Asymmetrical Tonic Neck Reflex (ATNR)

The asymmetrical tonic neck reflex (ATNR), also called the fencing reflex, is a newborn reflex. When your baby turns their head to one side, their arm and leg on that side straighten, and the opposite arm and leg bend. It helps build muscle tone. It also supports early hand-eye coordination.

ATNR plays an important role during birth and early development. It usually fades by about 6 months, as your baby’s brain matures. It allows your baby to start making more controlled movements.

If it doesn’t fade as expected, it may affect movement and learning later in life. Healthcare providers often manage a lasting ATNR with physical therapy or occupational therapy.

What is the purpose of the ATNR?

ATNR is a primitive reflex. This means it’s an automatic movement babies are born with. It begins before birth and supports early growth and development.

In your baby’s first months of life, this helps them move and respond to their surroundings. These movements support their motor system (the part of their brain that controls movement) as they develop.

ATNR may also play a role in hand-eye coordination. When your baby turns their head, the arm on that side straightens, and their hand moves into view. This helps prepare your baby for reaching and other similar movements.

As your baby’s brain develops, higher brain areas take control. The reflex gradually fades. This allows your child to make voluntary movements (actions they choose to make on purpose).

When ATNR disappears, your baby can begin skills like rolling over.

ATNR test

A healthcare provider will check for this at well-baby visits during your child’s first six months. To test for it, they’ll:

• Lay your baby on their back
• Gently turn your baby’s head to one side

A reflex should happen immediately when their head turns. You should see their arm and leg on their face side extend while the opposite limbs flex.

If your baby doesn’t have this primitive reflex, don’t panic. A healthcare provider may run more tests to find out if they lost it already or if something else is causing it.

At what age does the ATNR disappear?

It normally integrates (fades away) within the first six months of life. As your baby’s brain grows, this becomes less active and usually disappears.

You may see it go away as soon as 3 months, but it’s typically gone by 6 to 7 months. In most babies, it’s completely gone by 9 months.

If the ATNR doesn’t fade after 6 to 9 months, your healthcare provider may view it as a sign of a motor development issue that needs a closer look.

What is a retained ATNR?

A retained ATNR means the reflex didn’t fade when it was supposed to. Most babies outgrow it by about 6 months as their brain learns to control movement on purpose. When that doesn’t fully happen, the reflex stays active.

When your baby keeps the reflex, their head can still trigger an automatic arm or body movement. This might make certain skills harder to do, even though it was helpful earlier in life.

A retained reflex may affect daily activities, like:

• Coordinating both sides of their body (walking)
• Crossing the middle (writing across a page)
• Eye tracking (reading)
• Posture or balance (sitting still)

This isn’t about effort or intelligence. A retained reflex may relate to how your child developed early on. It isn’t caused by behavior problems or not trying hard enough.

What conditions are the ATNR associated with?

If it stays active past infancy, it may be a clue about how your child’s nervous system is developing. Research suggests it may show up more often in some children with:

• ADHD
• Autism spectrum disorder
• Cerebral palsy

Providers don’t use this reflex alone to make a diagnosis. Your child may benefit from other tests that take a closer look at their development.

If your child is missing developmental milestones for their age (like sitting or crawling) or their muscle tone seems stiff or floppy, contact their healthcare provider right away.

What are ATNR exercises?

Physical therapy or occupational therapy exercises may help with ATNR retention. Therapy may include activities that build:

• Strength
• Coordination
• Balance
• Crossing the midline

Your child’s therapist will create a plan specific to their needs. Here are a few examples of what these exercises may look like:

• Rocking: You start on your hands and knees. Then, you rock your hips back toward your heels. Next, you rock forward until your shoulders move over your hands. You repeat this movement in a slow, steady way.
• Bear walk: You start on your hands and feet with your knees lifted. You walk forward using your hands and feet. Keep your back flat and move slowly and steadily.
• Rolling like a log: You lie flat on your back with your arms stretched overhead. You roll to one side without twisting your body. Then, you switch directions and repeat.

You may do these exercises in your provider’s office and at home. Your provider will show you how to do them safely. This will help your child avoid injury.