Value of self-induced plantar reflex in distinguishing Babinski from withdrawal

Interpretation of the plantar response can be difficult, resulting in inter- and intraobserver discordance. A common source of confusion is that tickle-induced withdrawal can cause dorsiflexion of the great toe in a pattern similar to the Babinski sign.

Ticklish sensation, present when the stimulus is introduced by a person other than the subject, is reduced by self-stimulation. The cause of this inhibition has been shown to be in the cerebellum.¹

We reasoned that self-induction of the plantar response should reduce withdrawal, obviating the potential confusion with a Babinski sign. The patient would sit down, grab the foot, and scratch the sole with a sharp object in a posture similar to the famous Greco-Roman Spinario sculpture of a boy withdrawing a thorn from the sole of his foot, studied and drafted by Peter Paul Rubens (1577–1640) (figure).

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Figure Spinario

Sir Peter Paul Rubens' 1601 study of the famous Greco-Roman sculpture, showing a person removing a thorn from the sole of his foot. © The Trustees of British Museum; reproduced with permission.

In the process of reviewing the available literature, we were surprised to discover that C. Miller Fisher² had reported this observation 4 decades ago.

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• © 2016 American Academy of Neurology