Melissa Wright, MD, PhD, discusses early signs of adult-onset SMA, including progressive fatigue, weakness, falls, and hand tremors.
When should fatigue or finger tremors prompt a closer look for SMA?
Transcript
Adult-onset SMA can be a particular challenge to diagnose. Aside from being really rare, so it’s often not at the top of anyone’s mind, it can present insidiously with seemingly vague symptoms.
Adults will often notice fatigue or a decrease in endurance for things that they used to be able to do easily early in the disease course. In retrospect, once you make the diagnosis of SMA, everyone realizes that fatigue was actually the patient having some weakness, but it wasn’t enough weakness for them to realize that’s what it was.
Fatigue that’s caused by SMA is usually progressive, and it may be noted with things that use proximal muscles, especially the hip girdle, more than anything else.
So they may tell you that they get tired with things like climbing stairs, or getting up from the floor, or walking for a long distance, getting in and out of a car, doing their normal leg workout at the gym, things like that, and that it’s been getting worse over the last several months or even the last several years.
They may also start to complain about falls, which is atypical for most patients who have weakness for other reasons.
If you hear these complaints and you see subtle signs of weakness on your exam, such as a waddling gait or difficulty getting up from the floor, getting out of a low chair, and especially if their reflexes are absent, you should think about SMA as a possible cause for their fatigue.
It’s important to keep in mind that milder forms of SMA may still have reflexes present, so having reflexes doesn’t rule out the diagnosis of SMA.
Another early sign of adult-onset SMA is a tremor that’s oftentimes most notable in the hands. The tremor is low-amplitude but high-frequency and a little bit irregular. The technical name for it is polyminimyoclonus, but it looks like a low-amplitude high-frequency tremor.
If an adult comes in with a tremor like this, it’s important to ask them questions about strength and fatigue and to look for other signs of SMA when you do their exam.
