An extensor toe response can be elicited by a number of maneuvers, each of which has its own eponym. One of them is the Bing sign, which is intuitively appealing as we practice it by poking the dorsum of the great toe with a pin to see if the toe will extend into the pin rather than flexing away. Performing the reflex in this manner seemingly confirms that an upgoing toe is not just a sensitive patient's withdrawal response, as a voluntary withdrawal would not move towards the noxious stimulus. Given our enthusiasm for the Bing sign, we wondered what its reliability and validity would be. Interestingly, as opposed to the Babinski,1,–,4 Chaddock,1,2,4 Oppenheim,1,2,4 and Gordon,1,4 which have been subject to published studies of reliability and validity, the Bing does not have any published validity studies. More surprisingly, some articles do not even include the Bing sign among the list of such maneuvers, and in DeJong's The Neurologic Examination, it is listed among the minor extensor toe signs and demoted along with other techniques to the category of “clinical parlor tricks.”5 None of the articles that include the Bing sign provides a reference. Because the specific technique to elicit the Bing sign in recent texts is disputed5,–,10 (table), and standard neurologic examination sources in the intervening period do not include such information,11,–,18 we sought to clarify what Dr. Bing actually described.
Methods of eliciting the Bing sign according to recent texts
Who was Dr. Robert Paul Bing?
Dr. Robert Paul Bing (May 8, 1878–March 15, 1956) was a famous Swiss neurologist, lauded in his obituary as “one of Europe's most illustrious neurologists”19 (figure). He received his medical degree from the University of Basel in 1901 at the age of 23 with a dissertation on congenital muscle defects. He pursued an international neurologic education—training with Hermann Munk in Berlin, Ludwig Edinger in Frankfurt, Victor Horsley in London, and Joseph Dejerine and Joseph Babinski in Paris.20 Back home in Switzerland, he advocated for the field of neurology, leading a campaign to recognize neurology as a specialty and founding the first neurology walk-in clinic in Basel in 1907.21 He was a founding member and president (1919–1922) of the Swiss Neurological Society. He was known for his passion for neurology and published some 200 articles in addition to his textbooks, the Kompendium der Topischen Gehirn- und Rückenmarkdiagnostik,22 which appeared in 14 editions, and Lehrbuch der Nervenkrankheiten,23 with 9 editions. Both textbooks were widely read and translated into multiple languages. The first edition of Nervenkrankheiten also included a headache that he called “erythroprosopalgia,” which today is sometimes referred to as Bing-Horton syndrome or more commonly, cluster headache. He was a professor of neurology at Basel, achieving the status of full professor on April 12, 1932.20 Just 2 weeks prior to his death in 1956, he was described as delivering “a vigorous lecture, still abounding with those refreshing ideas which for a half-century had brought graduates in neurology to him from all corners of the earth.”19 Even after death, he has continued to promote the field of neurology by donating his assets to the Swiss Academy of Medical Sciences for creation of the Robert Bing Prize. The Robert Bing Prize of CHF 50,000 is awarded to “scientists who have done outstanding work which has helped in the recognition, treatment and cure of neurological diseases.”24
What did Bing describe?
One of Bing's earliest references to variations on the Babinski seems to be in a 1915 article where he does not label the sign with his name but describes25 “Nade[l]stich über dem 4. oder 5. Os metatarsale” or “a needle stick over the 4th and 5th metatarsal.” This is mentioned again without claiming it as the Bing sign in a 1918 publication26: “wovon wir hier exempli causa nur den Nadelstich über dem vierten oder fünften Mittelfussknochen anführen wollen” or “here, as an example, we only want to mention the needle stick over the fourth or fifth metatarsal bones.” Bing's23 Nervenkrankheiten in its earliest iterations makes no mention of a needle stick over the dorsum of the foot and references only the Babinski and the Oppenheim reflexes. In a 1919 edition of the Kompendium, he describes “einen Nadelstich auf den Fußrücken” or “needle stick over the dorsum of the foot” as a variant of the Babinski,27 but does not attach his name to it until the 3rd edition of his Nervenkrankheiten in 1924.28 While his later publications add the eponym, they do not specify where on the dorsum of the foot the sign is best elicited, although his earlier works would imply it is over the 4th and 5th metatarsal bones or the dorsolateral foot. To clarify, the Bing sign should be distinguished from what Bing initially described in another 1918 article,29 which was later dubbed the Bing or “Bingscher” reflex or the “paradoxic ankle reflex,” and believed by Bing to be a marker of spasticity. This Bing reflex, described as tapping on a line between the external and internal malleoli of the ankle with the foot dorsiflexed and looking for plantar flexion, was dismissed by Wartenberg11 as being “neither paradoxic nor indicative of a pyramidal lesion.” In reviewing the literature and in our own clinical practice, while the Bing sign of the eliciting an upgoing toe has lived on, the Bing reflex of eliciting plantar flexion has seemingly fallen to the wayside, although is potentially still in use in some countries, including the Czech Republic.30
Who first described poking the dorsum of the great toe?
As best we can tell, Bing did not describe poking the dorsum of the great toe with a pin. Despite the appeal of the name, this sign should probably not be attributed to Bing. One of us (P.D.S.) taught the technique of poking the great toe to numerous trainees at the University of Washington and in turn may have learned this modification of the Bing sign during internship at Boston City Hospital in 1958–1959 or subsequently during neurology residency at Johns Hopkins. Of note, Denny–Brown's 1946 and subsequent 1957 edition of the Handbook of Neurological Examination and Case Recording disparages alternatives to the Babinski sign and make no mention of the Bing sign.12,15 We are not alone in our inadvertent variation of the Bing sign, as others also suggest this technique.8,–,10 Future studies may be warranted to test this sign's reliability and validity in comparison to our neurologic standard, the Babinski. In the meantime, we invite others to educate us about who else may have started poking the dorsum of the great toe.
Author contributions
Dr. Davis drafted the initial manuscript and along with Dr. Longstreth proposed the initial concept of this paper. Dr. Wettstein served as our chief translator. All authors contributed by assisting in research, drafting, editing, and reviewing the manuscript.
Study funding
No targeted funding reported.
Disclosure
The authors report no disclosures relevant to the manuscript. Go to Neurology.org/N for full disclosures.
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received January 8, 2018.
- Accepted in final form June 14, 2018.
- © 2018 American Academy of Neurology
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