Synonyms

Long tract sign; Plantar reflex; Upper motor neuron sign

Definition

The Babinski reflex is a component of the neurological exam, used to assess the adequacy of the pyramidal tract (upper motor neuron). This reflex is elicited by making contact along the lateral side of the plantar foot with a blunt implement and not causing pain, discomfort, or injury to the skin; the implement is run from the heel along a curve to the metatarsal pads. There are three responses possible:

  • Extensor (positive or pathological): hallux (great toe) extension and the other toes abduct (fanning)

  • Flexor (negative or normal): all toes flex and the foot everts

  • Indifferent: no response

Current Knowledge

An extensor (positive) response signifies pathology in the upper motor neuron pathways, either in the spinal cord and/or brain, such as in multiple sclerosis, stroke, traumatic brain injury, or spinal cord injury. It may be the sole sign of upper motor neuron damage and is the most popular reflex for evaluation of these pathways for the lower limbs. All infants exhibit an extensor response from birth, which converts to a flexor response during ages 12–18 months as the nervous system matures given normal development; developmental delay may result in a persistent positive response. Indifferent responses may be found in normal individuals but may also indicate the presence of a lower motor neuron or other peripheral nervous system injury that interferes with the expression of a normal flexor response.

Cross-References