Final answer:
A positive Babinski sign in a 9-month-old toddler is normal and expected during a neurological exam, indicating proper neuromuscular function at this developmental stage.
Step-by-step explanation:
The presence of a positive Babinski sign in a 9-month-old toddler is considered normal. When performing a neurological exam, the plantar reflex is tested, which may induce the Babinski reflex—a dorsiflexion of the foot with extension and splaying of the toes in response to a stimulus to the sole. During infancy, this is an expected response and indicates proper neuromuscular function. The reflex should be suppressed as the corticospinal tract matures, which usually occurs as the child starts to walk. In adults, the reflex can be problematic as it suggests issues such as reduced myelination of the spinal tract, which could affect balance and muscle control.