Plantar Response

Plantar Response

The plantar response is most commonly elicited by stroking the sole of the foot with a blunt object. The first response of the hallux is the critical observation, which may be facilitated by having ones line of vision directly above the axis of the toe. The normal response after maturation of the corticospinal tracts (i.e., after about three years of age) is for the big toe to flex. An extensor response of the big toe in an adult (Babinski’s sign), with or without fanning (abduction) of the other toes (fan sign, signe de l’éventail), is a reliable sign of upper motor neurone pathology. Use of the term "negative Babinski’s sign" or "negative Babinski response" to mean "flexor plantar response" is incorrect and should not be used. This normal plantar response is a superficial cutaneous reflex, analogous to abdominal and cremasteric reflexes, whereas the pathological response is often accompanied by activity in other flexor muscles. In some individuals the toes do not move at all, in which case the response is labeled as "mute" or absent. Assessment of the response may be confounded by withdrawal of the foot in ticklish individuals. Differentiation from the striatal toe seen in parkinsonian syndromes is also important.
The plantar response may be elicited in a variety of other ways which are not in routine clinical use. Of these, perhaps the most frequently used are Chaddock’s sign (application of a stimulus in a circular direction around the external malleolus, or the lateral aspect of the foot from heel to little toe) and Oppenheim’s sign (application of heavy pressure to the anterior surface of the tibia from patella to ankle). These may be helpful in ticklish patients who object to having their feet stroked. If the plantar response thus elicited is upgoing, this suggests a spread of the "receptive field" of the reflex. Babinski’s sign is the first to occur in the presence of upper motor neurone pathology.
It is often difficult to form a definite judgment on the plantar response and reproducibility is also questionable. A study of 24 experienced clinicians invited to examine plantar responses "blind" found that the interobserver percentage agreement beyond chance was on average only 16.7% (95% confidence interval [CI] 0.4-33%); intraobserver percentage agreement was a little better (average 59.6%; CI 39.679.6%). There remains a persistent belief, particularly amongst trainees, that an experienced neurologist can make the plantar response go which ever way s/he chooses.

References

Maher J, Reilly M, Daly L, Hutchinson M. Plantar power: reproducibility of the plantar response. BMJ 1992; 304: 482
Van Gijn J. The Babinski sign: a centenary. Utrecht: Universiteit Utrecht, 1996

Cross References

Abdominal reflexes; Babinski’s sign (1); Chaddock’s sign; Gordon’s sign; Oppenheim’s sign; Reflexes; Striatal toe; Upper motor neurone (UMN) syndrome