Babinski reflex

(-skēz)
n.
An extension of the great toe, sometimes with fanning of the other toes, in response to stroking of the sole of the foot. It is a normal reflex in infants, but it is usually associated with a disturbance of the pyramidal tract in children and adults. Also called Babinski sign, Babinski's sign.

[After Joseph François Felix Babinski (1857-1932), French neurologist.]

The involuntary raising of the big toe upon stroking the side of the foot. The reflex is present in adult apes and in human infants, but disappears in humans at about 18 months, when it is inhibited by higher centres. The inhibition is lost in tabes dorsalis (the degeneration of the posterior ascending fibres of the spinal cord that occurs in tertiary syphilis) and in other diseases of the brain and spinal cord. It is believed that the reflex is useful for grasping the branches of trees with the toes, and that the inhibitory mechanism was developed late in primate evolution, when apes forsook the trees to walk on the ground. It is a useful diagnostic reflex, and was discovered by the French neurologist Joseph Babinski (1857–1932).

(Published 1987)

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A reflex action of the toes, indicative of abnormalities in the motor control pathways leading from the cerebral cortex. It is elicited in dogs and cats by an upward stroking of the metacarpal or metatarsal bones. A normal reaction is slight flexion of the toes. In a positive sign, the toes extend; seen with upper motor neuron lesions. Called also Babinski sign.