radiotherapy that you have, you may need a number of radiotherapy sessions.

Stereotactic radiosurgery

Stereotactic radiosurgery is a newer type of treatment that delivers a very precise dose of radiation to your acoustic neuroma. Stereotactic means locating a point (in this case the position of the tumour in your brain), using three-dimensional coordinates. 

Stereotactic radiosurgery ensures that the maximum amount of radiation is aimed at your tumour and that surrounding tissue is not exposed. It may be given as a single dose or delivered over several sessions.

Stereotactic radiosurgery is performed under local anaesthetic, which means that you will be conscious throughout the procedure but your scalp will be numbed. A lightweight frame is attached to your scalp, and a series of scans accurately pinpoint the position of the tumour. This can then be treated using a precise beam of radiotherapy.

Side effects of stereotactic radiosurgery can include:

• nausea (feeling sick)
• neck stiffness

Nerve damage

In some cases, stereotactic radiosurgery can cause nerve damage, although this may be delayed for several weeks or months after treatment. 

Symptoms of nerve damage can include:

• facial numbness (loss of feeling)
• facial paralysis (not being able to move part of your face)
• hearing loss

Facial paralysis may affect 2 or 3 people in every 100 who have stereotactic radiosurgery. It is estimated that just under a third of people may have hearing loss after stereotactic radiosurgery. 

There may be slightly fewer complications when stereotactic radiosurgery is performed over several sessions rather than in a single session.

Auditory brain stem implants

If your acoustic neuroma is caused by neurofibromatosis type 2 (a rare inherited condition, see Acoustic neuroma - causes) it may be possible to have auditory brain stem implants. These are tiny electrical devices that are inserted into your brain stem (the lower part of the brain that is connected to the spinal cord).

Auditory brain stem implants can be fitted at the same time as surgery to remove your acoustic neuroma. For people who are likely to have complete hearing loss, auditory brain stem implants may enable them to hear some sounds.

This type of treatment is sometimes only available in some specialist centres.

The symptoms of an acoustic neuroma can affect your day-to-life, but more serious complications are rare. See Acoustic neuroma - treatment for the complications that may arise following surgery.

Coping with your symptoms

Some of the symptoms of an acoustic neuroma can be difficult to live with and may affect your quality of life. For example, if your hearing is impaired, you may find your job is affected and communication may be more difficult. Severe dizziness and loss of balance may also affect your job and limit the types of activities that you can perform.

Speak to your GP or specialist if your acoustic neuroma is being monitored but you feel that the symptoms are significantly affecting your daily life. There may be ways of easing your symptoms, such as hearing aids or painkilling medication, or they may indicate that you need treatment to remove the tumour.

You can find more information in the Health A-Z about how to treat some of the problems that are associated with acoustic neuroma. For example:

• hearing loss may be treated with hearing aids - see Hearing impairment - treatment for more information
• tinnitus (the perception of noise in one ear or both ears, or in your head) can be treated with a number of different therapies - see Tinnitus - treatment for more information

Recurrence

It is possible for an acoustic neuroma to return after being removed. The tumour reoccurs in less than 5 in every 100 people.

Hydrocephalus

One of the most serious complications of acoustic neuroma is a condition known as hydrocephalus.

Hydrocephalus occurs when an acoustic neuroma is very large and presses on your brainstem (the lowest part of the brain that connects to the spinal cord). This prevents the cerebrospinal fluid (CSF) that protects your brain and spinal cord from flowing between your brain and spinal cord. This blockage can cause pressure to build up inside your skull which, in turn, puts pressure on the delicate tissues in your brain.

Hydrocephalus can be treated by draining away the excess CSF. It is important that this condition is treated quickly because in severe cases it can cause brain damage. In rare instances, it can be fatal.

See the Health A-Z topic about Hydrocephalus for more information about this condition.