Saturday, January 10, 2009
If a Tree Falls in the Forest...
Kim, at Sunshine and Moonlight posed the question: What happens to lesions when they've disappeared? So I asked the question to Mike, one of the neuro nurses at the MS clinic here in Halifax. The short answer is that they don't disappear, they just stop being active. Because they aren't actively inflamed, they don't show up on the MRI.
Now for the long answer.
Remember, MRI measures water content and water is composed of hydrogen and oxygen. First the MRI machine produces magnetic fields (causing all the hydrogen protons to line up in a certain pattern), then a radiofrequency electromagnetic field is applied. Energy from that second field is picked up by the hydrogen protons, and when the second field is stopped the protons release energy at a radiofrequency that can be detected by the machine. The position of the protons is what is measured. And we get pretty pictures of our insides.
When the protons release energy, they do so at a certain rate. Diseased tissue releases energy at a different rate than normal tissue and this is what is detected by the MRI machine and accounts for us being able to "see" lesions.
So, if a lesion is not detected, does it mean that it's not there? Here we get to that whole tree-falling-in-the-forest thing. An active lesion is one that is inflamed. Now we need an explanation of inflammation.
Inflammation involves the destruction of myelin. Just as when we have an injury to our skin, a number of processes occur. Chemicals and cells rush to the scene to detect "bad" cells and try to eliminate them; at the same time, "good" cells are trying to repair any damage. All this activity is what causes inflammation on our skin and it's much the same in our brains. Inflammation is the process of the body identifying the "bad" cells, eliminating them, then attempting to repair the damage. And if a cell dies in this process it is eaten up and eliminated as well.
All of this activity goes on for days, weeks, and even months before we are even aware we have MS or before we exhibit symptoms. Some lesions may have resulted in permanent injury to the axons of some nerves, what they call axonal degeneration. Shrinking of the brain, called brain atrophy, can occur. Remember, dead tissue is eaten up and eliminated by the body, and in the case of our brains, unlike our skin, it is not regenerated. So we end up with "neurodegeneration" and shrinking of our brain. Scar tissue remains, but there is no activity in it. So the MRI machines can't measure it. The lesion may be gone (when looking at an MRI picture), but the results of its previous activity remain.
So the short answer to "Where do the lesions go?" is nowhere. The scarring remains, damage may be permanent, but there's no activity in that spot of the CNS. At least, none that we are capable of measuring at this point in time.
I hope that answers the question. My concern is with people's "fixation" on lesion counts.
So why do we seem to be so fixated on lesion counts? Because right now, that's all we have to grab on to. That's all we have to physically look at and point to to explain symptoms. By the time we exhibit symptoms, the disease process has already been under way for some time and there's little we can do to repair the damage.
Sounds kind of grim, doesn't it? We know this process is going on continuously, so until we can stop MS, we do what we can to slow down the process of axonal degeneration and brain atrophy. Most of us get a course of steroid treatment in the early stages. The steroids quite often stop inflammation in its tracks, which is why we see such marked improvement with steroids alone (sadly, the risks of continued steroid treatment are too great for it to be used often). OK, so we stop inflammation, now what? You are given a choice of one of many disease modifying drugs. These drugs reduce the number of attacks and their frequency so you will go longer without disability. And that's all we can do right now.
Each attack results in inflammation, which can result in permanent damage and atrophy, so logically, we should try to reduce the number and frequency of attacks. While we are doing that by taking a disease modifying drug, we need to be doing other things to aid our bodies in the repair process. Exercise, eating right, getting enough sleep and rest, and reducing our "bad" stress levels are all things that we can do without expensive drug regimes. Exercise your brain, too, learn different things, or attempt them. It's the attempt that exercises your brain.