The Babinski reflex is also known as Babinski’s sign or hallucal dorsiflexion reflex, and was first described by Dr. Joseph Francois Felix Babinski (1857–1932), a French neurologist. The reflex is a neuromuscular one elicited by drawing a blunt point (such as a thumbnail or the end of the handle of a reflex hammer) along the outer sole of the foot from the heel to the metatarsal pads and then toward the great toe (hallux). This should be done with light pressure; a painful stimulus is incorrect. The normal (negative) response is downward extension of the great toe and often other toes, often with extension of the ankle. Abnormal (positive) responses include upward flexion of the great toe, fanning of the toes, upward flexion of the ankle, and flexion of the knee and hip. Some or all of these may be present. This is a superficial reflex, mediated by nerves from the fourth lumbar through the first or second sacral segments and involves activation of the tibial nerve. In the absence of tibial nerve palsy, a positive response indicates dysfunction of pyramidal tract motor neurons in the cortex and subcortex, brain stem, and spinal cord.
Babinski’s sign is one of a group of primitive reflexes, also known as infantile reflexes. These are present at birth but are normally suppressed by higher neural functions as growth and development proceed. The abnormal upgoing response of the toes or an absence of response may be seen in newborns and infants, but the normal response should emerge permanently by the age of 2 years. Other primitive reflexes include the snout reflex, sucking reflex, and grasp reflex, which, when seen in older children and adults, are indicative of significant cortical neurological dysfunction.
Abnormal Babinski responses may be present in meningitis, head or spinal cord injury, brain tumor, spinal tuberculosis (Potts’ disease), hepatic encephalopathy, stroke, amyotrophic lateral sclerosis, multiple sclerosis, some forms of poliomyelitis, and other, less common diseases.
References:
- Mother & Child Glossary. (n.d.). Innate neonate capacities. Retrieved from http://www.hon.ch/Dossier/MotherChild/postnatal/reflexes.html