Symmetry and the ATNR Reflex
Symmetry is important!
There is a primitive reflex known as the ATNR reflex (asymmetrical tonic neck reflex) which is present as a newborn and disappears around 6 months of age. In some cases, however, this reflex can be stubborn to integrate and impact a baby’s symmetry as they develop in their gross motor skills. Causes for a retained ATNR reflex include birth trauma, Cesarean sections, pre-natal drugs or alcohol exposure, skipping milestones, a lack of tummy time play and/or excessive time spent in containers such as bouncers and swings which limit developmental exploration and movement.
This ATNR reflex is initiated by neck rotation. If your baby looks to their left, their left arm will extend and their right elbow will bend. If your baby looks to their right, their right arm will extend and their left arm will bend. This reflex is also known as the “fencing” reflex.
When an ATNR reflex is retained, it can impact rolling, cross midline reaching, transitions, crawling and quadruped creeping as an infant. As your child grows, retention of this reflex can lead to problems reading and writing, paying attention, visually tracking, differentiating between right and left sides of the body, and cause difficulties with balance and coordination for activities such as riding a bicycle or throwing and catching.
Consult your Pediatrician or reach out to a Physical Therapist if you have any concerns with a retained ATNR reflex past 6 months of age. Torticollis is one common diagnoses that that can result in retained ATNR reflex.
Left ATNR pictured (baby looking left resulting in right elbow bend and left arm extended)