neurosurg

Acoustic neuroma

What is an acoustic neuroma?

You have been diagnosed as suffering from an acoustic neuroma. This is a benign growth on the hearing nerve inside the head. ‘Benign’ means that the growth is not a form of cancer and does not spread anywhere else in the body nor does it grow into healthy tissues apart from the nerve from which it takes origin.

What does it do?

The tumour grows very slowly over a period of years so the onset of symptoms is slow. The first symptom tends to be dizziness and this gradually leads on to loss of hearing in the affected ear. These symptoms may continue without much else happening to the patient for many of years.

If the tumour is not diagnosed, it will gradually enlarge and cause problems because of where it is rather than because of its nature. As the tumour slowly enlarges it begins to press upon various structures and may cause symptoms in the surrounding brain or local nerves.

Close to the hearing nerve inside the skull is a nerve called the ‘Trigeminal Nerve’, which transmits the sense of feeling from the face on the side of that nerve. If this nerve becomes involved by the enlarging tumour, feelings of pins and needles may be noticed and later numbness on that side of the face.

As the tumour continues to grow it may also affect the nerve that supplies the muscles on that side of the face and can eventually lead to an inability to move the face on one side. This tends to happen very late, as the nerve that gives movement is very resistant to the pressure from the tumour.

Eventually the tumour reaches a size large enough to cause compression of the brain, and may cause serious difficulty with walking and eventually may become a threat to life.

Fortunately, life-threatening tumours are uncommon and most can be removed surgically.

What causes acoustic neuromas?

It is not fully understood what causes these tumours. In some patients they are due to a rare inherited condition called Neurofibromatosis. In these patients, there is an abnormality in the chromosomes, which carry the inherited patterns that make us individuals. This has not been identified in the vast majority of acoustic neuroma patients who do not have any inherited problems.

Investigation

The most usual way to make the diagnosis is by subjecting the patient to a brain scan that is either an MRI scan or a CT scan. MRI is the best way of detecting small tumours but in the larger tumours either kind of scan is adequate.

Treatment

1. Observation: In elderly or unfit patients a case can be made out for merely observing the patient and doing interval MRI scans perhaps once per year and consider surgery or other intervention if there is a change in size of the tumour. This is not advisable for young patients where a long time is available for the tumour to grow to a size that can eventually threaten life. In addition, the longer one waits the higher the chance that the patient will be less fit for anaesthesia.

2. Stereotactic Radiosurgery: This is a type of treatment only available in certain specialized units in the UK. It involves shining a type of x-ray beam in a highly concentrated form very accurately onto the tumour and this can prevent the tumour from growing. After this treatment a yearly MRI scan is done to follow up whether the tumour is growing or not. The advantage is that no operation is needed. The main disadvantage is that it requires long-term follow-up perhaps for life and if it does not control the tumour surgery may become necessary anyway but the chance of saving the facial nerve may be reduced because of a change in the tumour texture. The risks to the facial nerve and to hearing with this treatment are similar to that of surgery.

3. Surgery: The main advantage is that the procedure is over and done with and apart from a follow-up scan at four years there is no need for long-term scrutiny. The risks of the tumour coming back in our series is roughly one in seventy and a second operation is usually not as complicated as the first.

If the patient is fit for a general anaesthetic then the tumour can almost certainly be removed. This is a highly specialized kind of surgery and the aim is to completely remove the tumour and salvage all the involved nerves.

Our results in Middlesbrough are as good as almost anywhere in the world but the outcome depends on many things, not least the size of the tumour.

Surgery is usually carried out as a joint procedure between a Neurosurgeon and an Ear Nose and Throat surgeon. The operation itself requires a cut at the back of the head and removal of some bone to allow access. The brain tissue is gently held aside, and using a microscope and sometimes a Laser the tumour is removed. To remove the roots of the tumour some bone has to be drilled away and this is usually done by the Ear Nose and Throat surgeon.

Removing a tumour with the laser

During the procedure the tumour has to be gently separated from surrounding structures, which even in the best hands can sustain damage. Fortunately such damage is uncommon and the operation has only a low mortality (2%).

One of the main problems is salvaging the nerve that supplies the muscles of the face. This is because as the tumour enlarges the nerve becomes thinned and may often look only like a very thin band of little fibres. The majority of patients do develop a temporary loss of movement in that side of the face purely from the surgeon manipulating the nerve. Usually this gets better over weeks or months after the operation but in one of our patients it took as long as two years.

The hearing nerve is usually destroyed by the tumour by the time the patient comes to surgery. It is unusual therefore to preserve hearing with surgery although in those patients who have retained hearing on the side of the tumour this can be salvaged in 30%. There is usually however some hearing loss even in those with excellent results.

The length of Hospital stay varies according to how long or difficult an operation is done. In the case of a small tumour, it may be as short as five days, or if complications occur, will be until the patient is well enough to go home.

Preparation

Prior to surgery, the patient is seen by the anaesthetist (who puts the patient to sleep) and any investigations needed are carried out such as chest x-ray, ECG, or blood tests.

When you are admitted to hospital, it is important that you ask the admitting doctor or nurse any questions that you need answering, as they are there to help you.

Some patients with large tumours have obstruction to the normal flow of the fluid that surrounds the brain. The fluid therefore builds up inside the brain and causes raised pressure. This may require to be relieved prior to the main operation by inserting a shunt (like in babies with water on the brain or hydrocephalus). This small operation entails putting in a tube that drains the fluid away into the abdomen (tummy) under the skin. This is an uncommon event and the operation when needed, is a minor one.

The operation

A ‘pre-med’ injection or tablet is usually given on the day of surgery to relax you for the operation. You are then taken to the anaesthetic room in the operating theatre and the anaesthetist gives the anaesthetic. Following surgery you will wake up on the ward unless the operation has been an unusually long one in which case the surgeon may decide to keep you asleep overnight in the intensive care unit and wake you up in the morning.

Post operative care

Most patients experience a degree of headache, nausea and sleepiness after surgery. This may last for a day or two but usually the patient is mobile independently by three to four days in the case of medium to small tumours. With larger tumours, recovery may take longer especially if there are complications although these are uncommon.

This is not a very painful operation but immediate post-operative pain is treated with pain killing injections and tablets after the operation.

Because the facial nerve (that moves the facial muscles) is often not working for a period of time after surgery even if it is intact, special care has to be taken. The eyelid on that side may be unable to close and there is therefore a danger that the eye is exposed because the eyelid is unable to close properly. If the clear tissue (cornea) at the front of the eye is exposed for long, there is a danger that it will dry out and become ulcerated or infected with consequent possible loss of vision. At first, after surgery, the eyelid will be taped down and special artificial teardrops are given to prevent drying.

Another complication that may occur although not commonly, is that swallowing can be affected. The nerves to the muscles of the gullet may have been stretched by the tumour and in some cases of large tumours, they may not function after the operation. Whether this is permanent or temporary depends mainly on the size of the tumour and the degree to which the swallowing nerves are affected. Most patients in whom this occurs can retrain themselves with the help of a speech therapist to swallow more or less normally but this can take time.

Prior to being discharged home, an appointment to see one of the eye surgeons will be arranged if there is facial muscle weakness, in order to have the eye checked. We do not send patients home until this is done. The eye surgeon may feel that the only way to protect the eye is to do a small operation to close the lid at the corner to reduce the surface area of the exposed cornea.

Occasionally the brain fluid that surrounds the brain (cerebro-spinal fluid) finds a way out of the head either through the wound or into natural spaces in the skull bone. The fluid then can leak out of the wound, or can come down the nose. This usually responds to insertion of a fine tube in the spine to lower the fluid pressure (spinal drain), or in some cases, requires the wound to be re-opened to seal off the fluid spaces. This procedure is a minor one however and does not usually require disturbance of the brain, only the outer tissues.

After Discharge from Hospital

After you return home it is wise to ensure that you have someone staying with you for a week or so. You will not be fit to go ‘charging around’ doing housework or shopping for some weeks. It is important to rest after the surgery and many patients have a feeling of fatigue or may feel a bit down in the first few months after the operation – this is quite normal.

When you go home from hospital, you will be given a supply of painkillers as some residual discomfort may occur in the wound as it heals. If you are in severe pain, (which you should not be), contact your family doctor but this is very unlikely.

Some patients experience headaches for a variable period of time after surgery. The cause is unknown although it is not due to any serious condition and will resolve by itself given time, requiring only proprietary painkillers such as paracetamol (Panadol) until it does.

If the wound becomes painful, red or swollen or discharges any kind of matter you should seek further advice from your own doctor or from the ward as such symptoms can indicate infection, which may require antibiotics.

This type of surgery should not jeopardize your ability to drive a car, and but you need to seek the advice of the DVLA (in Swansea) and your insurance company before you resume driving. If you have their permission to drive then you can resume this activity by about six weeks. After your return home you should try to do slightly more every day so that by six weeks to three months you have returned to your normal level of activity. A normal sex life can be resumed within weeks.

Above all remember that the hospital staff are there to help you even after discharge and if you are worried telephone the ward and talk to the nurse in charge or the duty doctor.

You will be seen in the outpatient clinic at around three months post-operatively and this appointment will be sent to you direct. If no appointment arrives within six weeks telephone the hospital and make sure.

Follow-up

We usually follow up patients following Acoustic Neuroma surgery for a period of four years. At the end of that time a brain scan is carried out to exclude the possibility of the tumour coming back. If the four-year scan is clear then the chance of late recurrence is remote and you can consider yourself cured. To date in our first one hundred and forty patients only two have had the tumour return, and it was successfully removed at an early stage in both patients.

Where can I get more information?

1. Most libraries contain some medical books but it is difficult to know how up to date these might be.

2. Your GP. Your own family doctor may have experience of other patients with similar problems and he at least will give you unbiased advice about what is best for you.

3. The Internet. There are a number of web sites that can be accessed by searching on the web. The main drawback is that there is no guarantee that the information from them is accurate or unbiased. If you are happy that the information is from a good source that is OK but one has to be careful of unrealistic claims.

There are patient associations such as the British Acoustic Neuroma Association, which is a source of support for sufferers of this condition.

4. Your surgeon. If after you have seen your surgeon for a consultation, you are still unsure and undecided make another appointment to see him and make a list of questions to take with you. It is important to have a clear idea of how much of this surgery he undertakes and what his results are and he should be able to tell you exactly what his figures are for outcome of individual sizes of tumour.