Melissa Wright, MD, PhD, discusses common signs and symptoms of SMA, including proximal muscle weakness, changes in gait, falls, tremors, and muscle fasciculations.
What are the signs of SMA muscle weakness?
Transcript
One thing that’s a little bit surprising to many people, because SMA is a nerve disease instead of a muscle disease, is that it often affects the proximal muscles more than the distal muscles, and it tends to affect the legs more than the arms.
Because of this, children and adults will often come in with difficulty with things like getting up from the floor, climbing stairs, changes in their gait pattern, and sometimes with falls.
It’s progressive over time, so they’ll tell you that this has been getting worse over several months or several years. And in a younger population, it’s pretty common to have a more rapid progression of symptoms during puberty.
In the clinic, when you’re seeing a patient who comes in with these complaints, you may find that there’s weakness of the hip girdle muscles, weakness of the quadriceps and hamstrings. In the arms, you’ll probably see weakness in the deltoids and in the triceps.
You may see that they have a waddling gait, which is what you expect with things like myopathies or muscular dystrophy, and that they have a Gowers sign when they get up from the floor, so they need to push off the floor, then push off their legs to rise.
And if you see a high-frequency, low-amplitude tremor, that’s a really big clue that this might be SMA, as we see that with SMA, but we don’t see that with a lot of muscle diseases.
We tend to think about reflexes being absent in everyone with SMA, but sometimes in the milder forms of SMA, reflexes may still be present. So if you see reflexes, that doesn’t rule out a diagnosis of SMA.
If you’re suspicious and want to be a little adventurous, you could try listening to muscles with your stethoscope, especially the bigger muscles. And you may hear muscle fasciculations, which sound like a popping or fluttering of the muscle.
