Asymmetric tonic neck reflex (ATNR) is the term used to describe the typical movement of a newborn turning its head to the side where the arm and leg are also extended at the same time. On the side facing away from the head, however, the limbs bend in contrast. In addition, the fist on the side facing the face tends to be opened, while on the opposite side it usually remains closed. This early childhood reflex is also called the fencer’s stance.
What is the asymmetric tonic neck reflex?
The asymmetric tonic neck reflex begins to be noticeable by the eighteenth week of pregnancy. By the time of birth, this fetal movement increases in intensity. This favors the motor development of the child and the development of muscle strength. Finally, the ATNR, in interaction with other acquired reflexes of the baby, very effectively supports the birth process. The asymmetric tonic neck reflex greatly improves the mobility of the fetus‘ shoulders and hips as it makes its way through the narrow maternal pelvis. In the birth canal, the baby has to turn several times as if on a spiral, and the ATNR is very helpful to it in this process. The reflex is stimulated by pressure on the neck. After birth, the effect of the ATNR gradually weakens. The first abnormalities pass after only four to eight weeks of life. However, if there are difficulties during delivery, such as those resulting from a cesarean section or forceps delivery, inhibition of the asymmetric tonic neck reflex may be delayed. Sometimes it is never completely suppressed in such cases.
Function and Purpose
The newborn cannot move its hands to the center of the body and beyond without effort until the asymmetric tonic neck reflex has been successfully inhibited. For example, it cannot previously bring any object to its mouth with its hands to examine it. Once the ATNR has been largely inhibited, the eyes can also become more independent of the head movements. This is the only way that the baby will later be able to visually hold on to an external object, even if it is in motion itself. However, if the asymmetric tonic neck reflex still determines the baby’s movement patterns after the fourth to sixth month of life, it will increasingly become an obstacle to the infant’s further gross and fine motor development. Turning the head to the side can then continue to result in involuntary stretching of the limbs on the side of the face. Under certain circumstances, the continuing fencer posture is then responsible for the fact that a child cannot turn from his back to his stomach or can do so only with great difficulty, or later cannot learn to crawl properly. In such cases, the bending and stretching of arms and legs continue to be strongly determined by the posture and movement of the head, so that, for example, crossing movements are difficult for the child to perform. It fails to do so because of its own ATN reflexes, which have been dominant for too long.
Illnesses and complaints
The extent to which this deficiency can become entrenched in further development is evident in individual cases even as the child begins school. Such a child, no matter how diligently he or she practices, is unable to keep to the prescribed lines or the left margin when writing. Similarly, problems in guiding the writing instrument, much too strong pressing and difficulties in simple copying exercises can be traced back to the ATNR suffered in early childhood. Reading is also often complicated for children with an unset asymmetric tonic neck reflex, as their eyes can only remain in the respective line of text with more or less difficulty. Thus, individual letters, punctuation marks or even entire words are easily overlooked or the eye suddenly lands on the wrong line. If writing and a head movement such as looking at the blackboard happen at the same time, the writing utensil usually slips down or up. In addition, one of the child’s arms may stretch automatically as soon as he turns his head to look at the blackboard, for example. This reflex will also include unintentional opening of the fingers, which makes handwriting even more difficult. Difficulties in hearing and speaking cannot be ruled out in these cases either. Sometimes perception problems occur in everyday life, especially when planning unfamiliar actions.The early childhood (primitive) reflexes are initially not controlled by the cerebrum and are also only clearly traceable in the first months of the baby’s life. Later, they are gradually suppressed as the cerebrum and especially the frontal lobes develop. If typical early childhood reflexes return in old age, they indicate disturbances in the brain structure, for example in the case of dementia. The reflexes appear at a certain age of maturity of the child and disappear again as if according to a timetable. Accordingly, a premature baby shows different reflexes than a term baby. The disappearance of reflexes is the prerequisite for a child to internalize and learn elementary movements. For example, a baby’s so-called foot-grasp reflex must first regress before it can later acquire the skills of standing and walking. If the reflexes remain formative for a child, doctors can intervene with relatively simple therapeutic means. Training the child’s head movements is often sufficient for this purpose.
