Overview of the Autonomic Reflex Screening
Transcript: Overview of the Autonomic Reflex Screening
When we do autonomic testing, what do we really want to accomplish? Well obviously, we want to detect if autonomic failure is present or not, that’s obvious. We also want to be able to have tests that allow us to grade the severity of deficits that are present, and also to get some sense as to is this is a more localized, a more focal problem, or is this a more widespread problem. What’s the distribution of autonomic failure? And then in some cases we’re actually able to detect where the lesion is. Is this more of an autonomic neuropathy, ganglionopathy or even a central autonomic disorder? And with the right autonomic tests you can narrow that down further.
Now when we choose a test for autonomic function testing, there are certain attributes we would like the test to have in order to implement it into routine testing. Again, there are some obvious ones here. The test has to be sensitive; it has to be specific, obviously. It should also be reproducible from day-to-day and from week-to-week. It should be relevant clinically, so obviously you want to test someone’s blood pressure responses if they have blood pressure problems, or their sweat function, if they have sweat problems, so there should be some clinical relevance to it. And the test should have some form of physiological basis. You don’t want a black box where you put something in, you don’t know what happens, you get some sort of result output, and you don’t know really what that result is or means. So, it should be physiology based. And then ideally you want a test that’s not invasive. That’s practical, that you can perform in a 10-year-old just as well as an 80-year-old. And you want a test that you can easily implement without being an engineer yourself, a test package that you can purchase and get ready and running without that knowledge. And then you want a test that is well tested and validated for confounding factors other than disease, and we’ll get into that in detail here in a little bit.
So, with all that in mind, what I will be talking here mostly is the autonomic reflex screen. This is a test battery that was established over 30 years ago. Phillip Low and colleagues were the pioneers getting that battery started, and this standardized testing battery has been essentially unchanged for those past 30 years. It’s been extensively validated, it’s been used in studies over studies. We do about 4,000 of those a year at Mayo Rochester alone, and this testing battery has been adopted into commercially available equipment with dedicated software and is available for standardized testing now at other institutions as well and increasingly found across the country. The battery of tests I’m talking about assess sudomotor function, cardiovagal function and cardiovascular adrenergic function. And I’ve listed CPT codes here because we do a test, you want to be able to bill for it and in fact, the CPT codes have been built around the test that I’ll be presenting. They cover some other tests as well, but this is how they actually got originally started.
So, the autonomic reflex screen consists of 4 parts. There’s the assessment of sudomotor function and specifically postganglionic sudomotor function using a test called the quantitative sudomotor axon reflex test or QSART. Then we look at heart rate responses to deep breathing to assess the cardiovagal function. We look at Valsalva maneuver to look at both cardiovascular adrenergic and cardiovagal function, and we look at a head up tilt, mostly looking at cardiovascular adrenergic function. And, this table, this is a little busy, but it basically shows you that the test we’re doing fulfill all those attributes that I mentioned before: sensitive, specific, reproducible, physiologic basis, etc., and so this is really how they got into that battery from the first place.
Wolfgang Singer, MD
Associate Professor of Neurology
Mayo Clinic Rochester, MN