What is the Babinski reflex?
The Babinski reflex, or plantar reflex, is afoot reflex that happens naturally in babies and young children until they’re about 6 months to 2 years old. This reflex is usually tested by doctors by stroking the sole of the foot. When the big toe bends up and back toward the top of the foot while the other four toes spread out from one another, it’s called the Babinski sign.
This reflex was first discovered and named by the French neurologist Joseph Babinski. He describes it in a report published in 1896. The Babinski sign has since become an essential tool used by doctors and pediatricians. They use it to make sure that both adult and child brain activity, neurological responses, and nerve activity are normal and don’t indicate any underlying abnormalities in the brain or the nervous system.
This reflex is often tested beside other natural reflexes that babies have during infancy. Other reflex tests include the:
- root reflex, in which the doctor rubs a finger on the corner of the baby’s mouth to see if the baby reflexively moves their head toward the direction of stroking to look for a nipple or bottle to feed on
- suck reflex, in which the doctor touches the roof of the baby’s mouth to see if the baby begins to suck the finger as if feeding on a nipple or bottle
- grasp reflex, in which the doctor rubs a finger on the palm of the baby’s hand to see if the baby reflexively wraps their fingers tightly around the doctor’s finger
Babies don’t have full control over their nervous systems, so these reflexes are common and indicate a healthy neurological function. As children grow, they get better control over their nervous systems. As a result, the Babinski reflex and other common reflexes seen in infancy disappear.
The Babinski reflex may be normal in children up to 2 years old. It can sometimes end after 12 months. If the Babinski sign is still noticeable beyond that, it likely indicates neurological problems. The Babinski reflex is never a normal finding in adults.
How is it tested?
To test the Babinski sign, your doctor will use an object, such as a reflex hammer or a key, to stroke the bottom of your foot from your heel up to your big toe. Your doctor may scrape the object roughly across the bottom of your foot, so you might feel some minor discomfort or a tickle. It takes practice to properly perform the Babinski test, and it may appear falsely positive or negative if not done correctly.
When is a Babinski sign normal?
In a child younger than 2 years old, the big toe should bend up and backward toward the top of your foot while the other four toes fan out. This response is normal and doesn’t indicate any problems or abnormalities.
In a child older than 2 years old or in a mature adult, the Babinski sign should be absent. All five toes should flex, or curl downward as if they’re trying to grab something. If this test is conducted on a child older than 2 or an adult and the toes respond like those of a child under two years old, this can indicate an underlying neurological issue.
When is a Babinski sign abnormal?
In a child under 2 years old born with intellectual disabilities or other mental conditions, the Babinski reflex may be held for an abnormally long period of time. In a child under 1–2 years old born with any condition that causes spasticity (muscle spasms and stiffness), the Babinski reflex may seem weak as the doctor strokes the baby’s foot or may not happen at all.
In adults or children over 2 years old, a positive Babinski sign happens when the big toe bends up and back to the top of the foot and the other toes fan out. This can mean that you may have an underlying nervous system or brain condition that’s causing your reflexes to react abnormally.
Conditions that can affect the Babinski sign
The Babinski reflex indicates a typical neurological function in children under 1–2 years old.
If the Babinski reflex, or a positive Babinski sign, happens in children over 2 or in adults. This can indicate underlying neurological conditions, nervous system disorders, or brain disorders. These include:
- upper motor neuron lesion
- cerebral palsy
- brain injury or brain tumors
- spinal cord tumor or injury
- multiple sclerosis (MS)
Getting a yearly physical for you and your child is the best way to regularly test your reflexes to make sure that your nervous and neurological functions are normal.
If your child is younger than 1 but doesn’t have a normal Babinski reflex, ask your doctor if they should be tested for any underlying neurological conditions. Your doctor may refer your child to a specialist who can examine the brain and nervous system more closely.
Some conditions in children that may cause an abnormal Babinski reflex can’t be cured. These include intellectual disabilities and cerebral palsy. However, you can address these conditions by treating their symptoms early and making appropriate lifestyle choices.
In adults with a positive Babinski sign, more testing for neurological conditions or events such as strokes may be necessary to discern what’s causing the abnormal reflex. In the case of brain injuries, tumors, or other similar conditions, you may need to seek further examination by a specialist. You may also require surgery to address the cause of the abnormal reflex. This can help prevent any complications and ensure that you remain in good health.