Final answer:
The Babinski reflex is normal in infants and usually disappears by 2 years of age as the nervous system matures. In adults, it can signal central nervous system issues like stroke or multiple sclerosis and affects balance and walking.
Step-by-step explanation:
The Babinski reflex is a normal finding in newborn infants and is characterized by dorsiflexion of the foot and extension and splaying of the toes in response to stimulation of the plantar surface. It is normally present at birth due to incomplete myelination in the neuromuscular system.
In most children, the presence of the Babinski sign indicates the immature state of the spinal cord and brain development. The reflex generally disappears as the nervous system matures, typically by the age of 2 years.
The presence of a Babinski sign in adults can be indicative of underlying neurological problems, as it reflects disruptions in the corticospinal tract or cerebral cortex input which is normally responsible for suppressing this reflex.
In adults, presence of the Babinski sign could imply a variety of central nervous system disorders such as stroke, multiple sclerosis, or spinal cord injury. It is because an adult should typically present a negative Babinski sign, indicated by curling of the toes and a moderate plantar flexion, which reflects proper myelination and neuromuscular function.
The Babinski reflex in adults can affect balance and normal walking and can be a sign of upper motor neuron (UMN) disease, such as with the clasp-knife response which is a sudden decrease in resistance following initial tension when a limb is passively flexed or extended.