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Acoustic neuroma

Overview

An acoustic neuroma is a rare, non-cancerous (benign) brain tumour. It grows on the acoustic nerve (also known as the vestibulocochlear nerve), which helps to control your hearing and balance. This nerve also runs alongside the facial nerve, which carries information from the brain to the muscles of the face.

Acoustic neuromas grow from a type of cell called a Schwann cell. Schwann cells help to cover nerve cells, keeping them insulated. Acoustic neuromas are therefore sometimes known as vestibular Schwannomas.

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 slow-growing that it will not cause any symptoms or problems.

However, some acoustic neuromas can cause problems with your hearing, balance, and the muscles in your face. Symptoms can vary in severity, and they tend to develop gradually.

An acoustic neuroma is not normally a life-threatening condition. In very rare cases the tumour can grow large enough to press on the brain (see the 'complications' section). However, most acoustic neuromas can be treated before they get to this stage.

 

How common is it?

 

All types of brain tumour are relatively rare. Acoustic neuromas account for eight out of 100 primary brain tumours (tumours which originate in the brain, rather than spreading to the brain from other parts of the body).

Acoustic neuromas tend to be more common in women than in men, although the reasons for this are not yet understood. People who are 30-60 years of age are most commonly affected. This condition is very rare in children.

Causes

The cause of most acoustic neuromas is unknown. There are no risk factors which increase your chances of developing an acoustic neuroma.

It is thought that a fault in a gene which helps stop tumours growing may be responsible, although researchers do not yet know which gene is affected. Further research into the cause of acoustic neuromas is currently being carried out.

 

Neurofibromatosis type 2

 

Approximately 7% of acoustic neuromas are caused by a rare, inherited condition called neurofibromatosis type 2.

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

Neurofibromatosis type 2 usually causes the acoustic neuroma to grow on both sides of the acoustic nerve, rather than just one. This means the hearing in both of your ears is more likely to be affected.

Diagnosis
 

An acoustic neuroma can be a difficult condition to diagnose. This is because your 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.

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

 

Neurological testing

 

You may need to undergo a series of tests to check whether your nervous system is being affected by an acoustic neuroma.

As part of these tests, your hearing will normally be checked (as an acoustic neuroma often affects your hearing). A typical hearing test will involve you listening to a series of sounds which are played at different volumes. You will then have to indicate when you hear a sound.

In some cases, you may undergo a test called an electronystagmography (ENG). This test measures your involuntary eye movements whilst your balance is being tested. These eye movements are likely to be very small, and are not something you would be able to notice yourself. Abnormal eye movements tend to occur when you have a problem with your inner ear (which helps control your sense of balance)

 

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 will allow your doctor or specialist to see the size and position of your tumour.

An MRI scan uses a magnetic field and radio waves to take a detailed pictured of the inside of your body (in this case, the head). A typical MRI scan takes between 15-60 minutes to complete, and is a painless procedure. However, it can be noisy and you may feel slightly claustrophobic.

Treatment

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, and
  • the size and position of your tumour.


The results of any tests or scans you have had will also help determine the best course of treatment.

Your acoustic neuroma will normally be treated by a team of specialists and other health professionals, such as:

  • a neurosurgeon - a surgeon who specialises in operating on the brain, spinal cord and nervous system,
  • a neurologist - a doctor who specialises in treating conditions that affect the brain and nervous system, and
  • an oncologist -a doctor who specialises in treating tumours.


Observation

If your acoustic neuroma is very small, or growing very slowly, then you may be advised to not have any immediate treatment. Instead your condition will be monitored.

Although this may sound like nothing is being done about your condition - it can be the best option, as 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 undergo regular MRI scans so that the size and growth of your acoustic neuroma can be carefully checked. If the tumour shows any signs of growing, or of significantly affecting your health, then other treatments can be considered.

Surgery

Many cases of acoustic neuromas are treated using surgery. In approximately 95% of operations, the acoustic neuroma can be completely removed.

In the remaining 5% of cases, a small part of the tumour may have to remain within your body to help minimise the risk of causing damage to your nerves. If a small part of the tumour remains, this can normally be treated using radiotherapy (see below).

The surgery is carried out under general anaesthetic, and the acoustic neuroma is removed through an incision (cut) in your skull.

Will surgery affect my hearing?

Unfortunately, many people will find that their hearing is permanently affected, to some degree, following acoustic neuroma surgery. Your neurosurgeon will normally work alongside a hearing surgeon during your operation, to help minimise the risk of your hearing being affected.

In most cases, the larger your acoustic neuroma, the greater the risk of your hearing being affected. If your hearing is affected, it will normally only be affected in one ear. If this is the case, you may be able to be fitted with a hearing aid after your operation, which helps by diverting 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 very strong chance that you will completely lose the hearing in both ears following your operation. For this reason, surgery for a tumour on both sides of the acoustic nerve will normally be delayed for as long as possible. Surgery will only be performed if the acoustic neuroma is significantly affecting the rest of your health.

Facial nerve

Surgery can occasionally cause damage to 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 the damage is unavoidable, particularly if your 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, and
  • you have a droop on one side of your face (facial palsy).


Your symptoms may improve following physiotherapy (a type of therapy that helps to improve your range of movement). However, it is important to be aware that some damage to your facial nerve may be permanent.

Recovery from surgery

Following your surgery, you will normally need to spend four to five days in hospital. You should be fully recovered after six to 12 weeks. If your acoustic neuroma was completely removed, then you will not normally require any further treatment

Radiotherapy

Radiotherapy uses safe and controlled doses of radiation to treat conditions such as tumours and cancer. Radiotherapy will not always be able to destroy a tumour completely. It often helps to shrink a tumour, and slows down its growth. If a very small amount of tumour has been left on your acoustic nerve following surgery, radiotherapy may be used to treat the remaining tumour.

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

Stereotactic radiosurgery

Stereotactic radiosurgery is a newer type of treatment that helps to deliver a very precise dose of radiotherapy. You will usually only require a single dose of radiotherapy as part of this treatment.

This procedure is performed under local anaesthetic. This means that you will be conscious, but the relevant part of your body (in this case, your scalp) will be numbed. A lightweight frame is first attached to your scalp. Using a series of scans, the position of the tumour can then be accurately pinpointed and treated using a precise beam of radiotherapy.

Side effects of stereotactic radiosurgery can include nausea and neck stiffness.

In some cases, this form of radiotherapy can damage nerves. You may not experience any symptoms of nerve damage for up to six to nine months following your procedure. Symptoms may include:

  • facial numbness,
  • facial paralysis (not being able to move part of your face), and
  • hearing loss.
Symptoms

When an acoustic neuroma is small, it may not cause any symptoms. Because acoustic neuromas tend to grow slowly, you may only notice your symptoms developing gradually.

Some of the symptoms of acoustic neuromas are outlined below.

Hearing loss - approximately 90% of people with acoustic neuroma experience some degree of hearing loss. Hearing loss normally develops gradually, although in approximately 5% of cases it occurs suddenly. Hearing is normally predominantly affected in one ear.


Tinnitus - this is a ringing sensation in your ears. Again, only one ear is normally affected. Approximately 70% of people with acoustic neuroma have tinnitus.


Vertigo - this can cause you to feel as though you are spinning, even when you are standing still.
Facial numbness, tingling or pain - this can occur if the tumour begins to press on the nerve which controls feeling and sensation in the face (the trigeminal nerve).
 

Headaches - this is a relatively rare symptom, although it can occur if the tumour blocks the flow of cerebrospinal fluid (which helps protect the brain from trauma).


Temporary sight problems - this is again rare, and is also caused by a cerebrospinal fluid blockage.
Ear ache.