Andrew N. Wilner, MD; Sayyed A. Sohrab, MD


July 16, 2014

Editor's Note: While onsite at the American Academy of Neurology 66th Annual Meeting, held in Philadelphia, Pennsylvania, from April 26 through May 3, 2014, Medscape correspondent Andrew N. Wilner, MD, interviewed Sayyed A. Sohrab, MD, Assistant Professor, Department of Neurology, University of Michigan School of Medicine, about his poster looking at a possible way to improve upon the traditional neurologic exam.[1]

Andrew N. Wilner, MD: The Babinski sign has been around for a long time. Looking at your poster, have you found a way to improve upon it? What did you do?

Dr. Sohrab: The idea came from the work of Dr. Blakemore[2] and colleagues in the United Kingdom in 1998, showing that the anterior cerebellum is involved in suppression of the withdrawal (or "ticklish" sensation).

Dr. Wilner: When you do the Babinski on some people, they just pull away, which makes the whole exercise useless.

Dr. Sohrab: Exactly, and the sole of the foot is one of the most sensitive parts of the body to stimulate. We postulated that if ticklishness is suppressed by the cerebellum, and the patient did the Babinski on him- or herself, we could abolish the withdrawal reflex. We put it to test with a curved instrument to make it easier for the patient. In people who had no central lesion, the toes curled under (toward the bottom of the foot) when they did the test to themselves. As you can see in the video, the genuine Babinski sign, in patients with a proven lesion, persisted, even when it was performed by the patient.

Dr. Wilner: You were able to eliminate false positives. In people whose toes moved upward (towards the top of the foot) when tickled, when they did the test to themselves, their toes curled downward, as you would expect them to.

Dr. Sohrab: After we submitted our poster, it was brought to our attention that in 1986 the same observation was made by Dr. Martin Weinstein[3] in a brief communication to Hospital Physician. [Editor's note: The article was published in Neurology.]

Dr. Wilner: The idea of self-stimulation [was reported previously]?

Dr. Sohrab: Yes. Apparently it was reported previously, and it is referenced in the footnote. As such, we make no claim to novelty, but we have made an independent observation.

Dr. Wilner: Have you done a series? Did you, for example, test 100 patients to see how many responded one way and how many responded the other? Did you determine how many responses you could correct, and how often we are interpreting a withdrawal response incorrectly as a Babinski? Are you planning to do that?

Dr. Sohrab: We are recruiting patients and are happy to work with collaborators. We want to show the positive predictive value and specificity of doing the test as a patient self-test vs the conventional method for testing the Babinski reflex by an examiner.

Dr. Wilner: Patients with large cerebral hemispheric lesions and who are hemiplegic may have trouble doing this themselves. What kind of pathology would be typical for a patient who has a positive Babinski but is still able to follow commands and do the test themselves?

Dr. Sohrab: In our abstract we explain that those cases are typically not equivocal. In other words, in a plegic or paralytic patient, there is usually enough evidence otherwise to show that this is an upper motor neuron lesion. Most of the trouble occurs when the patient has at least partial or no strength in the legs. It is in those equivocal cases that this method helps.

Dr. Wilner: What lesion would cause a positive Babinski? Are these brain or spinal cord lesions?

Dr. Sohrab: A positive Babinski sign indicates a central lesion, and it can be brain or spinal cord. With any of those lesions, you can expect a positive Babinski. If the plegia prevents any movement of the limbs at all, we rely on other evidence.

Dr. Wilner: You wouldn't need a Babinski sign in those cases.

Dr. Sohrab: The significance of an upward toe movement in that situation is probably much less than in someone who walks into your office and has an upward-moving toe when tested.

Dr. Wilner: Dr. Babinski would be pleased that you are continuing to refine his diagnostic test. Thank you very much for explaining your very interesting poster.


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