The Babinski Test is used to detect which condition?

• A. Lower motor neuron lesion
• B. SI joint dysfunction
• C. Pubic symphysis instability
• D. Upper motor neuron lesion

Answer: (D)

The main idea being tested is the integrity of the upper motor neuron pathway, specifically the corticospinal tract. The Babinski reflex assesses how the brain’s inhibitory control over spinal reflex circuits influences the plantar response. When the sole is stroked, a normal adult reaction is toe curling. A positive Babinski sign—dorsiflexion of the big toe with the other toes spreading—signals loss of inhibitory input from the brain to the spinal cord, which points to an upper motor neuron lesion such as stroke or spinal cord injury above the level where the corticospinal tract decussates. This is not something produced by issues like SI joint dysfunction or pubic symphysis instability, which are pelvic joint problems and do not involve the corticospinal tract in producing this specific sign. Lower motor neuron lesions typically present with muscle weakness and atrophy without the extensor toe response, and in adults the Babinski sign is not expected. (In infants, the sign can be normal due to immature nervous system development.)