Which sign involves dorsiflexion of the big toe following stimulation of the lateral sole?

• A. Kernig's sign
• B. Brudzinski's sign
• C. Nuchal rigidity sign
• D. Babinski sign

Answer: (D)

Babinski sign is the dorsal extension of the big toe with fanning of the other toes when the lateral sole is stimulated. In adults, the normal plantar reflex is toe curling (flexion), so this upward toe movement indicates an upper motor neuron lesion affecting the corticospinal pathways. The presence of this sign points to UMN pathology such as stroke, multiple sclerosis, or spinal cord or brain injury. In infants, a positive Babinski can be normal due to immature corticospinal tracts, but in adults it’s clinically significant. The other signs described (Kernig, Brudzinski, neck stiffness) relate to meningeal irritation or nuchal rigidity, not the plantar response.