The Babinski sign is when the big toe moves upwards instead of downwards when plantar flexion, pointing toes, is happening.  Also known as the Plantar Flex, this reflex test has become very prominent in standard neurological examinations.  This test is used to determine the strength of the Corticospinal Tract.  The CST is a pathway in which motor signals are sent from the brain to the lower motor neurons, also known as a descending fiber tract that starts in the cerebral cortex, the outer layer of the cerebrum,  and goes through the brainstem and spinal cord.  Damage anywhere on the CST can determine the presence of the Babinski sign.
