The asymmetrical tonic neck reflex is a very important reflex in the first year of life. It helps with everything from getting out of the womb, to rolling, crawling, to developing hand eye coordination. It also plays a vital part in balance, walking and developing cross body movements that help us connect the right and left sides of our body together.
It helps us to reflexively develop eye movement independent of head movements, or the ability to use your eyes without your head moving. It also helps us to create head movements independent of body movements, or the ability to turn our head without our body moving. It helps us to use both sides of our body together through reflexive movements!
If this reflex doesn’t develop appropriately there are very common dysfunctions that result:
- lack of motor skills early in life: Difficulties rolling both ways, difficulties army crawling, and delays in crawling and walking.
- Difficulties with fine motor skills: tying shoes and handwritting
- Difficulties in gross motor skills: hard time learning to ride a bike, difficulties learning front stroke when swimming, seem to lose balance easy and falls often.
- Learning difficulties: Tend to have eye tracking horizontally which creates issues that affect reading skills, often skip words, or lines.
The asymmetrical tonic neck reflex is the most common primitive reflex you will see in clinical practice. This reflex is by far the most common reason for abnormal neurological development that I see in practice!
Prior to 6 months you see this reflex by laying a infant of their back and watching them. When the infant turns their head to one side you will see them straighten their arm and leg on the same side, and flex their arm and leg on the opposite side. This is known as the fencer position and is seen in all infants. The purpose of this is so they start to build their neck muscles, arms muscles, and leg muscles reflexively. It also helps them to start to connect their vision with the extremities! This video is a good example of this reflex in action. https://www.youtube.com/watch?v=0oI_yGQViXY
During this action the child is also developing hand eye coordination and ocular development. When the child’s head moves to the right their eyes move with their head. At this point where the child’s head goes their eyes go, this helps them to learn to use their eyes with their hands. At the same time that the head and eyes move their arm also straightens into their visual field to help them make that connection (this also becomes important if the reflex doesn’t go away on time. It created a scenario where an older child’s eyes still track where their head does, and they don’t develop the ability to use their eyes opposite their head. This can create massive issues with attention and focus. example eye inability to use eyes independent of head movements: https://vimeo.com/335295967/5937b84811 )
Prior to 6 months this reflex also plays a vital role in learning how to roll from, front to back and back to front. The reflective action of arm and leg extension and flexion help them to develop the rolling mechanism. If this reflex doesn’t develop well, rolling is delayed.
To develop crawling appropriately, whether this is army crawling on belly or crawling on all fours the child’s Asymmetrical tonic neck reflex must be inhibited to do it efficiently. Lack of proper development leads to delays in this. The reason why this needs to go away is simple, to create a proper crawling mechanism you need to be able to extend your arm and leg on the opposite side of head rotation. What we have learned prior that is this is that if the reflex doesn’t develop correctly they will flex their arm on the opposite side of head rotation. If this happens a child’s arm will flex or collapse on them with head rotation as they try to crawl.
At about 6 to 8 months the ATNR should be fully developed and at this point go away. This opens up the ability for the child to learn more complex movements strategies without the reflex being in the way. It will allow them to develop crawling appropriately, walking appropriately and be able to maintain balance better, develop hand eye coordination, and much more. The problem is that in many kids that struggle with reflex never goes away!
If this reflex doesn’t go away the most common symptoms you see in kids: Delays in rolling, army crawling, cross crawling, early or late walking, difficulties with balance, difficulties learning to ride a bike, difficulties with fine motor skills like writing and tying shoes, difficulty with reading.
The reason why these symptoms happen is because the reflex is in the way of developing the ability to use your eyes efficiently, use your head opposite your body without movement, and reflexively creates movements of the body. for example, when it comes to riding a bike you need to be able to keep your hands on the handlebars and your arms stable to keep the front wheel straight. If every time you move your head or eyes (which is constant during riding, I.E. looking for traffic) your arms reflexively move and you will have a very hard time staying balanced. This is why it is important that this reflex goes away to allow for new movement patterns to open up!
Link to video for testing ATNR Reflex : https://vimeo.com/395251949
Example of abnormal Reflex and associated eye tracking difficulties Pre and Post: https://vimeo.com/322934108