Concept
The plantar reflex is a reflex elicited when the sole of the foot is stimulated with a blunt instrument. The reflex can take one of two forms. In healthy adults, the plantar reflex causes a downward response of the hallux (flexion). An upward response (extension) of the hallux is known as the Babinski response or Babinski sign, named after the neurologist Joseph Babinski. The presence of the Babinski sign can identify disease of the spinal cord and brain in adults, and also exists as a primitive reflex in infants. While first described in the medical literature by Babinski in 1896, the reflex has been identified in art at least as early as Botticelli's Virgin and Child with an Angel, painted in the mid-15th century. The lateral side of the sole of the foot is rubbed with a blunt instrument or device so as not to cause pain, discomfort, or injury to the skin; the instrument is run from the heel along a curve to the toes (metatarsal pads). Many reflex hammers taper at the end of the handle to a point which was used for testing the plantar response in the past; due to the tightening of infection control regulation this is no longer recommended. Either a single use device or the thumb nail should be used. There are three responses possible: Flexor: the toes curve down and inwards, and the foot inverts; this is the response seen in healthy adults. Indifferent: there is no response. Extensor: the hallux dorsiflexes, and the other toes fan out. If elicited in an adult, it indicates damage to the central nervous system, but it is a normal reflex in infants (see below). It is also known as the Babinski Sign. As the lesion responsible for the sign expands, so does the area from which the afferent Babinski response may be elicited. The Babinski response is also normal while asleep and after a long period of walking. The Babinski sign can indicate upper motor neuron lesion constituting damage to the corticospinal tract.
