This is long. Sorry. It kinda has to be in order for you to understand the results of today's visit. Let me tell you a story...
***Part 1: Background***
Many of you will remember that in early August 2004, approximately four years ago, Martin collapsed at work with stroke-like symptoms. When he was taken to Sunnybrook Hospital (I know that's not technically its name), it was discovered that he had 2 AVMs in his brain, and that one of them had ruptured, sort of like an aneurysm. (If you don't know or don't remember what an AVM is, don't worry, I will include info on that below.) The focus four years ago was on saving Martin's life as the bleeding AVM threatened his life, then on getting him conscious again, then on getting him back to full mobility and so on. The AVM that had bled was removed via surgery two days after he collapsed (yes, Martin has had brain surgery), but since the other AVM was in a different area of the brain they did not traumatize Martin's brain further by digging around for it at that time. AVM #2 was left alone for the time being.
Three years ago, the medical team was pretty much satisfied that Martin had recovered enough from his bleed that they could start treating the other AVM--i.e., to do preventative work on it to get it to a point where it would not be able to bleed like the other one had. (Untreated, there is a 3% chance *every year* that an AVM can bleed.) The treatment recommended by the team was a highly focused type of radiation, which could be used to target just the AVM while leaving the surrounding brain tissue unaffected. Treating an AVM with radiation is not like treating cancer with radiation, however; while cancer patients go in for multiple bursts of radiation over many days, an AVM patient spends only about 20 minutes being treated in the radiation room (well, once all the setup is done...it takes a full day of CAT scans and such to prepare for it), receiving only 2 short bursts of radiation during that time. The radiation is completed on a single day. (The reason multiple sessions aren't required for an AVM like they are for cancer is because cancer grows...an AVM does not. As Schwarzenegger would say, "It's not a tumour.")
One day of radiation...that's all it takes. However, the treatment does not actually stop there. The purpose of the radiation is to create scar tissue inside the blood vessels of the AVM--scar tissue that builds up and builds up slowly, over the course of three years or so, until the AVM's blood vessels finally clog up and stop allowing blood to flow through them. If no blood can get into the AVM, the AVM can't bleed. While it might sound like a bad thing to cut off blood circulation, this is actually safe (and desirable) with AVMs because the blood vessels in an AVM do not service any part of the brain...they're kind of a tangle of useless blood vessels (more on this below). After the day the radiation is received, the patient goes about his daily life as usual, not coming back to the hospital until 2 years later (when the medical team looks to see if the radiation has done its job and finished making enough scar tissue), and, if necessary, once a year every year after that until the AVM shows that it has been fully treated. No additional radiation is given at the 2- and 3-year checkup (unless, I guess, if the progress of the AVM's treatment has been unsatisfactory and the medical team recommends it).
Last year, in the summer of 2007, the AVM clinic had Martin get an MRI done, and when the results came in we went back to the clinic to find out how the treatment of his AVM was progressing. The doctor told us last year that the MRI showed the AVM was either gone or almost gone, but that the resolution of an MRI is not fine enough to tell us for sure if it was indeed fully gone. For that, you need to get an angiogram done--a very invasive and uncomfortable procedure. The medical team recommended we wait another year, get an angiogram done at the end of that year, and then come in when the angiogram results were read to see what they had to say.
Today was the day of that visit.
***Part 2: A refresher on what AVMs are, and the results of today's visit***
The first picture above shows very loosely what an AVM is. On the left is an artery--a blood vessel that carries blood away from the heart, designed to handle the high pressure that such blood is under. On the right is a vein--a blood vessel that carries blood towards the heart, designed only to handle the much lower pressure that such blood is under. Normally, blood flows from an artery through several tiny blood vessels called capillaries before it gets into a vein, and the capillaries reduce the pressure the blood is under. In an AVM, these capillaries just aren't there. The vein shows up early, so to speak, and the blood flows directly from the artery into the vein. Because the vein is not designed to handle the kind of pressure the blood from the artery is under, there is a risk that it will rupture, causing bleeding into whatever body part the AVM is in (which, in Martin's case, is the brain, and bleeding in the brain puts pressure on the brain and is A Bad Thing). In addition to this direct artery-vein connection, this set of blood vessels is malformed, making a kind of tangle or knot of blood vessels in the brain. Hence the name AVM, which is short for arteriovenous malformation--"malformation" because of the tangled knottedness of it, "arteriovenous" because it involves an artery and a vein.
As I said before, it's not a tumour. It is not cancer. It does not grow. You do not develop it later in life. If you have one (or more than one!), you are born with it, and you would never know it until either it ruptures (this is how we found out about Martin's...collapsing with stroke-like symptoms kind of calls attention to something being wrong) or you require an MRI for some reason on the part of your body that happens to have an AVM (this is how we found out Martin had a second AVM and not just the one that burst). Even having a CAT scan for something else in your life generally will not call attention to any AVM you might have, because the resolution of a CAT scan is not fine enough to point them out. A more realistic picture of an AVM can be seen at http://brainavm.oci.utoronto.ca/images/malformations/avm_embo_treatment/what_is_avm.jpg.
Alright, enough background and on to the results. Three years ago, the medical team told us the AVM was approximately 2.5 centimeters in diameter (that's about an inch, for you non-metric folk). Today, we were told that it seems all that is left of the AVM is a shunt, although it is possible there may still be a small amount of tangle there. When I asked what size it is now, the doctor said it doesn't really have a size anymore, and that is when she drew the two diagrams that I have attempted to reproduce here. The second picture above shows what Martin's situation is now. The blood is still going directly from an artery to a vein (which is a Bad Thing), but most if not all of the tangle has been dealt with. The radiation has almost completely dealt with the AVM. Because the blood is still going directly from an artery to a vein, there is still a possibility of a bleed occuring. The doctor who spoke to us told us the chances of a bleed might be lower with this situation than what the chances were 3 years ago, but that there aren't enough good studies out there right now for the medical team to know for sure.
Where do we go from here? The medical team recommends we wait 1 more year and get another angiogram done at the end of that year, then come back to the AVM clinic when the results of the angiogram are ready to see what they have to say. Hopefully we will discover that the radiation has finished its job and closed off even this shunt. If not, we will have to make a decision: do we do another burst of radiation, or do we leave the AVM as-is and live with the (maybe reduced, maybe not) risk that it will bleed at some future point in Martin's life? Well, that is a decision for next year. For now, I will be glad that the AVM is much reduced from what it used to be, and hope that when we go back next year we'll find that the AVM is completely gone and that no further treatment is necessary. More radiation would not be the end of the world (especially since it was so effective in reducing the AVM down as much as it has), but it would mean quite a bit of discomfort for Martin on radiation day and for a few days afterwards.
There, I think I've said all I wanted to get out. Feel free to ask questions if you need clarification on anything above or just want to "know stuff."
