Many of you have heard terrifying reports of a scary outbreak of an illness called Acute Flaccid Myelitis, or AFM. To explain the name, acute means it happens suddenly, flaccid means your muscles go limp which is a way of saying paralyzed, and myelitis means inflammation of the spinal cord.
AFM is said to be not new, but recent attention to this disease took off after a new outbreak occurred in 2014, in Denver.
The first thing to say about AFM is that it is rare. Even if you add up all the cases known to have happened in the United States, the chance of a child coming down with it remains no more than 1 in a million. That is extremely rare. That is equal to the chance of being hit by lightning. It does happen, but once you get to 1 in a million levels of risk, you still go about your daily routine without much worry. People do get hit by lightning, but at 1 in a million, the chance so remote, we still go walks outside without much worry.
The Key Signs Symptoms that Establish the Diagnosis of AFM
These three facts must be present to have the diagnosis of AFM, miss even one of them and you don’t have it:
- You have to be under 21 years old. All sorts of odd neurologic events occur in adulthood that could explain the other 2 findings, so you have to be under 21 to say it’s AFM.
- You have to have some muscle failure- in the form of weakness, droop, or inability to move. That can happen in the muscles of the eyes, face, neck, back, or limbs, but typically the limbs. No muscle weakness or paralysis, no AFM.
- Most if not all cases show abnormalities on MRI in the spinal cord, not so much the brain, just the spinal cord.
AFM strikes mostly young children, the average age of the 368 or so cases so far has been 4 years old.
Many but not all experience pain.
The muscle weakness and paralysis can be around for a short or long time, and it is impossible at this point to know if your case will be long or short.
Even worse, there is no therapy or intervention, or treatment that can make the muscle failures go away or be present for a shorter time.
Making Sense of Muscle Weakness from the Spinal Cord
We all have 3 types of muscle,and they each operate under very different rules and controls. There is the heart muscle, smooth muscle, and skeletal muscle.
Heart muscle pumps the heart, and is always active. Smooth muscle makes hollow structures in organs get bigger or smaller, such as the uterus when contractions occur, or the iris in your eye when the pupil gets larger or smaller, and many other organ-related functions.
Skeletal muscles are the only one of the 3 that are under voluntary control to a nearly complete degree. We can influence our heart function and how fast our heart beats, but we completely control if our arm moves. So we know the control of the skeletal muscles must be different than the heart and smooth muscles, and it is.
So, here is how it goes with skeletal muscles. All of them are under direct control of the brain, where much of the cerebral cortex and the inner brain structures are set up to determine which muscles will move, when, to what purpose, and with exactly what balance of forces. This dictates whether we are sitting down reading this posting, playing piano, going to work, driving, eating, or whatever we might want to do.
Skeletal muscles move when the brain completes an approach to movement. The signals to execute that movement go out a nerve from the brain that travels to the spinal cord for all muscles below the neck. The spinal cord is organized into segments, which you can see if you look at the vertebrae of the spine, each are a block with a space between them. That space is where a major spinal nerve exists the spinal cord, and informs the movement of a stripe of muscles defined by the space. So the gap between two vertebrae at the level of the abdomen control all the muscles described by a stripe of the body whose upper boundary is at the top of that space and bottom at the edge of the vertebrae below that space. A more complicated but very similar map determines which nerves from our spinal cord control which muscles of our arm and leg.
The key to AFM lies in the connection between the nerve from the brain signaling what each muscle should do right now (my brain right now is signaling muscles to allow me to type this post), and the nerve that goes out from the spinal cord to the actual muscle. That connection happens at the very front of the spinal cord, up and down all its segments. The long nerve from the brain ends in the front of the spinal cord,and there connects to a nerve called the anterior horn cell. The anterior horn cell is a long nerve cell that goes from the spinal cord, to the muscle. That nerve cell for the muscles of the foot is several feet long, going from spinal cord to the foot.
And now we can come to how AFM happens. For reasons yet unknown, children with AFM have inflammation of their anterior horn cells. Inflame these cells and the muscles they go to cease to function normally. Reduce their function a bit, and the muscles at the end of the nerve get weak. Reduce their function a lot, and theses muscles stop working, they go fully limp, or flaccid, that muscle can not be said to be paralyzed.
Unfortunately, our current understanding of the cause is simple to state: no one knows.
Since we do not know, there are of course theories of cause. Some think it is the result of a virus, some say an environmental toxin, some say it is caused by a genetic issue. But we have no idea as of today.
There are some hints that a virus is at work here:
- Most kids with AFM had a preceding cold.
- Some, but not all, kids with AFM were found to have an interesting virus in their spinal fluid. It is in the genus of viruses called Enterovirus (EV).
Enteroviruses are very familiar to families as they cause most of the stomach flus in the summer, nearly all cases of hand-foot-mouth, and many cases of just very high fevers.
Enteroviruses are also known to cause inflammation around the spinal cord, causing most of the cases of summertime viral (not the dangerous bacterial) meningitis, which is almost always a harmless illness.
The most famous of all enteroviruses was once wildly common, but now on the brink of extinction, it is the polio virus. Most people do not know that if 100 people got infected with the poliovirus, most would have only a stomach flu, only a very few would go on to have spinal inflammation with subsequent weakness and/or paralysis.
Enteroviruses are relevant because the symptoms of AFM look very, very much like polio. Like AFM, people with polio got muscle failure due to inflammation of the anterior horn cells of their spinal cord.
Enteroviruses are also of interest because one strain has been found in nasal swabs, not spinal fluid, in a number of children with AFM, it is enterovirus D68. This has not been established as a cause, because enterovirus D68 can cause large outbreaks of colds. So you can have a community where thousands upon thousands of people get a cold from enterovirus D68, one child gets AFM and has the enterovirus D68 cold before. She may have enterovirus D68 growing in her nose when the AFM hits, but that does not prove a virus, or that virus caused it.
And so, we are left wondering what is causing AFM. This is particularly difficult as it happens in fewer than 1 in a million children.
The good news it that there are few if any groups of people with AFM, it does not appear to be contagious.
At this time, the only treatment is comfort and recovery exercises. Once a cause is found, then possible interventions to prevent AFM, and even treat it, can begin to be explored.
- Once again, a scary medical news story is afoot. It’s about Acute Flaccid Myelitis, AFM, which essentially means sudden onset of muscle weakness or paralysis due to sudden inflammation of the part of the spinal cord where the nerve carrying instructions from the brain to the muscle.
- AFM IS INCREDIBLY RARE. Total cases show it happens to fewer than 1 in a million children. Like lightning, it happens, but so rarely it should not make us change what we do.
- AFM does not appear to be contagious, not patterns of spread have been seen of AFM.
- We know very little about cause or treatment, stay tuned.
We hope no one else comes down with AFM, will keep you up to date on new developments.
To your health,
Dr. Arthur Lavin