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Gamma Knife Radiosurgery Archive Questions

Below are Dr. Kwok’s answers to Gamma Knife Radiosurgery questions
received through the Ask the Expert feature.

This content is provided for informational purposes only, and is not intended
to be a substitute for individual medical advice in diagnosing or treating a
health problem. Please consult with your physician about your specific health
care concerns.

Now displaying records 1 to 15 of 57.

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Q : 1

Can Gamma Knife be used for brain stem glioma in children?

For a diffusely infiltrative glioma, the answer is no. For a small, focal brain stem glioma, it is possible.

Q : 2

My mom is 87, has trigeminal neuralgia and has had Gamma Knife treatments done twice. The last treatnent was four years ago, but now the pain is back in same area of her jaw. Can she have this treatment done again? Could there be side effects?

She can get it the third time. The more you do it, the higher the chance of facial numbness, which is not necessarily a bad thing.

Q : 3

Why does the tumor have to be less than 4cm for gamma knife surgery?

The upper limit of 4cm comes from the fact that at that size, the toxicity rate goes up significantly and the control rate goes down significantly. No matter how accurate radiosurgery is with gamma knife, you still have a thin rim of normal tissue that gets included in the high dose region. The definitive paper was RTOG 90-05 by Shaw in 2000. The modeling of toxicity rate, size and dose was done by John Flickinger in Principles and Practice of Radiation Oncology, 5th edition page 382.

Q : 4

Can Gamma Knife be used for large benign tumors?

It all depends on how large and whether it is on the optic chiasm/nerve. When we speak about "large," we are typically referring to more than 4 centimeters. Also, the tumor cannot be within couple of millimeters to the optic chiasm/nerve since the gamma knife itself can cause blindness.

Q : 5

I understand that there is a trial going on at the brain tumor center that is showing promising results for brain tumors. Where can I find more information?

There are many trials being performed throughout the United States. One very helpful resource is:

Q : 6

Will Gama Knife surgery actually reduce the size of the tumor or just stop it from growing?

This depends on the type of tumor. A vast majority of metastatic brain tumors will shrink significantly. For malignant primary tumors, it may or may not shrink. Benign tumors are very unpredictable. A significant amount will shrink, but will do so very slowly, over many years.

Q : 7

I have relative that was diagnosed with a meningioma. She had surgery, but the doctor was only able to remove about 80 percent of the tumor and suggested follow-up with Gamma Knife surgery. After her initial surgery, she began experiencing facial paralysis. Her left eye can't close, she can't speak clearly and she can't hear out of her left ear. How long does she need to wait to have Gamma Knife? Will she get worse?

I wouldn't consider surgery until her cranial nerves, especially the facial nerve, start improving. It's not unusual to wait one year or so after surgery before attempting Gamma Knife. If the Gamma Knife is done too quickly after surgery, the nerves will never improve.

Q : 8

I have a grade 2 oligoastrocytoma. I have had several operations over 15 years, but the tumor is growing again and my blood supply is poor. Would the Gamma Knife operation be possible given the new growth? Would chemo be possible? What type of chemo would be best from your experience?

If you've never had fractionated, external radiation (daily radiation), then most people would consider that to be the standard. It's typical over a course of 6 weeks or so. If you've had radiation and again with the tumor regrowth, then surgery should be performed by an experienced surgeon. After that, Gamma Knife (or other technologies that can do stereotactic radiosurgery) can be used if there was a piece of tumor that could not be excised. You need to be evaluated by an experienced medical oncologist for consideration of chemotherapy. Most would give you chemotherapy after a repeat surgery, and the most common chemotherapy agent in this setting is Temozolomide.

Q : 9

I'm 53 and was diagnosed with a meningioma at the right side of the brain, found on an MRI test. It's the size of a small marble. I constantly have cramping in my whole body, especially on my right side including pressure on my right eye. Would it be better to get Gamma Knife radiosurgery or another treatment?

It is very unlikely that right side of the body is affected by a right sided tumor. The pressure over the right eye may or may not be related although still unlikely. I would get a consult from an experienced radiation oncologist. If the physician thinks that the symptoms aren't related, then the gamma knife is very reasonable option with ultimate control rates being greater than 90 percent. In terms of ultimate local control, gamma knife is as good as anything with very little risk of complication. Surgery does have an advantage with tumors that are causing significant neurological symptoms since the tumor after gamma knife shrink very slowly.

Q : 10

I had Gamma Knife about two months ago. The MRI lab tech said that my brain tumor was a schwanomma. But I met with 4 different Neurosurgeons who indicated that they believed the tumor was a meningioma- particularly since I was asymptomatic. On the day of treatment, I was treated with the GK for a trigeminal neuralgia. All of this has left me quite confused. My biggest concern is whether the tumor will be induced if I get pregnant especially since the doctors still suspect that I have a meningioma. Does it really matter?

In the base of skull, sometimes it is very difficult to know whether a tumor is a schwanomma or a meningioma, both of which are benign. Both can cause a secondary trigeminal neuralgia (pain involving the face from trigeminal nerve distribution) which is caused by the pressure from the tumor. To treat the facial pain, you have to treat the tumor. Whether it is a schwanomma or a meningioma, it should not deter you from having kids. Yes, pregnancy can cause a meningioma to get bigger on rare occasions but you will be under the care of brain tumor specialist who would know this. There is no need for a biopsy because it is very dangerous and wouldn't really change anything.

Q : 11

Can the gamma knife procedure be repeated to treat trigeminal neuralga?

Yes. While I cannot attest to other centers' comfort level with repeat gamma knife procedure for trigeminal neuralgia, it is routinely performed at our institution. We have published our data as have many other centers.

Q : 12

Is Gamma Knife treatment effective for removing hemangioblastoma? What are the chances of recurrance? How long is the treatemt?

Yes, Gamma Knife has been used quite effectively to treat hemangioblastoma, provided that it is not too large or in close proximity to sensitive areas like the optic nerve or the chiasm. There is only a recurrence rate of about 10%, indicating that Gamma Knife is a very good treatment. Good luck!

Q : 13

Are pituitary tumors hereditary? My Dad had one and now his brother has been diagnosed.

It can be, in rare cases, as part of multiple endocrine neoplasia (MEN) syndromes.

Q : 14

I was just diagnosed with a subependymoma tumor in the 4th ventricle of the brain. It is less than 1 cm in size. Could this be treated using Gamma Knife? My only symptoms thus far are a slight leg tremor and lower vocal strength. Could this tumor be causing these?

Typically, we only reserve Radiosurgery (like Gamma Knife) if a subependymoma is causing problems (which may be in your case, depending on the location) and it cannot be removed with surgery. We try to avoid radiation for benign tumors unless surgery is too dangerous.You should be evaluated by an experienced neurosurgeon for consideration for surgery.

Q : 15

Can the Gamma Knife be used to treat shoulder bone tumors which have previously undergone radiation treatment? And, can the Gamma Knife be used to treat pancreas tumors?

Gamma Knife is a stereotactic radiosurgery tool for the brain and upper cervical spine. There are a variety of other stereotactic solutions available that can treat the body. For brain tumors, nothing is better than the Gamma Knife. That's why you frequency see large academic hospitals have different stereotactic machines for different situations. So, there are plenty of stereotactic solutions (e.g., cyberknife, trilogy, brainlab, etc.) for the shoulder and the pancreas.

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