Radiation treatment options

GK frame video
GK frame installation
FSR dental frame at SIUH
FSR dental frame at SIUH in use
FSR thermal mold at SIUH
FSR thermal mold at JHH in use
Gamma Knife video Single-shot (SR) Dental mold (FSR) Dental mold in use Thermal mask (FSR) Thermal mask in use

Introductory comments about acoustic neuroma treatments

The options open to AN patients are basically:

  • surgery,
  • radiation,
  • watch & wait (no treatment).

Before deciding on the type of treatment you want, ensure that you know all your options.  We recommend that you start with the treatment options page. This page is for patients who are contemplating radiation. Different pages explore surgical and wait & watch options.  You are strongly advised to read them all before making any decision.

Reasons to choose radiation rather than surgery

There are many good reasons for choosing radio treatment, however, you must recognize that, whilst the AN will be killed and stop growing and in many cases will shrink significantly, it will still be there; albeit in residual form. So, for those people who insist that they "want the thing out of their heads" this is not an option.

However, for the majority of people who are happy if the AN is prevented from doing any further damage and who wish to avoid the negatives of micro-surgery, there are two main radio treatment choices plus a number of variations.

Typical advantages are :

  1. Radiation is typically an outpatient procedure, though some patients may stay in the hospital overnight. The radiation session itself takes a few minutes. Some procedures are done in one session others take several sessions.
  2. There is usually no need to take time off from work.  (Some people are treated on their way to or from work)
  3. There is no recuperation or convalescence period after treatment.
  4. There are usually no immediate complications. In the medium term there may occasionally be complications, (usually minor) discussed below.
  5. Radiation has the best record for hearing preservation and practically never produces any facial paresis (1).
  6. There is no recorded case of this treatment causing death
  7. There is no chance of contracting diseases such as meningitis(2).

Introductory comments about radiation treatments

Radio treatments fall into two broad categories by treatment method and three more categories by generic machine used. There are also a number of sub-divisions of each, so making an informed choice can be quite a time consuming affair.


You might have noticed that we have carefully used the term "Radio-treatment" throughout most of this site. However, elsewhere, you will more usually come across the terms "radio-surgery" and "radio-therapy". We have tried to avoid these terms, as there is a degree of controversy about which is correct in what situation. If you wish to learn more about this issue, click  here.

The Treatment Methods

The two methods are single session and fractionated or multi-session. The difference as you may guess, is that in the first, the treatment is given in one treatment session, whilst in the second, the total treatment is divided into a number of "fractions" and given over a period of days, weeks or even months.

  • Why Single Session? The advocates of single session treatment argue that the main reason for fractionation in cancer patients is that cancer cells are best killed when dividing. Cancer cells divide frequently; therefore fractionation gives the Doctor the chance to kill off more of them, thus giving a better chance of a cure. This isn't the case for benign tumours; therefore there is no case for fractionation. Furthermore, each time the patient is taken in and out of the locating device, there is an increased risk of misalignment. This would also clearly reduce the chances of a good outcome.
  • Why Fractionation? Radio-surgeons have long known that fractionation (or at least the time between fractions) allows healthy tissues to recover, whilst the tumour tissue remains "damaged". However, whilst this was considered important for cancer patients where very much higher total radiation doses are given, until relatively recently, it was not considered necessary or even beneficial for the treatment of benign tumours such as AN's. This view was to a certain extent borne out by the results obtained by a small number of Doctors who used Cancer derived treatments to treat AN's. These did not (historically) appear to be markedly different to those obtained by single session radio-treatments. More recently, AN specific, fractionated treatments using a small number of fractions and a relatively low total dose have emerged. These are sometimes called "hypo-fractionated" treatments. The results obtained from these appear to support the case for fractionation.
  • Who is Right? Like so much else connected with AN treatment, "that depends". You will have to read the reports, both from patients and Doctors, consult treatment providers directly and then decide which is right for you. At the end of the day, your decision might be dictated by "the golden rule" - "Find the best expert you can" rather than by a very strong preference for or against fractionation.

The Machines

There are three fundamental machines (again, with a number of sub types!), which are used for Radio-treatment. They are:

  1. Gamma Knife (GK) The oldest of the machines in terms of principles, but today's GK machines have evolved considerably from the original. There is over 30 years of experience in the use of these machines in treating Brain Tumours of all types including AN's. All GK machines use a Cobalt 60 radioactive source to provide the treatment radiation and a head-frame attached by pins, which clamp onto the patients skull. A local anesthetic is used to ensure the patient feels no pain, although according to some patients, there is minor discomfort once the frame is removed.
    The treatment is given by a pattern of 201 individual fine beams of radiation all of which converge on the tumour so that the AN gets the full dose of radiation, whilst each of the tissue areas the beam passes through on the way in and out, only get a small amount of radiation.
    Each of the treatment beams can be individually adjusted, so that a treatment session may result in many more than 201 beams passing through the AN, enabling the Doctor to plan a treatment which conforms as closely as possible to the AN being treated.
    Whilst GK is almost always single session, we know of one Doctor, (Georg Noren of Providence, Rhode Island) who provides fractionated GK (FGK). Since this involves wearing the screw on head-frame for up to a week, not many (less than 20 in 4+ years) people have been treated by this method.
  2. Linear Accelerator (Linac) The Linear Accelerator or Linac generates its treatment radiation electronically, so, unlike the GK machine, when it is switched off, there is no radiation. Unlike the GK machine it uses a single beam which can be manoeuvred around the patient and turned on and off to achieve a similar concentration of radiation on the AN to that which the GK machine achieves using the 201 individual beams. Also, the beam passes through a collimator, which can be used to narrow or widen the beam and focus it to conform closely to the tumour shape and size.
    Unlike the GK machine, there is no screw on head-frame used for Linac treatments. Instead, either a relocatable head-frame using an upper dental mould (the "Gil-Thomas" head-frame invented by a team at the Royal Marsden Hospital in London) or a custom moulded facemask may be used.
    There are a number of variations on the Linac machine, which can confuse patients. The best known are the "Peacock" which is essentially a modified collimator, and the "Cyber-knife" which uses a miniature Linac machine attached to a robot arm which is guided using x-ray imaging to check the position of the patient between each treatment shot. However, in use, the Cyber-knife appears to be used in a fashion, which more closely mimics an electronic Gamma Knife than a conventional Linac.
    Although there are a (very) few places which use Linac for single shot treatment, it is generally used for FSR.
  3. Proton Beam As the name suggests, this machine uses a beam of protons to kill the tumour. A Cyclotron is used to generate the beam. Theoretically, this is preferable to the X-Rays used by the Linac and GK machines as the protons can, in theory, be stopped before they exit the AN, thus reducing damage to normal tissue. However, to date, very few people have been treated by this method and the results known to us are not statistically good. People considering this method should do plenty of research to ensure that they have the very latest information.
    The Cyclotron costs far more then either a Linac or Gamma Knife installation, it is understood that the one at Loma Linda in California cost $40 million. The only other providers we are aware of are MGH in Boston and in Belgium.

Radio-treatments -- Further Detail

Gamma Knife

Gamma Knife is sometimes said to be "like a big Mac" - that is, the same wherever you get it. Please beware, as this isn't true. Just as with other AN treatments there are variations in the machine, in the software used for planning and in the experience and preferences of the treatment team. So, if GK is your choice, don't just assume that the local GK centre (if you have one) will match results obtained by the best, they may not.

Our advice is that the two factors that matter to the average patient are the historic outcomes achieved by the particular centre and the dosage used. Other issues such as software standard used, planning protocols adopted and so on, whilst of academic and professional interest are beyond the average patient to assess. And, at the end of the day, if Centre "A" produces excellent results with (say) the 2001 release of software those results are more important than the fact that Centre "B" has the 2004 release software but can't provide its statistics.

The one thing that can be understood by patients however, is "total dose". It is a general rule of thumb that a lower total dose results in (statistically) lower side effects. Many people therefore conclude that if the control rates of two GK centres are similar, then the one with the lowest total dose will be the one with the lowest side effects. There are however two things to beware of when using this logic:

  1. Were the control rate figures you are being given achieved with the low dose you are being offered, or with an older higher dose treatment?
  2. You can only use the total dose figures to compare like with like. In this case one GK centre with another. You cannot directly compare a GK total dose figure with an FSR total dose figure. This is because the "Isodose" lines used for planning differ for the two methods. As a general rule, if both have the same total dose quoted, the FSR centre total dose will in reality be lower - BUT, this may not always be the case.

Fractionated Stereotactic Radio-Treatments (FSR)

FSR divides into two basic types:

  1. "Traditional" treatment derived from Cancer treatments. This typically uses between 20 and 30 fractions and a total dose of up to 5000 rads. Such treatment has been around for some 15+ years and is still offered at established centres such as Massachusetts General Hospital. Some centres have reduced their total dose in recent years.
  2. "Hypo-Fractionated" Treatments. These typically use 3 to 6 fractions and a total dose of between 2000 and 3000 rads. Dr Gil Lederman pioneered this type of treatment in the early 1990's whilst at Staten Island University Hospital, New York .  (Dr Lederman is now at The Cabrini Hospital, New York where he continues to offer this treatment)  The late Dr Williams introduced his own variation on this protocol at Johns Hopkins (Baltimore) a year or so later.  Dr Rigamonti continues to offer the same treatment at JHU today.

Hypo-fractionation has several advantages over simple FSR. These are:

  1. Lower total dose.
  2. Better control rates.
  3. Virtually zero side effects - Facial Paresis (1) is virtually unknown, hearing damage is minimal and in some cases, hearing improves post treatment.
  4. Treatment can be completed much quicker. This is of particular importance for those patients who have to travel to find a suitable treatment centre.

Further Issues:

At an even lower level of detail, the issue of time between fractions is debated. Radiological theory says that as long as there are 18 hours between fractions, the healthy tissue can recover and any longer gap offers no advantage. However experience now suggest that the theory is inadequate in some way.

Dr Gil Lederman's pioneering FSR treatments were originally offered on the basis of fractions given on a daily basis or with a greater gap if it suited the patient's circumstances better. For example, some of his patients opted for one treatment a week to suit their working patterns. An analysis of the outcome for the first 200 patients treated revealed that those who had 48 hours or more between fractions had far better hearing outcomes than those who were treated on a daily basis. Now Dr Lederman treats everyone on the basis that they should have at least 48 hours between fractions. Whist Dr Lederman has demonstrated by far the best hearing preservation results of any AN treatment in the world, many experts do not accept that it is the bigger gap between fractions which gives this advantage.


Cyber-knife treatments all fall into the "Hypo-Fractionated" category. However, as alluded to elsewhere, in other respects the treatment is more like GK. This is because the robot arm moves the Linac to a particular position; gives a dose whilst stationary; moves to a new position, gives a second dose and so on.

Proponents of Cyber-knife will claim that this is an advantage, others quote it as a drawback. Once again, our advice is to ignore this debate and look at the results achieved at the centre you are considering. If they appear to be good, then that is the important fact.

An Italian Cyber-knife center in Milan (Italy) has an interesting 360� Cyber-knife virtual tour.

Proton Beam (PB)

Whilst offering the theoretical advantages outlined above, experience with this treatment is so limited that we are unable to offer any further detailed information. Should any reader either have such information or have personal experience of PB treatment for their own AN, the authors would be delighted to hear from them in order to update this section in due course.

An interesting series of surveys of failures from radiation treatments is being carried out from contributions to various acoustic neuroma forums. The first survey, on FSR treatments, is here. Others will follow covering GK and Cyberknife.

The Accuracy Debate

Sometimes, treatment centres will claim that their treatment machine (Gamma Knife, Linac, Cyber-Knife) is "more accurate" than the others. We have seen "evidence" that shows each of these three common machines to be the most accurate!

It is our opinion that such a debate is meaningless. Why is this? Well, we also see evidence of excellent results from experts using each of the machines (and less good results from the less expert) and at the end of the day, it is the results which count. Once again our advice is find the centre/treatment provider whose results look best for you and not to worry too much about how that is achieved.

After all, if you are buying a painting, you don't worry that the artist may have chosen the wrong sort of brush; you judge what is on the canvas! (And I can't produce a Leonardo, even if you give me the very brushes used to paint the Mona Lisa!)

The Great Terminology Debate

As mentioned in the introduction, there is a great debate over the correct name for Radio-Treatment. Whilst to we patients this is of less importance than "will it work for me", curiosity makes most people want to learn a little about it. To do this, we need a short medical history lesson.

Over 50 years ago now, radio-therapy was used for non-invasive treatment for many conditions. This involved irradiating a lot of the body in addition to whatever was being treated. For some conditions, this was actually beneficial, for many however, it caused more problems than it cured.

In the 1950's a Swedish Surgeon turned his considerable intellect to finding a way to use Radiation in a focussed and controlled manner with surgical precision to treat lesions in the same way as a knife, but without the need to cut the patient open. This was Dr Leksell and his machine became the prototype Gamma Knife. He coined the term "Radio-Surgery" to describe the treatments he gave using it and to differentiate this treatment from the crude radio-therapy treatments offered up to that date.

More recently, with the invention of the Linac and its adoption as a medical instrument, people have offered "radio-surgery" using these machines rather than GK machines. The GK machine makers (and by extension, the Doctors who use such machines) have tried to claim at various times that Radio-surgery is:

  1. only a "one session" treatment,
  2. only possible with a GK machine,
  3. a high precision application of radiation in a controlled manner,
  4. a combination of the above.

As patients we consider this to be an attempt to retain a competitive advantage for selling the GK machine, rather than a substantive issue. Our view is that if there is precision, it is reasonable to call it "radio-surgery", but at the end of the day, we don't mind what you call it as long as it works!

Other situations that involve radiation

  • Debulking

    A technique called debulking uses any of the microsurgical approaches as the first step in a two step process. In case of regrowth, the surgery is followed up with a radiation treatment to arrest the tumor. Oftentimes it is used with large tumors when the goal would be to primarily preserve the facial nerve.

Short term and long term outcomes

Radiosurgeons generally claim a very low rate of failure, typically less than 5%, often less than 2%. "Failure" in this case is defined as continued growth of the tumor. Temporary swelling, occuring up to 2 years post radiation, can be mistaken for real growth. Swelling is an inflammation, increasing the size of the tumor. Growth is an increase in the number of tumor cells. See an interesting patient survey of radiation treatment failures.

  • Hearing Loss - This is less common with hypo-fractionated treatments.
  • Tinnitus (3) - This is unpredictable, for some, tinnitus is reduced after treatment, for others it is not.
  • Vertigo, dysequilibrium, and imbalance - This is rarely an issue with FSR and normally only an occasional short term issue with single session treatments.
  • Facial Numbness, Weakness, and Twitch - Almost unheard of (but not impossible)
  • Headaches - Very rarely (almost never) reported.
  • Swelling of the AN 3 to 6 months after treatment.  Any Radio-treatment may produce a temporary swelling of the AN in this period, however it seems to occur more often with single sessions treatments.  The patient feels "odd" (exact symptoms vary) and in occasional cases experience sudden hearing loss.  This is usually temporary and very short term, but many Doctors treat with Prednisone or a similar steroid to ensure early resolution.
  • Dry eye (4) - Practically unheard of.
  • Hydrocephalus (5) - A small percentage of patients (the same percentage as for surgery) will suffer from hydrocephalus.  This is cured by a simple operation to place a "shunt" which relieves the excess pressure by draining the fluid.


  • Fractionated Stereotactic Radiosurgery (FSR) centers
    • Cabrini Hospital New York (Dr Lederman)
    • Johns Hopkins, Baltimore (Dr Rigamonti)
    • Stanford Cyberknife Center (Dr Steven Chang)
    • CyberKnife support forum where you can send your questions to CyberKnife doctors.
  • Gamma Knife (GK) centers
    • San Diego Gamma Knife Center, La Jolla (Dr Ott). Contact: Marcia Morrell Patient Care Coordinator, phone: 800 347-0038. Site:
    • University of Pittsburg Medical Center (UPMC is a well known radiosurgery center for ANs. They have published several peer-reviewed studies on the subject.)
    • Providence Rhode Island - Dr Georg Noren The Acoustic Neuroma Association (USA). There is a lot of useful information on this site and a guest book as well as a very active mailing list for patients. The Seattle (WA) Acoustic Neuroma Group - SANG. The AN Patient Archive site, full of information and patients' stories.

No medical decision should be based solely on information provided here. See disclaimer

1 Facial paresis is the medical term for facial paralysis, usually partial, often temporary, which results in a lopsided face and/or difficulty in closing the eye.

2 Meningitis  is an infection of the fluid of a person's spinal cord and the fluid that surrounds the brain.  It can be fatal, especially in the young.  Go to   or for more information.

3 Tinnitus is a constant buzzing or ringing in the ear, often experienced by AN patients (and many non-AN patients for various reasons).

4 Dry eye is a condition where the surface of the eye is insufficiently lubricated with tears. Often the result of the eyelid failing to close completely.

5 Hydrocephalus is pressure on the brain caused by a problem with the flow of cerebrospinal fluid (CSF).  This can be due to blockage of the ventricles or to a thickening of the fluid.