Current Series: Understanding Spinal Muscular Atrophy

Nancy L. Kuntz, MD: Part of that multidisciplinary team really is the basic primary care clinicians who follow the children with all the complex things that go into that. One of the other areas that is very critical, other than just primary care, would be caring for ventilation and pulmonology things. What kind of experience have you had at your center with pulling in the pulmonary people with that aspect?

Claudia A. Chiriboga, MD, MPH: Well, many multidisciplinary care clinics have pulmonary physicians included, and our site has a pulmonologist who’s experienced in SMA [spinal muscular atrophy]. I think that what I’ve discovered from having patients from across the nation for clinical trials is that there is a wide variety of practices across the nation in terms of how readily available BiPAP [bilevel positive airway pressure] machines are. Can you use it preventively? Do you have to do sleep studies to obtain that?

At our site [Columbia University Medical Center], and I think many sites in the Northeast, preventive BiPAP when the baby is weak, fatigued, or having failure to thrive is the norm without requiring sleep studies to be done in these little infants. Before we even go there, cough assist is mandatory to have, especially in the early infant onset and in some of the weaker type 2 patients, later infant onset, especially when they have intercurrent infections because they may not need it when they’re healthy. But the moment they have a respiratory infection, then they can get into trouble. So having that equipment available before they have trouble is very important.

Nancy L. Kuntz, MD: I can recall, and it wasn’t so long ago, that this was a little bit of a leap of faith to do the insufflation, exsufflation. In the very tiny babies, the concern was whether their lungs could stand up to the pressure of doing that, but obviously it’s made an incredible difference.

Claudia A. Chiriboga, MD, MPH: It certainly has, and the experience is that when you look at the orthopedic deformities that come from the parasol deformities because they have that diaphragmatic paradoxical breathing and narrowing of the upper thorax, that prevents proper ventilation. So having BiPAP at night allows expansion, prevents atelectasis, and helps them have less labored breathing, so that they don’t spend so much energy trying to capture breath. And I think that’s made a huge difference, and I think the natural history data show that just having BiPAP support really improved mortality, or survival rather—because otherwise, without that respiratory support, the babies were going to not survive past age 2. As they get weaker, obviously then there will be a need for chronic respiratory support 24-7. And in some places, a tracheostomy may be needed. Though we try to avoid it as much as possible.

Nancy L. Kuntz, MD: One of the things I think that we sometimes forget about when we’re thinking about respiration, pulmonary care, and support is just transport of the children. Babies with SMA tend to fail the car seat test, and once you’ve thought about it a bit, it makes sense. But it isn’t something that everybody recognizes right at the beginning. Why do you put your babies with SMA in car beds?

Claudia A. Chiriboga, MD, MPH: That’s a very good point, and that has to do mostly with decreased ventilation just from the head dropping forward because of weakness and not being able to have sufficient ventilation as a result of that. And there have been unfortunate incidents where the babies have been placed in a regular car seat, and they arrive at their destination, and the baby’s head drops forward and then they did not survive the trip. So it’s important in the weak child with SMA to have the car beds. Now that we have treatment, there is a false sense of security that some parents have that the children are doing better and that they don’t need to do all these things like carry their cough assist, take their BiPAP with them, or use the flatbed car seat because they’re a bit stronger. And those are babies also that run into trouble, unfortunately.

Nancy L. Kuntz, MD: I’ve always felt, too, that some of the difficulty with those incredible bucket car seats for infants is that it flexes the baby so much and seems to really push a lot of abdominal contents right into the diaphragm. As we all have seen, the babies with SMA tend to use their diaphragm much more for breathing than the intercostal muscles. And I think that’s another complicating feature as well. And so clearly, the rule of thumb for natural history is that without treatment from the time of diagnosis, these problems only seem to increase slowly and condition worsen. The nice thing in this generation is that hopefully that natural history will change, and so whether we can discard the car bed and go back to the awful bucket car seat—which is more convenient for small cars, I know—we’ll have to wait and see, I think.