Testing for arm drift is a standard part of the simplified three-part neurological exam we all perform, technically called the Cincinnati Prehospital Stroke Scale. It’s a fairly crude examination, but when even one finding is positive in the right clinical scenario, there’s a pretty good likelihood that the patient has experienced a stroke. The problem is that testing for arm drift isn’t perfectly sensitive and it will miss a certain number of acute lesions that could be amenable to treatment.
One way to increase the yield of the physical exam is to expand beyond the basic maneuvers we are taught early in training. Doing so, however, has costs in terms of time and memory, two things we are often short of in emergency medicine. We can’t afford to be doing complete neurological exams, nor remember the numerous steps involved, but by adding a couple of simple, high-yield maneuvers to our repertoire we can really improve our patient assessment.
Arm Drift in Summary
First, let’s review what we’re already doing. The finding we really want to elicit with arm drift testing is actually called pronator drift, which has a bit more to it than just looking for unilateral arm drop. Like we all know, you start by having the patient hold their arms straight out in front of them at the level of the shoulders for 10 seconds (or 20, or 30, depending on who you ask). The trick most people know but don’t always utilize is that the patient’s eyes should be closed and their palms pointing towards the ceiling. If you’re not doing these last two parts, you’re giving up valuable information. A positive test will usually exhibit an inward rotation of the patient’s affected hand (pronation), plus-or-minus downward arm movement. In certain cases, however, you may actually see the affected arm move upwards; just know that a normal person should be able to keep both hands parallel. I also like to tap their hands downward after several seconds to look like I’m doing a deluxe exam and see if I can provoke any subtle weakness.
So onto our new concept: the “forearm rolling test.” Unlike most signs in medicine, I don’t believe this one has a fancy eponymous name meant to confuse medical students. To perform the exam, you have the patient hold their arms in front of them with their elbows bent at 90 degrees and forearms parallel to the ground. The patient rotates their arms around one-another in a circular motion for 5-10 seconds, then reverses direction. A positive test will result in the affected arm remaining fairly stationary while the good arm circles it. Pretty straightforward.
Forearm rolling test. Click image for source.
So below is the only video I could find on the internet demonstrating the maneuver. For best results, I suggest having your partner play a hand drum while you perform the exam. Glittery belts are strictly off-limits unless you are an attending neurologist.
Forearm Rolling (sorry I couldn’t get embedding to work)
I first came across this exam in a wonderful book called Evidence-Based Physical Diagnosis. For the forearm rolling test they listed a sensitivity of 87%, specificity of 98%, positive LR of 36.6, and a negative LR of 0.1 in identifying unilateral cerebral hemispheric disease. There’s not any discussion of the numbers outside of the table where they are listed, but they seem to come from a study by Sawyer et al in 1993.
Even without a full-text article available, it’s obvious that these numbers are too good to be applicable to a population outside of the very specific one studied. Still, the results certainly caught my attention and made a case for the arm roll being a potential useful tool. Reviewing a couple of textbooks and the abstracts from 3 or 4 other studies, the sensitivity of the test ranges anywhere from 24% to 98% depending on the population being studied. The important point is that it consistently outperformed pronator drift in the detection of cerebral lesions. It’s not perfect, but it’s probably an improvement.
There are two variations on the maneuver that I’ve come across in the literature, referred to as index-finger rolling and thumb rolling. The problem is that while they are mentioned fairly often, they are not well described and I don’t have access to any of the articles that might provide some elucidation. Why should you care about these? Well it appears that finger rolling may be even more sensitive for cerebral lesions than forearm rolling, with thumb rolling claiming an even higher sensitivity than both.
As a point of disclosure, I just came across these variations while researching this post and haven’t used either in clinical practice, but I will be certainly trying them in the near future.
CONJECTURE ALERT: My only source of information on how to perform this test comes from this one picture I stumbled across. It looks like it’s performed very similar to forearm rolling, but with the index fingers extended and the focus on rotating the hands as opposed to the entire arm.
Finger rolling. Click image for source.
Since most sources mention this as being superior to forearm rolling, I’m not sure why they even bother mentioning the latter anymore. Still, there’s not too much hard data out there so try out both and see what you like best. Here’s the one free full-text article I could find comparing the two, and a letter describing why it’s plausible that they could be useful in combination.
DOUBLE CONJECTURE ALERT: I don’t even have a picture of this one to go off, but I’m going to assume that thumb rolling as described in the neurology literature is basically the act of twiddling one’s thumbs. Amazingly enough, someone put a video of himself twiddling his thumbs on YouTube, so here’s the enthralling link if you’re not sure what I’m talking about.
There’s only one abstract I was able to find on the subject. The premise is that since finger rolling is better than forearm rolling, examining the even more distal thumbs will provide greater sensitivity as they are more likely to be affected by a CNS lesion. Again, this is pretty limited data and all I can suggest at this point is that you try it out and see if you like it.
So how do I plan on using these tests? Since drift is a standard part of the Cincinnati Prehospital Stroke Scale and commonly understood by emergency care providers of all levels, I don’t see it being replaced by rolling. Using the two in tandem certainly seems like a good idea to me, with almost no downsides. All of the rolling tests are so quick and easy to perform that the only negative would be the risk of a false-positive result.
In my limited experience the false-positive rate is small, easily predicted, and no worse than what you see in pronator drift testing. In fact, I find the forearm roll is actually a bit easier for the patients to perform than pronator drift testing. We see a lot of folks who are either too weak and lethargic to hold both arms up for a decent amount of time, or don’t follow directions very well and get distracted after a couple of seconds, so 5-10 seconds of active participation by having them roll their arms usually works pretty well.
Finger rolling will probably be my new default maneuver over forearm rolling. The consensus in journal articles and neurology texts seems to be that it is more sensitive, plus I imagine that it also is a bit easier for the patient to perform. I’ll still have to try them out in tandem for a bit to make sure this pans out, but I don’t foresee any issues.
As for thumb rolling, I’m much less sure how this is going to fit in at this point. For now it will just be something I play around with when I have the opportunity. If I decide I like it, I’ll update this page to reflect my experience.
So get out there, do some exams, and let me know what you think.