Babinski Reflex

Babinski reflex is one of the normal reflexes in infants.
Babinski reflex occurs after the sole of the foot has been firmly stroked. The big toe then moves upward or toward the top surface of the foot. The other toes fan out.
This reflex is normal in children up to 2 years old. It disappears as the child gets older. It may disappear as early as 12 months.
With the maturation of upper motor neuron pathways the Babinski sign disappears and the great toe goes down on stimulation of the sole.
The sign is generally attributed to a lesion of the pyramidal tract.
Upper motor neuron lesions result from pathology in the cerebral cortex, brainstem, or spinal cord and are signaled by an increase in muscle tone (spasticity), hyperreflexia, and the persistence or reappearance of primitive reflexes, such as the extensor plantar response (Babinski sign).

When the Babinski reflex is present in a child older than 2 years or in an adult, it is often a sign of a CNS disorder. Disorders may include:

It is mediated by the spinal cord, but influenced by higher centers.
The corticospinal tract influences the segmental reflex in the spinal cord.
When the corticospinal tract is not functioning properly, the result is that the receptive field of the normal toe extensor reflex enlarges at the expense of the receptive field for toe flexion. Toe extension is consequently elicited from what is normally the receptive field for toe flexion.
The maintenance of territorial integrity of the receptive fields is apparently one way in which the cortex exerts its influence under normal conditions.
The clinical significance lies in the fact that the abnormal response reliably indicates metabolic or structural abnormality in the corticospinal system upstream from the segmental reflex.

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