The Babinski reflex or plantar reflex is incorporated into routine neurological examination in order to test the integrity of the corticospinal tract 1. The test does not require sophisticated equipment or active patient participation and can therefore be performed in patients who are otherwise unable to cooperate with a full neurological examination.
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Pathology
The corticospinal tract originates from the cerebral cortex and descends through the brainstem and spinal cord to synapse with alpha neurons of the peripheral nervous system 1. Damage anywhere along the corticospinal tract can result in the presence of the Babinski reflex.
Normally, stimulation of the S1 dermatome on the lateral plantar aspect of the foot results in plantar flexion of the toes 1. Descending fibers of the corticospinal tract normally keep ascending sensory stimulation from spreading to other nerve roots. However, damage to the corticospinal tract results in spread of nociceptive input beyond the S1 anterior horn cells to the L4/5 anterior horn cells and results in contraction of the toe extensor muscles 1.
Technique
Use a dull or blunt instrument to run up the lateral plantar aspect of the foot from the heel to the little toe and across the metatarsal pad to the base of the great toe. If there is extension (upward movement or dorsiflexion) of the great toe with or without fanning of the other toes, Babinski reflex is said to be present. If the toes deviate downward the reflex is absent. If there is no movement this is considered a neutral response and has no clinical significance 1,2.
In infants with an incompletely myelinated corticospinal tract the Babinski reflex may be present up to 24 months of age which is considered normal in the absence of other neurological signs or symptoms 1.
History and etymology
Joseph Babinski, a neurologist born in Paris to a refugee family from Poland first described the Babinski reflex in 1898 3.
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