The Babinski sign: the first hundred years.

The year 1996 marks the centenary of Babinski's description of the toe responses (normal and pathological) after stimulation of the sole of the foot. The upgoing toe response is normal in the 1st year of life and forms part of the flexion synergy of the leg, which had been known before 1896. Babinski also recognized the relation between the toe phenomenon (phénomène des orteils) in older children and adults and dysfunction of the pyramidal system. Neurologists became so fascinated by toe responses alone that many competing signs were proposed; most of these consisted of stimuli at other parts of the leg and were actually part of the same-but temporarily forgotten-flexion synergy. From 1910 to 1915 Marie and Foix and also Walshe re-emphasized this relationship and pointed out the analogy with the flexion reflex of the dog that had been extensively studied by Sherrington; the toe "extensors" shorten the leg and therefore they are flexors in a physiological sense. The normal (downward) toe response of the toes does not belong to a more complex movement, although Babinski originally believed this; it is a monosegmental skin reflex, akin to abdominal reflexes. Babinski correctly predicted that dysfunction of the pyramidal tract is not synonymous with a lesion, and that this dysfunction of the pyramidal system is necessary but not sufficient to produce a phénomène des orteils.