Which statement best reflects the involvement of the corticospinal tract in a positive Babinski sign?

• A. It represents a normal reflex
• B. It indicates peripheral neuropathy
• C. It indicates upper motor neuron pathway dysfunction
• D. It is unrelated to motor pathways

Answer: (C)

The positive Babinski sign points to dysfunction of the corticospinal tract, the primary upper motor neuron pathway for voluntary movement. The corticospinal tract begins in the motor cortex, crosses at the medullary pyramids, and travels down the spinal cord to modulate spinal reflexes. When this pathway is damaged, inhibitory control over the plantar reflex is lost, so stimulation of the sole causes the big toe to extend and the other toes to fan—an upward (Babinski) response. In adults, this is an abnormal sign and indicates an upper motor neuron lesion; in infants it can be normal due to immature myelination. Peripheral neuropathies affect the nerves outside the CNS and typically do not produce a Babinski sign, and the sign is directly related to motor pathways, not unrelated to them.