THE BABINSKI RESPONSE: A REVIEW AND NEW OBSERVATIONS

REVIEW OF THE ANATOMICAL EVIDENCE Probably the most famous sign in clinical neurology is the plantar response described by Babinski. Babinski wrote that this sign indicates a disturbance of function of the pyramidal system. Textbooks usually state, however, that this sign indicates a lesion of the pyramidal tract, and so one might well imagine that the significance of such a well established sign had been amply proved. There are four points concerning the Babinski response that need to be stressed: (1) Babinski stated that his sign " parait etre"; he was not definite about the matter. (2) Babinski eventually described two forms of abnormal plantar response. These are separate and clearly different. There is " Extension des orteils et plus particulierement du gros orteil: j'ai appele ce mouvement 'le phenomene des orteils', et mes collegues ont bien voulu le denommer ' le signe de Babinski' (1904). There is also: "L'excitation de la plante du pied provoque parfois, entre autres mouvements reflexes, une abduction plus ou moins marquee d'un ou de plusieurs orteils" (1903). Although Babinski observed that the latter sign can be found in the normal, it is particularly common in subjects "atteints d'une perturbation du systeme pyramidal ". Dupre named this sign, " le signe de l'eventail ". It is usual, at least here in Britain, to speak of the Babinski response only when both these signs are present. But many workers consider the extension of the great toe as the essential sign, and speak of the Babinski response when only this sign is present. (3) The phenomenon was described as a disturbance of functioning. Babinski at first held the opinion that there need be no anatomical or histological lesion of the pyramidal tract to account for the presence of this sign. Indeed, he recorded the presence of the sign in a case of strychnine poisoning; when the poisoning passed off, the abnormal sign gave way to the normal response. Babinski thought that the sign could be the first and only evidence of this disturbance in functioning. Thus it did not seem to Babinski that it was necessary to give any histological verification of damage to the pyramidal tract. As he said later (1922), he was content " a se cantonner dans le domaine de I'observation clinique ". (4) It is clear that Babinski used various methods of stimulation to obtain the response. In his original description of extension of the toes (1896), he described the stimulus as a " piqfire de la plante du pied ". In his more detailed and important communication on the new sign (1898), he wrote of the effects of stimulating the internal part and the external part of the plantar surface. And he also wrote that in some subjects it is necessary to prick the plantar surface of the foot to elicit his reflex. Babinski's sign met with immediate success; and as an additional sign of hemiplegia and crural monoplegia it deserved the success. This was doubtless what Babinski intended the new sign to be; for in his time terminology was less precise than it is now. It is likely that to Babinski the terms " a sign of hemiplegia " and " a disturbance of function of the pyramidal tract " were equivalent. However, when anatomical evidence presented itself, it began to be obvious that Babinski's statements were wrong. Babinski himself reported cases which did not accord with his previous statements. For instance, in 1899, he reported three cases of paraplegia in flexion. He stated that in all three there was no histological evidence of degeneration of the pyramidal tract. Yet in the first case, the plantar responses were normal, in the second case, the " phenomene des orteils " was present, and in the third case " tickling the plantar surface of the foot gives reflex movements of the whole limb". As Babinski was concerned in this paper with demonstrating that there is such a thing as paraplegia in flexion without involvement of the corticospinal tracts, he seems to have failed to realize that he had recorded different forms of plantar response, one of which was the Babinski response, all present with normal cortico-spinal tracts. On his own premises, his Case 2 proved his supposition 250 P rocted by coright.