Primitive reflexes are involuntary, automatic movements present at birth, designed to help infants survive and develop. These movements originate in the brainstem and are not consciously controlled. The Symmetrical Tonic Neck Reflex (STNR) is one such reflex, playing a role in a baby’s early physical development.
Understanding the Symmetrical Tonic Neck Reflex
The Symmetrical Tonic Neck Reflex emerges around six to nine months of age, bridging the earlier Asymmetrical Tonic Neck Reflex and independent crawling. This reflex involves specific body movements in response to head position changes. When an infant’s head bends forward, their arms flex while their legs extend. Conversely, when the head bends backward, the arms extend and the legs flex.
This reflex facilitates a baby’s ability to push up onto their hands and knees from a prone position, a precursor to crawling. The STNR integrates, or disappears, by approximately nine to eleven months of age, allowing more complex motor patterns to emerge. If these reflex patterns persist beyond this typical developmental window, the reflex is considered retained.
Role in Development
The Symmetrical Tonic Neck Reflex serves a distinct purpose in an infant’s motor progression, particularly in the transition from early crawling to upright movement. It helps the baby develop the ability to separate upper and lower body movements, a foundational skill for coordinated actions. The reflex also supports bilateral coordination, enabling both sides of the body to work together.
The STNR contributes to the maturation of the child’s visual and vestibular systems. As the head moves, the eyes are encouraged to track and adjust, enhancing visual perception and balance. This integrated development of motor skills, coordination, and sensory systems prepares the child for more advanced physical activities. The reflex helps develop muscle tone in the neck, shoulders, and back, which is beneficial for maintaining an upright posture.
Signs of Retention
When the Symmetrical Tonic Neck Reflex remains active past its expected integration period, it can present various developmental challenges. One common indicator is a slumped or “W-sitting” posture, where the child sits with knees bent and feet outside their hips, often due to difficulty maintaining an upright position. Children may also struggle with tasks requiring hand-eye coordination, such as catching a ball or copying from a whiteboard.
Difficulties with swimming, particularly the “doggy paddle” stroke, can also be observed, as simultaneous bending of arms and straightening of legs can be challenging. A retained STNR can affect academic performance, manifesting as challenges with attention and concentration, often appearing restless or fidgety when sitting at a desk. Reading and writing can become laborious due to difficulties with visual tracking, as the reflex can interfere with the ability to smoothly move the eyes across a page.
Addressing Retained STNR
Addressing a retained Symmetrical Tonic Neck Reflex involves specific exercises and activities designed to help the nervous system complete its developmental process. These interventions are guided by professionals such as occupational or physical therapists specializing in neurodevelopmental techniques. The exercises mimic the movements associated with the reflex in a controlled manner, gradually helping the nervous system integrate the pattern. Early identification of a retained STNR allows for timely intervention, which can significantly support a child’s overall development and alleviate associated challenges.