What Is Asymmetric Tonic Neck Reflex (ATNR) in Newborns?

Medically Reviewed by Renee A. Alli, MD on July 04, 2023
3 min read

Asymmetric tonic neck reflex, or ATNR, is one of the primitive reflexes that babies experience as part of brain development. These reflexes are crucial because they help your baby to survive and thrive. 

ATNR should only occur during the first few months after birth without any sequential order. Afterward, new types of reflexes called postural reflexes develop. These latter reflexes are more mature and help in coordination, balance control, and sensory-motor development.

ATNR presents as consistent, one-sided movements of the body that go together with proper hand-eye harmonization. This ''fencer’s pose'' is a motion where your baby appears to be challenging an opponent. The head turns to one side, with the arm and leg on the corresponding side extended or flexed in the air. The opposite limbs flex or curl inward.

A baby begins experiencing ATNR while still in the womb, and this reflex can start as early as 18 weeks into your pregnancy. It’s an important type of reflex that helps your baby move through the birth canal during vaginal birth.

Sometimes, primitive reflexes, including ATNR, can continue beyond their expected timelines. The usual timeframe for ATNR is usually between five to seven months when your child is learning complex motor skills like sitting up.

However, in some cases, your baby may need a year for ATNR to fully integrate. Full integration means that when your baby is awake, they will not show the fencer’s pose when they turn their head lying down.

In some babies, the asymmetric tonic neck reflex doesn’t integrate correctly. This means that they still show signs of the reflex past the usual timeline. Experts associate this with delays in development, but research around this issue is still in its early stages. The condition is known as retained ATNR.

Another vital factor that contributes to retained ATNR is the birth process. A traumatic birth process or birth through a C-section can lead to the condition. Other causes of retained reflexes, including ATNR, are:

  • Head trauma
  • Vertebral dislocation
  • Chronic ear infections
  • Delayed or skipped crawling and creeping
  • Lack of tummy time
  • Falls

Retained ATNR can cause some difficulties for your child. It becomes hard for them to cross the midline of their bodies, for example, and they can't handle objects with both hands. In other instances, the child can't identify which hand or leg to use, causing him to hesitate in movements.

When the choice doesn’t come automatically, the child makes very conscious moves, which can be confusing. Proper ATNR integration is crucial for good visual development as well. 

When it doesn’t happen, your child can’t track a horizontally passing object past the nose without stopping at the midline. This will affect their reading, spelling, and writing abilities later in life. The child might also experience:

  • Poor balance control when they move the head from side to side
  • Poor eye movements
  • Difficulty crossing an imaginary midline
  • The interchangeable use of left and right hands or mixed laterality
  • Poor handwriting
  • Difficulty changing their focus from far to near
  • Inhibited expression of ideas on paper
  • Difficulty in learning to ride a bike
  • Difficulty throwing a ball or catching it
  • Learning problems
  • Inability to multitask

Your child may also show some characteristics similar to ADD and ADHD but this theory needs more research.

Doctors may test for the atypical presentation of retained ATNR if a baby can’t maintain balance. Another reason this warrants a test is troubled visual tracking. Older children may also show some of the signs and symptoms of retained ATNR discussed above.

If you have concerns about the developmental progress of your child, talk to your child's pediatrician. Depending on your child's condition and progress, they may recommend evaluation by an occupational therapist, physical therapist, or neurologist.

After evaluation, the therapist will work with your child to create movements to help integrate ATNR. These movements mimic the early reflex movements and include simple games, exercises, and age-appropriate activities. The aim is to create new learned neural pathways to help with ATNR integration.

Your child's pediatrician will continue to  explore several potential treatment options for the signs and symptoms your child shows. This will help you and your child manage the condition.