In our last article, we discussed the term reflex and what it means to still have primitive reflexes after they should have been integrated. This month, we are going to take a look at one of those reflexes, known as the asymmetrical tonic neck reflex, or ATNR.
When the ATNR is elicited, it has an effect on the child’s muscle tone. When the child’s head is turned to the left, the influence on tone causes the right arm to bend and the left arm to straighten. When the child’s head is turned to the right, the influence on tone causes the left arm to bend and the right arm to straighten. This unconscious position assumed by the child provides the reflex with its nickname – the “fencing reflex”.
The ATNR emerges in utero at around 18 weeks, providing stimulation for developing muscle tone as well as the vestibular system while the baby is in the womb. The ATNR is a precursor to eye-hand coordination in an infant. At the latest, it should be integrated by 6 months of age. Generally, the ATNR is assisted in integration when your child is crawling while looking around at toys and objects in their surrounding environment. Children who crawl without simultaneously looking to the left or the right may have more difficulty integrating their ATNR.
If the ATNR is not fully integrated, but remains present in our children, the following difficulties may occur. In younger infants, the presence of the ATNR may make rolling over difficult as the child’s arm will straighten when he looks in the direction he wishes to roll. Rolling is important in order to progress to the next important developmental milestone – crawling. Therefore, with a rolling delay, a delay in crawling may also be noted. Further gross motor implications include eye-hand coordination, such as throwing and catching objects, and bilateral coordination – activities where both hands are used simultaneously to perform a certain task.
In less severe cases where the presence of the reflex is not as noticeable, the reflex may remain unintegrated in a child into their school years. This will have a negative effect on reading and writing abilities. When the child looks in a different direction (such as on the blackboard or to a friend) may cause a small shift in the arm, causing the child to lose their place when reading if they are finger tracking, or causing their writing hand to move slightly during copying and writing. The reflex also causes the child’s hand to want to open, making writing endurance difficult and having a negative impact on their overall quality of work.
Identification of this reflex is thus very important, as sometimes the effect of the reflex may be so slight that it is difficult to pick up. A comprehensive occupational therapy assessment tests for the presence of an ATNR. This is done by getting the child to kneel on all fours with their head in neutral position. If their head is turned to one side and their opposite arm bends then the ATNR is not yet integrated and needs to be addressed.
Luckily, integration of this reflex is still possible with a little work. In order for the reflex to disappear, we need to break the natural and unconscious pattern that takes place. This means that when the child’s head is turned to one side, we need to try and ensure that the opposite arm remains straight during the same activity, and that the arm in the direction to which the head is turned is required to bend. This can be achieved through activities over a roller or leaning over the edge of the bed, requiring the child to support their body weight with their arms while working. Playing on all fours or crawling on the floor while looking at surrounding stimuli is also a good way to integrate the ATNR.
In summary, the asymmetrical tonic neck reflex is naturally found in infants up until the age of 6 months. It results in involuntary movement when the head is turned to either side, causing straightening of the arm in the direction which the head is turned, and bending of the opposite arm. If not integrated, it can have a negative effect on gross motor skills as well as skills necessary for reading and writing. Integrating of the reflex involves activities where the child is encouraged to support their body on outstretched arms while playing and looking at their surrounding environment.
I hope this article offers some understanding on this primitive reflex and the implications it can have if it is still present in your child, even if the presence is slight. Remember, integration of this reflex is still possible through the use of occupational therapy and home activities. Keep an eye out for our next articles where more primitive reflexes will be discussed.