Acoustic Neuroma what is it?
An acoustic neuroma is a type of brain tumour occurring in one person in every 50 100,00 and accounts for 6% to 10% of all brain tumours. They are benign and usually slow growing. Their early symptoms are deceptive because they are like those with many less serious problems. The cells that form an acoustic neuroma are called Schwann cells and make up the lining of the eighth cranial nerve as it passes through a tiny canal, which connects the inner ear to the brain. This canal carries the nerves of hearing, balance and one of the facial nerves. Unknown events lead to an overproduction of Schwann cells, which as they multiply, form a small tumour, which fills the canal. The tumour is also known as a vestibular Schwannoma.
How is it found?
The diagnosis of acoustic neuroma is usually made after a patient reports one-sided hearing loss, balance problems or tinnitus and the appropriate tests are carried out to locate the cause. CT and MRI scans are used to make the final diagnosis.
The main treatments are Watch and Wait (monitoring) Surgery, Radiosurgery or Fractionated Steriotactic Radiotherapy. Normally small tumours are monitored through a Watch and Wait process while larger ones will be treated with surgery, radiosurgery or radiotherapy.
Watch and Wait.
If the acoustic neuroma is small and the patient has adjusted to living with the symptoms, then it may be appropriate to monitor the tumour through periodic scanning, either annually or less frequently, following specialist advice. The growth rate of an acoustic neuroma gives the specialist and patient time to prepare for treatment should it eventually prove necessary.
The surgery is often carried out by a two specialist team made up of a Neurosurgeon and an ENT surgeon. Removal of the tumour may be approached from behind the ear (sub-occipital or posterior fossa), the mastoid and inner ear structures (translabyrinthine), or above the ear (middle fossa). The choice depends on the location and size of the tumour, degree of residual hearing and the surgeons operating preference.
Instructions about care at home, activity level, and follow-up appointment will be given at the time of hospital discharge.
There may be some lasting effects from surgery.
Hearing is often lost on the affected side. As hearing is often poor before surgery this may not produce a major difference. It is possible to lead a normal life while only having hearing on one side but there are hearing aids available that can improve hearing.
The tumour, as it grows stretches the facial nerve and during surgery the function of the nerve is monitored carefully. However, sometimes the nerve may become bruised or swollen as it is separated from the tumour. Patients may suffer a degree of weakness in the face initially but, provided the facial nerve remains in one piece, this will improve over time, although the extent of improvement is variable This may affect the ability to close the eye fully and the mouth may droop on one side . As long as the nerve is intact time and exercise will aid improvement. A small machine called a trophic stimulator can also be used to stimulate muscles and nerve activity.
There may be some problems with balance immediately after surgery but these will usually improve with time and the help of a physiotherapist.
A number of people with acoustic neuroma experience tinnitus. This frequently remains unchanged after surgery.
Radiosurgery is a technique for treating brain tumours that is available in the UK in a few specialised neurological centres. The two main methods of carrying out radiosurgery are by gamma knife and by modified linear accelerator (linac). Both of these procedures use a high-energy dose of radiation that can be focussed on a very precise point within the brain. Whereas the linac uses only one beam of high-energy radiation, the gamma knife uses 201 energy sources that combine to form a high-energy point at the focus, each source being too weak to damage the healthy brain tissue in the path of surrounding areas. The linac is a general radiotherapy device that can be used for radiosurgery. The gamma knife is a device that has been designed specifically for radiosurgery. Stereotactic surgery involves the use of a frame is which is fitted to the patient. The frame lets the surgeon take scans and build up a model of the head on a computer and use this to design the best treatment for anywhere inside the head. Radiosurgery may be completed in one visit and usually does not require an overnight stay. Some people are able to return to their normal routine immediately following treatment without some of the side effects of open surgery. This approach may be suited to deep seated tumours within the brain such as acoustic neuromas that may be difficult to reach by other methods without causing damage to the surrounding healthy brain tissue.
Fractionated Steriotactic Radiotherapy (FSR)
Fractionated Steriotactic Radiotherapy is given in a similar way to a course of medicine. The doctor writes a prescription like take this many x-rays to this part of your body in this many days. Each separate bit of treatment is called a fraction. The treatment is spread out over a number of days or weeks and given in lots of equal sized bits and this is called fractionated treatment. A frame is used, which is fitted using a gum shield made to fit your upper teeth or gums. This ensures that the frame sits in exactly the same position each time it is worn. A rest is made for the back of the head and straps are used over the top of the head to hold the frame firmly in place. The radiotherapy treatment uses x-rays that can be moved around you to point to exactly the same point in your head from many different angles. Not all acoustic neuromas are suitable for treatment by radiotherapy and the best individual course of action should be discussed with your consultant.
There may be lasting effects from radiosurgery or radiotherapy but they are rare. However this form of treatment does not remove the tumour but it usually stops it growing and it will shrink. This means that regular scans will be required to ensure the tumour does not continue to grow or start to grow again.
The above information was obtained from the BANA (British Acoustic Neuroma Association) leaflet ‘Some answers about Acoustic Neuroma’ and AMNET’s information leaflet to whom our thanks are offered. Our thanks also to Caroline Batt and Ella Pybus who produced these notes.
For further information contact Ella Pybus, 21 Plough Lane, Sudbury, Suffolk, CO10 2AU. Email firstname.lastname@example.org web www.meningiomauk.org. Please note these are general notes which may or may not apply to you. Please discuss them with your Doctor or Medical Advisor.
AMNET stands for Acoustic Neuroma and Meningioma Network so we also include a definition of a meningioma.
A meningioma is a tumour of the meninges which is the name given to the protective lining of the brain and the spinal chord. It can occur in any part of the brain or spinal chord but the commonest sites are at the surface of the brain , either over the top or at the skull base. Meningiomas are almost always benign and do not spread. Malignant (cancerous) meningiomas are extremely rare. It is also possible but rare to have more than one meningioma. What are the symptoms?
These can vary greatly, dependent on where the tumour is. Symptoms are caused by brain displacement or compression, not by invasion. However these tumours can be so slow growing that they may go undetected for years. They can grow in and around the cranial nerves that control function so that eyesight , taste, smell ,sensation (numbness) swallowing or other movement may be affected. They may cause fits, or muscle weakness. Sometimes sudden unexplained and/or recurrent severe headaches are the first symptom. A CT or MRI scan will be done to find out the exact position of the tumour. The MRI scan usually includes injection of a contrast (a short-acting dye) in order to determine the exact position and size of the tumour.
Treatment of Meningioma.
The treatment for meningioma depends on a number of factors including your general health, the size and position of the tumour and the rate of progression of the symptoms.
The possibilities are:
For meningiomas located near the surface of the brain ,surgery is often the best option. For meningiomas that are deep (cavernous sinus ,medial sphenoid wing, parasellar, skull base and clivus) complete surgical removal may not be possible or it may involve too much risk to the cranial nerves or blood vessels. In addition, meningiomas sometimes recur, especially those that are atypical ( on the borderline between benign and malignant). Radiation therapy may then be used to control their regrowth, whereas radiosurgery is increasingly used instead of surgery to control small meningiomas.
Radiation therapy treatments
SRT steriotactic radiotherapy or steriotactic radiosurgery
Highly focussed radiation is given ,which precisely targets the tumour with little impact on healthy brain tissue. Radiation is administered in smaller individual doses over a number of weeks ( often 30 sessions given over 6 weeks). This allows the overall total dose to be higher than in standard radiation, because it allows normal brain tissue to recover better. It stops tumour growth in the vast majority of cases and in some people it may even cause the tumour to shrink. Each treatment is called a 'fraction' therefore this type of treatment is sometimes called ‘fractionated’ therapy.
This can be given either with a gamma knife or a modified linear accelerator. It is not thought suitable for larger tumours. Gamma knife radiosurgery is generally a single treatment planned and delivered in one day. Fractionated radiosurgery SRT (see above) is more commonly employed as it is considered safer for most patients.
Watch and Wait.
Do nothing, but monitor the tumour on a regular basis e.g. an annual MRI scan. This can be an option because meningiomas are slow- growing and may be preferable if the tumour is not causing problems, particularly in older patients.
Hormonal therapy and chemotherapy
These options have been tried in a small number of patients when meningiomas recurred despite surgery and/or radiotherapy. It has met with some success but is still on trial and in its early stages.
Further information about meningiomas can be obtained from Ella Pybus who produced these notes.
The Meningioma Association UK tel: 01787 374084. Ella Pybus, 21 Plough Lane, Sudbury, Suffolk, CO10 2AU. Email email@example.com web www.meningiomauk.org.