History of the extensor plantar response: Babinski and Chaddock signs.

The testing of reflexes involving the lower extremities is a pivotal part of the modern neurological examination. The normal response to noxious stimulation of the foot is plantar flexion of the toes, causing them to curl downward toward the undersurface of the foot. In 1896, Joseph Babinski described an extensor toe response that he claimed was a consistent finding among patients with pyramidal tract lesions of the cortex, subcortex, brain stem, or spinal cord. He considered it a distinct sign of organic disease and found it to be absent in cases of hysterical weakness. Charles Gilbert Chaddock admired the work of Babinski and described a modification of the Babinski technique, demonstrating that stimulation of the lateral surface of the foot could induce the same type of toe extension in patients with pyramidal tract lesions. The two reflexes are complementary, and each can occur without the other, although both are usually present in cases of pyramidal tract impairment. Although these two reflexes are the most commonly described pathological reflexes indicative of pyramidal tract disruption, the names of other celebrated neurologists are also linked to the study of extensor toe signs, each having identified a variant of the Babinski sign.