Hi Kippy,
My AN is going through necrosis following Cyberknife treatment last summer. I've been having follow-up MRI's with a local neurosurgery practice and after the last one they told me that I may have necrosis in the area outside the tumor as well. I had new hyperintensity - bright spots on the "T2" series of my MRI - in the area surrounding the tumor that they thought might indicate necrosis. I was referred to a new radiation oncologist who agrees with my CK doc that there is necrosis inside the tumor, but no necrosis outside the tumor. They didn't tell me exactly what the new spots on the MRI are caused by, only that it should be temporary.
To be honest, I'm not real thrilled at having a decaying tumor wedged up against my brain, but the radiation docs don't seem to think it's a problem. Right now, all the dark stuff in the AN is still inside its "capsule", so I don't think there's any concern. Not sure what will happen later on, but the docs tells me the body's natural "clean-up" processes will take care of it. Sounds good to me.