What is the medical term for when plantar stimulation causes the toes to dorsiflex?

Babinski Sign: Dorsiflexion of the Great Toe Following Plantar Stimulation

The Babinski sign refers to the dorsiflexion of the great toe, with or without fanning of the other toes, in response to stimulation of the plantar surface of the foot, indicating dysfunction of the pyramidal tract. 1

Pathophysiology and Clinical Significance

The Babinski sign represents an abnormal plantar reflex that occurs due to upper motor neuron dysfunction. Unlike the normal plantar reflex (which is a local S1 reflex), the Babinski sign is part of a broader defense reflexivity of the lower limbs 2.

When properly elicited:

• The characteristic response is dorsal flexion of the great toe through recruitment of the extensor hallucis longus muscle
• It may be accompanied by fanning of the other toes
• The response is often part of a flexion synergy involving other muscles that shorten the leg 3

Proper Technique for Eliciting the Sign

To properly assess for the Babinski sign:

• Stimulation should preferably be applied to the lateral region of the foot
• Use non-painful stimulation (typically with a blunt object like a reflex hammer handle)
• Observe not only the toe movement but also any simultaneous contraction of flexor muscles in the thigh 4
• The stimulus is typically drawn from the heel along the lateral aspect of the sole and then across the ball of the foot

Clinical Interpretation

The Babinski sign has significant diagnostic value:

• A positive Babinski sign (upgoing toe) indicates dysfunction in a specific fraction of the pyramidal tract 2
• This dysfunction involves the monosynaptic stimulation of extensor hallucis motor neurons and disruption of normal inhibitory pathways
• It remains a precise indicator of pyramidal tract dysfunction even 100+ years after its description 1

Differential Considerations

Several important distinctions should be made:

• Normal plantar reflex in adults: downward flexion of toes (plantar flexion)
• Babinski sign: upward movement (dorsiflexion) of the great toe with or without fanning
• In newborns: upgoing toes may be normal due to immature nervous system development 3
• "Pseudo-Babinski" responses may occur with peripheral nerve disorders 2

Historical Context

The sign was first described by Joseph Babinski, a French neurologist of Polish descent, on February 22,1896. He initially referred to it as "phénomène des orteils" (toes phenomenon), though it is now commonly known as the Babinski sign or extensor plantar response 5.

Common Pitfalls in Assessment

• Failing to distinguish between a true Babinski sign (part of the flexion synergy) and isolated upgoing toes that don't belong to this synergy 3
• Disregarding the association with the flexion synergy of the leg
• Improper stimulation technique or misinterpretation of withdrawal responses
• Not considering that the plantar response involves not just the toes but all muscles that shorten the leg 3

The Babinski sign remains a valuable clinical tool for neurological assessment, providing important information about the integrity of the corticospinal system with minimal equipment required.