The middle fossa approach was developed later, removing the tumor through an opening above the ear. This approach was developed in an effort to preserve hearing in patients with smaller tumors.

The similar retro-sigmoid and suboccipital approaches enter the posterior fossa well behind the ear. These methods also offer an opportunity to preserve hearing in small and medium sized tumors.

In the 1970, surgery was able to save your life. In 1980, surgery was often able to save your facial function. In 2000, saving facial function is the norm, and saving hearing is possible, with the probability depending upon the size of the tumor.

California State University at Chico has an excellent 3-D model of the human skull may help you visualize the surgery, and here's another skull model from the Unversity of Iowa.

Radiation is measured in either "rads" or "grays." Treatment in the 1970's generally used 18-20 gray, and sometimes as much as 40 grey. This has been shown to provide long-term tumor control almost as good as surgery. However, the rate of facial and trigeminal nerve damage was much worse than surgery. One study showed that although hearing preservation was good immediately after radiosurgery, over the following ten years after treatment, the number of patients with "useful hearing" declined from 80% down to 14%.

In an effort to reduce the side-effects, treatment in the late 1980's generally used 14-16 gray, but the rate of facial and trigeminal nerve damage remained worse that surgery. The long-term rate of tumor control for this lower level of radiation is not as well known because it has been used for a shorter period of time, but appears to be comparable.  In the 1990's, some single-dose radiation treatment centers are reportedly using doses as low as 12 gy in a search for the lowest dose which controls the tumor.

In 1991, the NIH issued a "concesus statement" that radiotherapy was recommended only for patients who could not tolerate surgery, because at that time, radiosurgical outcomes were not as good as microsurgical outcomes. Some of the techniques used in 1991 and earlier included Fractionated Radiotherapy (FR) and single-dose Gamma Knife (GK).
 

Low-dose single-shot GK still has rates of facial paralysis and trigeminal neuropathy which are significantly worse than microsurgical results.  And one local radiosurgical hospital offers the weak comfort that, "Hearing loss, when it occurs, happens slowly so that the patient has plenty of time to get used to it."  With superior new radiation techniques, single-dose GK need not be considered in a patient's search for treatment.

In the mid-1990's, the first patients were treated, on an experimental basis, using a combined technique called Fractionated Stereotactic Radiotherapy (FSR) which uses stereotactic methods to minimize radiation dose to the normal tissue, while also spreading the radiation doses over one to four weeks (most commonly two weeks) instead of giving the radiation in a single dose. In 1998, the technique was first applied to large groups of patients.  I've been told the maximum doses are on the order of 25 gray, and I think some centers use as little as 15 but I'm not sure.

Part of the idea behind FSR is that the small doses injure the healthy tissue less, and time between doses allows the tissue to heal a little before the next shot.  I assume the dose is increased because the tumor heals a little also.  Some of the types of FSR offered are:

• LINAC, a miniature linear accelerator that moves a beam of X-Rays in an arc around the head, always keeping the tumor in the focus of the beam but limiting the time the healthy tissue is in the radiation path.
• PEACOCK, a technique like LINAC but with a variable waveguide that conforms to the shape of the tumor.  The manufacturer claims this provides superior control of the beam for larger, or more convoluted, tumors.
• FGK, or fractionated Gamma Knife, is a recently developed technique that uses the old Gamma Knife machine but fractionates the radiation dose.  Has the advantage of more accurate aim that the two above methods, although I've read some claims that the small waveguides of GK are inferior for large tumors.

(I should also mention that Loma Linda performs radiation treatment with a stereotactic Proton Beam, and I'm not sure whether or not they're fractionating the proton radiaton at this time.  I believe this is the only center performing this method of treatment.  The advantage of proton beams is that unlike X-rays or gamma rays, the majority of the proton beam does not pass through the tumor, so it only irradiates the brain on one side.  I don't know anything about their success rate.)

The results for FSR look very promising. Long-term tumor control remains unknown because of the short amount of time this technique has been used in large groups, but short-term tumor control is comparable to the older, high-dose techniques. Facial nerve preservation is reportedly 100%, hearing preservation is reportedly as high as 80%, and there have been few reported cases of trigeminal neuropathy. One radiosurgeon goes so far as to call it "criminal" to perform microsurgery for AN given these statistics.

The leading proponent of radiotherapy in the U.S. is Dr. Gil Lederman of University Hospital at Staten Island. If you read his published papers with a critical eye, you can see that Dr. Lederman is an FSR evangalist with what must be uncharitably described as a messiah complex.

Dr. Lederman claims to have a 100% success rate, despite the published account (from the pro-radiosurgery AN Archive) of a patient who nearly died from side-effects of radiotherapy.  The information missing from most studies of radiotherapy is, "How many patients did not complete the full series of FSR treatments because of complications, life-threatening or otherwise, which developed during treatment?"  Since these patients voluntarily stopped the radiation treatment, Staten Island and at least one other major radiosurgical hospital do not consider their experiences failures worthy of reporting in medical jounals.

This DOES NOT mean the technique doesn't work for the majority of patients, but it is still unfair to pretend these unhappy patients do not exist.  During clinical trials of new drugs, the dropout rate is normally reported because it is considered to a very important measure of patient tolerance of drug toxicity.  Any study of radiosurgical outcomes must include the rate of "dropouts" to be valid.

Further, Dr. Lederman may really have found the holy grail for AN treatment, and may well have earned his messiah complex.  I don't know.  But Dr. Williams of Johns Hopkins has performed almost as many FSR treatments for AN as Dr. Lederman, and he is much more open and straight-forward about the risks and side-effects.

This is a case of comparing apples and oranges. The radiosurgical techniques used 30 years ago were crude by today's standards, and used much higher levels of radiation.  The single-shot radiation dose has declined from 18-40 gray in the 1970's, to 14-16 gray in the early 1990's to as little as 12 gray at some GK centers, but the single-shot techniques used today (2000) STILL have higher rates of complication than surgery.

UCSF has pointed out that studies in animals show poor or no tumor control for a dose of 10 gray, which dampens some of the enthusiasm about the long-term rate of tumor control with low-dose single-shot GK, another reason to avoid this method of treatment.

Fractionation (FSR) helps the healthy tissues tolerate a higher radiation dose, but little is known about the long-term results.  AN tumors have a peculiar radiobiology (see below).  Does the fractionation also increase the tumor's tolerance of radiation?  Does the higher dose make the long-term side-effects look like single-shot GK?  Trigeminal and facial nerve damage sometimes showed up years after treatment with single-shot GK, so we won't know the rate of long-term complications until 2003 (5 years of large-scale FSR treatment) or more likely 2008 (10 years of large-scale FSR treatment).

Again, this DOES NOT mean the technique doesn't work, but these apples and oranges statements by some of the top radiosurgeons in the nation are not completely fair statements. The data in favor of FSR looks VERY good on its own, although the track record is short. Embelishing the facts is unnecessary.

Both of the above statements are false.

There have been a very small number of documented cases of cancer, (see UCSF link) sometimes fatal, developing after irradiation of AN and other benign tumors. Given the large number of patients treated, and the small number of cases of cancer which have occurred, the risk of developing cancer must be quite low. Further, the risk may be even smaller with fractionation, because the DNA has a little time to heal between doses.

Young patients present a special case. Their risk is higher because of a longer future life-span for complications to develop. In other types of radiation, both therapeutic and industrial, cancer has been documented as arising as long as 25 years after exposure. Still, the risk of developing cancer from FSR is probably very low even for these patients.

I can discount the microsurgeons' statements about cancer as being due to ignorance.  Radiotherapy is not, after all, their field. Radiosurgeons, however, should know better, and should not be telling their patients that cancer never happens. Let the data speak for itself: the risk is clearly small so why claim that it is zero? As before, embellishing the facts is unnecessary and undermines crediblity.

One radiotherapist told me that "there has been no documented case of cancer developing from FSR treatment for acoustic neuroma." Which is probably a true statement, given the short period of time and small number of patients treated for AN with FSR. This doctor was quickly agreed the risk existed, but was probably very small. That's the honest way to go about things!

Some AN tumors swell during radiotherapy. Most reportedly do not. However, since MRI's are still so expensive, we don't know what happens inside patients' head.  We really don't know how often swelling occurs. It is even possible that most AN's swell, and most patients have no symptoms. It is certainly true that swelling in a small AN is probably harmless, and perhaps undetectable. A tumor would have to fairly large before swelling, if it occured, would be a risk to health. The two stories I've heard of life-threatening swelling were with medium and large tumors.

Another risk with larger tumors is what I call "overspray." (There's probably a technical name for "overspray" but I haven't seen it yet.)  The principle behind stereotactic radiotherapy is that multiple beams of low-level radiation intersect at an "isocenter" where the combined radiation level is very high. Alternatively, a moving radiation source directs a single beam that swings in an arc around the tumor, with the tumor always in the focus of the radiation beam, and the healthy tissues being only momentarily in the radiation path.

Either way, the tissues near the tumor get more radiation that the tissues far from the tumor due to overspray. The individual beams or portions of the arc must by definition also intersect within healthy tissue. The picture below shows the overspray of irradiating a small tumor.

Click for a larger image.

When a tumor is larger, the beams overlap more, and expose more of the brain to an overspray of radiation.

Click for a larger image.

For clarity, there is an omission in these illustrations:  Since the beam passes through the tumor, the overspray actually occurs on BOTH sides of the tumor.  (except for Proton Beam)

To be fair, there is little evidence that this overspray causes measureable damage to the brain, although it is known to affect the nerves. There are some reports that the rate of trigeminal neuropathy increases with FSR treatment of larger tumors, perhaps because the large trigeminal nerve is exposed to more radiation with larger tumors because of overspray.

update:  I stumbled across a statement that one radiosurgical center (sorry, didn't write down which one) is now using multiple isocenters to reduce "overspray."  Essentially, they treat the tumor as if it were several small tumors.  This is not as much advantage as you'd expect, because the beams still overlap, but it can't hurt.

People - the location of the tumor isn't known to an accuracy that good! You have to add the measurement error of the MRI to the aiming error of the radiation source when determining the combined accuracy of FSR. Frankly, your radiosurgeon would be lucky to aim with an accuracy of 6mm.

The nerves the radiosurgeon is trying to miss are only 1mm in diameter. The accuracy of the radiation treatment is NOT what is preserving your nerves. The nerves are getting most if not all the radiation dose as your tumors gets. The radiosurgeon is counting on the radiobiology of the tumor cells making them more vulnerable to the radiation dose than the nerve cells.

Acoustic neuroma arises from schwann cells which normally serve to protect nerves by growing myelin sheathes to insulate the nerves. In other words, a good portion of the nerves themselves are made from the same stuff as the tumor.

Since these tumors grow slowly, they are only slightly more vulnerable to radiation than the surrounding tissue. This is part of the idea behind FSR. By spreading the radiation out over a week or two, the radiosurgeon has a better chance of catching the tumor cells in the act of dividing.

But this masks one of the confusing facts about radiosurgery for AN. Radiotherapy kills rapidly dividing cancer cells very effectively. Lab studies show that AN radiotherapy does not kill necessarily AN tumor cells, but it still somehow stops the growth of the tumor in most cases. Laboratory studies have exposed AN tumor cells to as much as 150 gy, 6 times the maximum radiation dose which would be used clinically, and the cells survive and grow.

It is a myth that radiosurgery kills the tumor.  Radiosurgery kills some of the cells, but most papers I've read report the primary effect of radiation is that it damages the blood vessels feeding the tumor, and this decrease in vascularity starves the tumor for blood.  With the older, higher dose radiation techniques, this generally stopped tumor growth almost as well as surgery.  Short-term studies with the newer radiation techniques suggest it may have similar rates of growth control with fewer side-effects.  Radiosurgical patients have to be comfortable with the fact that the tumor is still a living part of their bodies, just a part that is no longer growing in most patients.

Of course it is also a myth that surgery kills the tumor.  Surgery leaves behind tens of thousands of viable tumor cells, just as radiosurgery leaves behind millions.  And the tumor started from a single mutated cell long in the patient's past.  The body will kill many of the displaced tumor cells after surgery, once they're out their protective capsule, but some will definitely survive and possibly grow.  Microsurgical patients ALSO have to be comfortable with the fact that the tumor is still a living part of their bodies, just a part that been dramatically reduced in size, (commonly microscopic) and which is no longer growing in most patients.

As mentioned above, two top radiosurgical hospitals reportedly do not consider any patient who drops out of radiotherapy due to complications as a failure, even if the compications are life-threatening. Their argument is that if the patient had only continued the treatment, they would have gotten better.

Another form of failure is when the tumor continues to grow, or resumes growth years later. Generally, this is the definition of failure most radiosurgeons use.

Another form of failure is when the symptoms worsen with no detectable growth of the tumor. Some of these patients elect to have surgery later, and are apparently not reported as failures in some radiosurgical reports because the radiosurgeon views this surgery as unnecessary.

I discovered yet another form of failure at one microsurgeon's office: There are patients who just can no longer deal with having a brain tumor in their head, despite no worsening of symptoms or growth of the tumor. One audiologist told me as many as 10% of their AN surgery patients fell into this category.  These people have a real and serious problem which is psychological, not biological, and they probably represent a small group of patients who shouldn't have had radiosurgery in the first place.

Dr. Mangham removed Kathi Goertzen's meningioma and used radiation to control the tiny bit that was unremovable.  In this case, the surgeon is irradiating a small area, which decreases the risk, as noted above.

If a microsurgeon has to perform salvage surgery after radiation, he will be removing a large lump.  Since the risk for either method increases with tumor size, salvage surgery after radiosurgery is inherently more risky than radiosurgical salvage or cleanup after microsurgery.

The internet gives anyone the power to publish anything, instantly, to the whole world. There are a few patients who have used the internet to transmit an extremely pro-radiosurgery view of AN treatment. Despite their bias, I'll list the best one here with a few comments on its contents because it contains so much valuable information.
 

My criticisms of AN Archive are as follows:

These folks repeat the apples and oranges arguments for long-term effectiveness shown above. When referring to past problems with radiotherapy, these are dismissed because GK is inferior to FSR, but when long-term tumor control is discussed, the data all comes from GK because there isn't any long-term data (and precious little short-term data) for FSR.  Despite studies showing that FSR is superior to single-shot GK, but single-shot GK is inferior to microsurgery, this website is also a hard-core promoter of single-shot GK.

When referring to surgery, these folks provide nothing but horror stories, most of them very misleading.  One poor fellow got hydrocephalus after surgery which caused brain damage which lowered his IQ.  AN Archive then repeatedly states the purported "fact" that surgery lowers your IQ.  Truthfully, hydrocephalus is a vastly more common complication of radiosurgery than microsurgery, so the same patient's story could just as easily be twisted to claim "radiation lowers your IQ."  Either way, this patient's story is irrelevant because a competent microsurgeon or radiosurgeon would have easily prevented his problems.

AN Archive prints horrible results for surgery using data from Podunk University, but success rates for radiosurgery are taken from top centers around the country.  (You're NOT going to let Podunk University treat you, so ignore it.)  CSF leak, which is a minor, temporary annoyance for 10-15% of microsurgical patients is reported as a horrible thing to fear.  BY comparison, hydrocephalus, a potentially life-threatening condition which occurs in 8-10% of radiosurgical patients (and which hardly ever occurs in surgery) is barely mentioned.  Hydrocephalus is much more difficult to treat than CSF leak, requiring the installation of a CSF shunt under general anethesia.  Ignore BOTH of these complications when making your choice, because neither one is an issue with competent care.

A last complaint is that fragments of patient's stories are presented without quotes or bullets to separate them.  This sometimes makes it look like a patient's opinion is part of the editor's factual statements, or makes it look like multiple complaints about complications all occurred to one terribly unfortunate microsurgery patient.

Regardless, the AN Archive contains lots of valuable information for surgical patients, if you can get past the bias.  They have good information about vestibular rehabilitation exercises I've never seen anywhere else on the web.

And I strongly agree with one of the AN Archive's recommendations: ALL newly diagnosed AN patients should be referred to BOTH a radiosurgeon and a microsurgeon.  The medical community still hasn't acheived a concensus on treatment for AN, and when disagreement on treatment exists, health care providers are obligated to expose patients to all the options.

There is another hard-core patient advocate of radiosurgery whose site I've chosen not to link here.  This advocate went to the same quiet, introverted, microsurgeon I visited, and calls him "arrogant" for making a widely accepted recommendation for conservative treatment for her small AN.  Since a chosing treatment for AN is a matter of chosing which particular poison you find least offensive, I think some patients rail against medicine for not being able to cure them perfectly and painlessly.

I am hesitant to condemn the ANA, but please remember that this organization was formed in the past as a post-surgical support group, back when treatment was far less successful that it generally is today. Today, the ANA’s relevance has slipped somewhat.

Today, the ANA seems to function mostly as a home for patients whose neuromas who received the less-effective treatments of the past, patients whose neuromas weren’t discovered until they had reached life-threatening sizes, or those who received botched treatments. The membership seems to be made up almost entirely of people with unhappy outcomes – this is not a place to go to find unbiased information about treatment.

I think there's a natural bias on the internet about AN.  AN microsurgical patients with positive outcomes no longer consider themselves AN patients.  They never join the "AN Survivor Community."  They move on with their lives and never bother to post their experiences on the internet.  This is certainly the experience of the few patients I've met.  Microsurgical patients with poor outcomes are looking for support and someone to comiserate with, so they join the ANA and/or post their horror stories on the internet.  (see also UK comment below)

By contrast, radiosurgical patients have to have periodic MRI's to verify the tumor is not growing.  Even those with the best outcomes never stop being "AN patients."  They join the "AN Survivor Community" and post their stories online. This is at least one reason why we hear lots of stories of positive outcomes for radiation.

When the radiation therapy (especially GK) has long-term complications like delayed cochlear, facial, or trigeminal nerve damage, the onset of nerve damage occurs over the course of months or even years, rather than the abrupt failure which occurs when surgery goes awry.  The slow onset of complications does not motivate patients to report their horror stories, as they have had a long time to get used to their conditions.  This may be one reason we don't hear from the GK patients with poor outcomes, despite the statistics showing there must be thousands of them.

Lastly, some patients had to fight to get their treatment covered by their insurers - some of these patients become crusaders, promoting the cause.

Microsurgery for AN is like cutting into the side of your house with a chainsaw to get at frozen pipes, while hoping you don't cut into the house wiring. Radiotherapy is like playing a blowtorch over the outside wall to thaw the pipes, and hoping you don't start a smoldering fire that could erupt hours later.  Techniques have GOT to improve.

In the near future, AN might be treated with focused ultrasound. This technique is similar to, and gives all the advantages of radiotherapy, but since the treatment is only induced heat, not radiation, some of the long-term side effects (delayed nerve damage, for example) should be eliminated.  Like radiosurgery, the tumor is inactivated, but not killed or removed.  Stereotactic microwaves (just like your oven!) might also offer the same advantages.

Both benign and malignant tumors emit chemicals that ask the body to route them more blood vessel as the tumor grows.  This is called angiogenisis.  Radiosurgery or ultrasound might be enhanced with recently developed drugs that inhibit angiogenisis.  You fry the tumor's blood vessels with a very low dose of radiation, and the drugs prevent the blood vessels from healing or growing back.

Farther in the future, perhaps 10 or 20 years, some biotech company will make a vaccine that teaches the body's immune system to attack the mutated schwann cells in the tumor. Or perhaps a biotoxin will be used to deliver poison directly to the mutated cells. Or perhaps DNA therapy will be used to correct the mutated DNA in the tumor - when the damaged tumor preventer gene in the neuroma cells is repaired, the tumor cells should commit suicide.

These biological techniques will be the real "better than sliced bread" treatments, the undeniable holy grail for AN. The tumor will be dissolved slowly, and absorbed by the body. The slow removal of the tumor will preserve the cranial nerves like radiotherapy, but the tumor will be eliminated like surgery. Within our lifetimes, the debate over microsurgery vs. radiotherapy will be void.  Unfortunately, those of us diagnosed today (2000) can't wait for these holy grail treatments to arrive.

There appears to be a special difficulty in the UK, where most people use a government health plan and apparently have little choice but to have their surgery performed by the local neurosurgeon, who may perform two or three AN removals a year.  Given the awful choice between an inexperienced microsurgeon and an inexperienced radiosurgeon, choose the inexperienced radiosurgeon every time - I've had several otologists tell me the level of skill and experience required for acceptable outcomes is lower with radiation.

Alternatively, do what one patient I know did - pay for the best treatment with your own money.  It's worth it.