The Asymmetrical Tonic Neck Reflex, or ATNR, is an involuntary movement pattern observed in newborns. It is one of several primitive reflexes present at birth. This reflex is characterized by a specific posture that occurs when a baby lying on its back turns its head to one side. The arm and leg on the side the baby is facing will extend, while the arm and leg on the opposite side will flex, creating a position often called the “fencer’s pose.”
The Role of ATNR in Early Development
The ATNR emerges around 18 weeks in the womb and is active during birth and early infancy. Some evidence suggests this reflex assists the baby during a vaginal delivery, helping the infant move through the birth canal. After birth, the ATNR continues to contribute to development by building muscle tone and coordinating one-sided body movements.
It plays a part in the development of hand-eye coordination, as the reflex prompts the infant to extend an arm into their field of vision when they turn their head. This connection helps lay the groundwork for future motor skills. As an infant’s brain and motor systems mature, the ATNR naturally integrates, or fades, by about six months of age, allowing for more controlled and voluntary movements to develop.
Identifying a Retained ATNR
When the ATNR persists beyond the six-month timeframe, it is called a retained reflex. This retention can affect a child’s motor development and coordination. A common sign is difficulty with skills that require using both sides of the body together, such as crossing the midline—the imaginary line dividing the body in half. This can manifest as an inability to use one hand for a task on the opposite side of the body without turning the entire torso.
Challenges with handwriting and other fine motor skills are also associated with a retained ATNR. The automatic arm extension when the head turns can interfere with holding a pencil and looking at the paper simultaneously, leading to a tight grip and poor letter formation. Visual tracking issues may also arise, as the eyes might have difficulty smoothly crossing a page, causing the child to skip words or lose their place while reading.
Balance and gross motor coordination can be affected as well. Activities like learning to ride a bike or swimming may be more difficult because the fencer pose can disrupt balance when the child turns their head. Another indicator is mixed dominance, where a child does not develop a consistent preference for using their left or right hand, foot, or eye. These persistent reflexes can sometimes point to broader developmental delays.
Strategies for Integration
For children who show signs of a retained ATNR, specific movements and therapeutic activities can encourage the reflex to integrate. These exercises are guided by a professional, such as a pediatric occupational therapist, who can properly assess the child’s needs. The goal is to help the brain and body mature out of the primitive reflex pattern.
Therapists may use specific exercises that mimic early developmental movements. For example, activities like “lizard crawls” or “log rolls,” where the child coordinates their limbs while moving, can help establish new neural pathways. These movements are performed slowly and deliberately to retrain the body’s response to head movements.
Parents with concerns should seek a professional evaluation from a pediatrician or occupational therapist. A trained professional can confirm a retained reflex and rule out other potential causes for a child’s difficulties. They can then create a tailored program of safe and appropriate activities for the child’s situation.