Brouhaha Over Babinski: Debate Centers on Usefulness of Test

February 3, 2006

In the late 1890s, Joseph Francois Felix Babinski (1857-1932), a French neurologist of Polish descent, discovered that if noxious stimulation of the sole of a patient's foot caused the big toe to rise and the other toes to splay, the reflex was indicative of corticospinal tract damage. "

In the late 1890s, Joseph Francois Felix Babinski (1857-1932), a French neurologist of Polish descent, discovered that if noxious stimulation of the sole of a patient's foot caused the big toe to rise and the other toes to splay, the reflex was indicative of corticospinal tract damage. "It made him so famous he was considered for a Nobel Prize," said neurologist Michael Graves, MD, director of the Electromyography (EMG) Laboratory and the Neuromuscular Program at the University of California, Los Angeles (UCLA), in an interview with Applied Neurology. Babinski did not get the Nobel Prize, but his sign became an indelible part of neurology.Today, some 110 years later, mere mention of the utility of the Babinski sign engages the attention of neurologists, said Graves, "because everybody accepts it as an article of faith." So embedded in the standard neurologic examination is the Babinski sign that to suggest research into its reliability is "like going into the Vatican and asking, 'How come the Pope has to be a Catholic? Why don't you let a Presbyterian do it once?'" added Graves.Last year, however, neurology researchers Timothy M. Miller, MD, PhD, of the University of California at San Diego, and S. Claiborne Johnston, MD, PhD, of the University of California at San Francisco, assumed the challenge and ventured into territory where few others have dared to tread. They tested the Babinski sign as an indicator of upper motor neuron weakness and questioned whether it should be a part of the routine neurologic examination.1 Miller and Johnston found that the Babinski sign was unreliable and a poor predictor of upper motor neuron weakness. Testing for speed of foot tapping was more reliable, sensitive, and specific. Moreover, results were the same whether the Babinski test was performed by a neurologist or by a primary care physician.The fallout was immediate. Neurologist William M. Landau, MD, of the Washington University School of Medicine in St Louis, condemned the study design and methodology in a satirical, icy editorial.2 "The authors of the paper confuse an involuntary physiologic test with a test of voluntary task performance-these are 2 different kinds of phenomena . . . qualitatively different . . . not properly comparable," said Landau in an interview. "There's no question the Babinski sign is reliable. The whole point of my criticism is that an abnormal reflex is a useful observation, which has nothing to do with a test of performance. It's like comparing apples to bananas."Landau also faulted Miller and Johnston for not conducting "side-to-side comparisons of how their participants checked for the Babinski sign. There are some specifics in how [the Babinski reflex test] is done and it should be done the same by everybody who's doing the test," he said.Miller and Johnston weren't surprised by Landau's critique. "It's exactly the kind of response we expected from master clinicians, from the old guard, because we're questioning something that's very dear to neurologists," Johnston told Applied Neurology."Landau is right about apples and bananas," Johnson continued. "Physiologically, the Babinski sign and foot tapping are entirely different tests. But it wasn't our goal to compare the 2 directly. Our goal was to see whether either test, operationally, as it's used by current practicing neurologists and by primary care physicians, had value in predicting whether a lower extremity is weak."While Landau focused on pathophysiology and the underlying science of the arcs and all that stuff in his editorial, at the end of the day, we were just looking at this empirically: is Babinski likely to be useful as a sign of upper motor neuron weakness? Our goal was much more circumscribed, and we feel we did a pretty good job of that," said Johnson."We are trying to provide real data in a controlled setting on the practical utility of these tests. To me, if a test requires such detailed teaching and someone watching over your shoulder in order for it to work right, then it makes you question whether it's going to be useful for general care practitioners and primary care physicians," he concluded.BALANCED VIEWDampening the firestorm that the Miller-Johnston paper set off was a commentary3 by Robert G. Holloway, MD, associate professor of neurology at the University of Rochester, NY. He noted that although neurologists have refined the uses of the plantar reflex during the past century, "little has been done to explicitly define these roles and the teaching of the plantar reflex in clinical neurology continues to occur in haphazard, apprenticeship fashion."3 While Holloway applauded the Miller-Johnston study as "a step in the right direction" and proof that "such assessments can be done," his article also lent credence to Landau's analysis of the study's shortcomings."We haven't approached the use of the plantar reflex as we would a diagnostic test," Holloway told Applied Neurology. "It's implicit in the way we actually do our exam, yet we learned how to use it in various scenarios almost as an apprentice would. It's one test with many different uses; therefore, it's probably 15 to 20 different tests and could be studied specifically as a diagnostic test with multiple uses. But we have never really thought about it that way." At the same time, "just stroking a foot behind a curtain is a very unrealistic situation," he added. "When you're taking a history and know what you're looking for, the Babinski test" can help a clinician refine his or her diagnostic suspicions.That said, Holloway agreed that in certain circumstances, the Babinski sign might not be useful, but other tests might be. "Where you have long-standing upper motor neuron disease, there are other neurologic signs that are better than plantar reflex, and most neurologists know that already. Good neurologists do check the speed of foot tapping because it is a great marker to elicit subtle differences in upper motor neuron function. Another great test to elicit that subtle difference is the forearm rolling test, which [clinicians] don't often use but is actually very good, probably better than the Babinski sign in terms of upper motor neuron function," he said.Miller and Johnston claim that the way the test is being taught is making it less useful. "There is no question that the test has utility in specific settings. We're definitely not proposing that it be thrown out, and we're certainly not saying that in the hands of Bill Landau or other master clinicians that Babinski isn't a reliable test," Johnston said. "We can say that, in a representative population of neurologists and primary care physicians, it's not working. [Also,] the foot tap test is not a generally recommended standard part of a neuro exam, yet the Babinski sign is."Perhaps most disconcerting was the finding by Miller and Johnston that skill and experience in conducting the Babinski test didn't account for much. "If it mattered a lot then we would have seen big differences between the performance of neurologists and the performance of primary care physicians, and we didn't see that," said Johnston. "We expected that the neurologists would do really well and that the primary care docs wouldn't."Holloway, however, challenged that finding. "The good diagnostician is someone who does not [scrape] the foot in isolation. If [the study participants] had been neurologists who were taking a history and, in addition to entire assessment, did the Babinski test, I guarantee that their ability to interpret the sign would be much more informed than those who are not neurologists."NEUROLOGISTS RESPONDSince publication, both Johnston and Landau have gotten considerable feedback. Most of the responses to their study, said Johnston, have been positive. "Some neurologists just can't believe it's true, and the letters have been pretty interesting. One neurologist wrote that he had stayed up late for 2 nights, rolling over in his sleep, worried that a sign he took so dear was being unseated. But most people have congratulated us in trying to raise the bar and bring science to what has been based on lore." Landau, meanwhile, said that he has received "more fan letters than I ever had."As the old guard gives way to the new, there is a growing belief that neurology researchers need to find the science behind the age-old teachings to determine how best to use the limited time one has to evaluate a patient. "We need carefully controlled, carefully done studies, and we need to question authority and dogma and aphorisms because they are nonscientific," said Johnston. "We need to question what elements should be retained in a standard exam and that's what we were trying to do. When the patient-encounter for a primary care physician is only 12 minutes long at best, spending 30 seconds of that on a test that may have less utility than other carefully selected tests may not be the best way to spend that time. For a primary care physician or emergency room physician doing an exam on a patient to decide whether he or she has had a stroke or not-when I see [the clinician] stroking a foot instead of doing foot-tap or pronator drift test, it just makes me question whether we're teaching them most appropriately."Graves suspects that many neurologists and general practitioners no longer test for the Babinski sign because they don't think it's useful in the new world of MRI scans. But solid research that supports the utility of clinical signs is important if for no other reason than that a diagnosis based on clinical signs is far less expensive than a diagnosis based on MRI findings."The Miller and Johnston work is important because it demonstrates that you can collect data on these things and do a lot of interesting analysis. They have actually collected objective data and conducted research on clinical signs, which is something that is sorely missing in neurology," Graves continued. "Dr Landau's critique is well received, but it tends to be the expert opinion of an older, experienced clinician rather than objectively collected data from the clinic.""Judicious use of the neurologic exam is critical, and how one can know how to approach certain circumstances and know when to use the best predictive tests or the best tests is something that has not been well studied," agreed Holloway. He noted that the controversy about the Babinski sign has generated such emotionalism because the sign, in some ways, defines neurology. "It's such an historically important sign that has really risen to the level of almost part of what makes a neurologist a neurologist. Therefore, the emotions that come along with it are very real. At the same time, there is very little research. There have been some studies that have tried to determine the diagnostic value of our exam in its components but not much."The brouhaha over the Babinski sign comes down to the rift between experience and evidence-based medicine, Holloway posited. "Experience-based medicine [derives from] the master clinicians who have all these hundred years of experience of defining its role and use that we implicitly know, kind of like these internal scripts we use. But not everything is defined or written down, because it's almost too complex to do that, and it is creating a tension between experience and evidence-based medicine."Beyond stirring up the dust and igniting discussion and debate, the Miller-Johnston study has served to encourage others to consider research into clinical signs used in diagnostic neurology, despite the difficulty in finding funding for such "low-tech" tools. In fact, Graves, who for the past 2 years has been collecting data on all 22 bedside clinical neurologic signs used to diagnose amyotrophic lateral sclerosis-including the Babinski sign-had been reluctant to publish his findings because, in his view, research was "too controversial." "This has stimulated me to get my research written up and submitted," he said.MORE TO COMEFor Miller and Johnston, the study is the first of many to come. "We're planning on going through the neuro exams slowly and looking at different elements and their utility in the hands of neurologists and general practitioners. So there will be a slow stream of these things over a long period of time. When you think about 2 minutes per hour for a neurologist in a given day-and every neurologist in every clinic and all these [emergency] docs using the Babinski test-it's really a huge consumption of health care resources, and every consumption needs to be evaluated carefully and scientifically."We certainly applaud our elders in discovering these signs and developing an understanding of their pathophysiology, but that doesn't necessarily make them empirically useful in evaluating patients. Our tests need to be simple, easily taught, and sensitive. Seeing a response like Landau's actually makes me feel better about the work we're doing [about] how important it is to get this stuff out there," Johnston said in conclusion. "Just having people discuss it and think about it, and, yes, even roll over in their beds at night [about it]; that's a good thing."AJS Rayl, MA, is a freelance writer in Malibu, CA.REFERENCES:1. Miller TM, Johnston SC. Should the Babinski sign be part of the routine neurologic examination? Neurology. 2005;65:1165-1168.2. Landau WM. Plantar reflex amusement: misuse, ruse, disuse, and abuse. Neurology. 2005;65:1150-1151.3. Holloway R. The Babinski sign: thumbs up or toes down? Neurology. 2005;65:1147.