Advances in the Treatment of Spinal Muscular Atrophy - Episode 6
Crystal Proud, MD: We've talked a lot about symptoms of SMA [spinal muscular atrophy], diagnostic tools, and assessment tools. We've talked about implementation of newborn screening, and without newborn screening, do we see a significant time between symptom onset and referral time to a pediatric neurologist? I was hoping to ask Nancy her thoughts on this.
Nancy L. Kuntz, MD: I think that there really has been, over time, quite a bit of delay from the parents’ point of view. When people have gone back in the family support groups and looked at the time at which the parents first become concerned, the time at which they first raise questions to the pediatricians or primary care doctors, and then the time of diagnosis, there appears to be a variable but very significant lag of many months. I think that there are many reasons for this.
Part of this is that there is variability in individual development of babies, so that every baby doesn't sit exactly at 6 months. Every baby doesn't walk exactly at 12 months; you know I’ve seen it from 8 months to 15 months, for example, with walking. With each of those little milestones, with head control or rolling or others, it can sometimes be difficult to know whether a child is just taking their own time or whether in fact, they are delayed.
I think it's a very compassionate part of many primary care physicians who deal with children who want to give them the benefit of the doubt. Unfortunately, in this circumstance, giving them the benefit of the doubt an additional number of weeks or months to manifest some improvements in development can lose some incredibly important time for treatment here. The other thing is that one of the terms that's usually used to describe children with symptomatic infantile SMA is hypotonia, without pediatricians really being sure whether it's just low tone, or low tone and weakness.
Certainly if you look at the broader group of things that cause low muscle tone in children, particularly infants, problems with the brain or central problems are much more frequent than peripheral neuromotor, motor unit problems. Then SMA is only a small fraction of that. I've seen children where people want to be very thorough, and they start off with CT [computed tomography] head scans or MRI [magnetic resonance imaging] head scans, and chromosomal microarrays and metabolic testing, which given the entire universe of all the things that could cause hypotonia in children, are probably more frequent than spinal muscular atrophy, but most of those aren’t treatable.
I really think that as we move into an era where there is much more available in terms of treatment of specific rare disorders that our emergent response to seeing these children really should be to look quickly for the potentially treatable things, and start with the things that are most likely. Certainly if there is that diminished reflexes, or the tongue fasciculation, or other things, consider going straight to the spinal muscular atrophy gene test, not waiting to schedule an EMG [electromyography] weeks or months out. I think this is going to be a complete paradigm shift in terms of response to children who present.
Crystal Proud, MD: I agree, it's been a shift in perspective. And I know that locally, when I've been speaking as a child neurologist to the general pediatricians in the area, reassuring them that they can reach out to me in the event that they have any concerns about motor delay, I think that their primary concern is that they will then inundate my office with these referrals. I say to them in response that I'd rather see a child and reassure them, do the testing, even if it comes back to be negative, than miss an opportunity to diagnose and treat early. I think all of us would agree with that.
Julie Parsons, MD: I would agree with that, too, Crystal, and I think that there has been a pervasive thought because SMA is a rare disease; we all take care of patients with SMA. But in a primary care provider's practice, they might see 1 patient with SMA during their entire career. It's not something at the forefront of their mind. I think that really spreading education and the word that we do have treatments available.
It's very important to make the diagnosis early now, and I do think that primary care providers are getting that message now. It's our duty to continue to provide the education to them, as well as to have them understand, as you said, that it's not going to be a 6-month wait to get in to see neurology, that we consider this an emergency now, just as we would a stroke in another patient, so that we can treat patients urgently.
Crystal Proud, MD: Absolutely.