Babinski's reflex occurs when the great toe flexes toward the top of the foot and the other toes fan out after the sole of the foot has been firmly stroked. This is normal in younger children, but abnormal after the age of 2.

Reflexes are specific, predictable, involuntary responses to a particular type of stimulation.

Babinski's reflex is one of the infantile reflexes. It is normal in children up to 2 years old, but it disappears as the child ages and the nervous system becomes more developed. It may disappear as early as 12 months.

In people more than 2 years old, the presence of a Babinski's reflex indicates damage to the nerve paths connecting the spinal cord and the brain (the corticospinal tract). Because this tract is right-sided and left-sided, a Babinski's reflex can occur on one side or on both sides.

An abnormal Babinski's reflex can be temporary or permanent.

• Generalized tonic-clonic seizure (there may be a temporary Babinski's reflex for a short time after a seizure)
• Amyotrophic lateral sclerosis
• Brain tumor (if it occurs in the corticospinal tract or the cerebellum)
• Familial periodic paralysis
• Friedreich's ataxia
• Head injury
• Hepatic encephalopathy
• Meningitis
• Multiple sclerosis
• Pernicious anemia
• Poliomyelitis (some forms)
• Rabies
• Spinal cord injury
• Spinal cord tumor
• Stroke
• Syringomyelia
• Tuberculosis (when it affects the spine)

Typically, a person (older than an infant) who has a Babinski's reflex will also have incoordination, weakness, and difficulty with muscle control. Safety is important to prevent the risk of injury. The person may need assistance with activity, and the environment should be kept free of hazards.