The Babinski reflex, also known as the plantar reflex, is a primitive reflex that involves a specific response to stimulation of the sole of the foot. It is used in clinical settings to assess the function of the central nervous system, particularly the corticospinal tract, which is responsible for voluntary motor control.
Response
- Normal response in adults: Stroking the lateral side of the sole of the foot with a blunt object typically results in the downward flexion (plantar flexion) of the toes.
- Positive Babinski sign: If the toes extend upward (dorsiflexion of the great toe) and the other toes fan out, it is considered a positive Babinski sign, which may indicate damage or dysfunction of the corticospinal tract.
In infants up to 12-24 months of age, the Babinski reflex is normally present as the corticospinal tract is not yet fully developed.
Clinical Significance
The Babinski reflex is an important neurological examination tool used to evaluate:
- Upper motor neuron lesions: A positive Babinski sign may indicate damage to the corticospinal tract or other parts of the central nervous system. Conditions associated with a positive Babinski reflex include:
- Stroke
- Multiple sclerosis
- Traumatic brain injury
- Amyotrophic lateral sclerosis (ALS)
- Normal development in infants: The reflex is a normal finding in infants due to incomplete myelination of the corticospinal tract.
Testing Procedure
- The patient lies supine or sits with the legs extended.
- The examiner uses the blunt end of an object (e.g., the handle of a reflex hammer) to stroke the sole of the foot.
- The stroke begins at the heel, moves along the lateral side of the foot, and ends near the base of the toes.
- The response of the toes is observed and recorded.
Interpretation
- Positive Babinski sign: Dorsiflexion of the great toe and fanning of other toes.
- Negative Babinski sign: Plantar flexion or no response in the toes.
Historical Context
The reflex is named after Joseph Babinski, a French neurologist who first described it in 1896. His discovery helped differentiate between lesions of the central nervous system and peripheral neuropathies.