B

Abstract

Babinski’s sign is a polysynaptic cutaneous reflex consisting of an extensor movement (dorsiflexion) of the big toe on eliciting the plantar response, due to contraction of extensor hallucis longus. There may be in addition fanning (abduction) of the other toes (fan sign; signe de l’éventail) but this is neither necessary nor sufficient for Babinski’s sign to be judged present. There may be simultaneous contraction of other limb flexor muscles, consistent with the notion that Babinski’s sign forms part of a flexion synergy (withdrawal) of the leg. The use of the term ‘negative Babinski sign’ to indicate the normal finding of a downgoing (flexor; plantar flexion) big toe is incorrect, ‘flexor plantar response’ being the appropriate description. The plantar response is most commonly performed by stroking the sole of the foot, although many other variants are described (e.g. Chaddock’s sign, Gordon’s sign, Oppenheim’s sign).