Images in Clinical Medicine

The Babinski Sign

Francis A. Neelon, M.D., and Elisabeth N. Harvey, M.S.W.

N Engl J Med 1999; 340:196January 21, 1999

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Figure 1 As a 5-month-old infant and his 30-month-old brother sat together for an informal portrait, the pressure of the infant's right great toe against his left sole induced reflex dorsiflexion of the left great toe. This reflex phenomenon constitutes one of the most famous signs in medicine: the Babinski reflex. The Babinski reflex is present in normal newborn infants and disappears as the central nervous system matures. Persistence of the reflex after the age of three years or its reappearance in later life indicates dysfunction of the pyramidal tract. The stimulus needed to elicit the reflex sign need not and should not be painful. Gentle pressure or stroking of any part of the leg may evoke the response, but the most effective method is stimulation of the sole of the foot. The hallmark of the Babinski reflex is contraction of the extensor hallucis longus muscle. Careful observation for tightening of the extensor tendon of that muscle may allow one to determine whether the Babinski sign is present or not.

Francis A. Neelon, M.D.
Duke University Medical Center, Durham, NC 27710

Elisabeth N. Harvey, M.S.W.
Family Services of Greater Lowell, Lowell, MA 01852

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