The Symmetrical Tonic Neck Reflex (STNR) is an involuntary movement pattern that appears during a child’s first year of life. These primitive reflexes are governed by the brainstem. The STNR plays a part in preparing a child for moving onto all fours and eventually crawling. While this reflex is a normal and necessary stage of early development, it should naturally disappear, or integrate, as the brain matures. Determining if this reflex is still present in an older child requires a specific assessment procedure, which acts as a screening tool for possible developmental interference.
The Symmetrical Tonic Neck Reflex (STNR)
The Symmetrical Tonic Neck Reflex typically emerges between six and nine months of age, serving to separate the movement of the upper and lower halves of the body. Its primary function is to help the infant rise up onto their hands and knees, acting as a precursor to crawling. When the head is flexed forward (chin to chest), the reflex causes the arms to bend and the legs to straighten. The opposite occurs when the head is extended (looking up), causing the arms to straighten and the legs to bend.
This reflex is generally short-lived, with full integration expected by nine to twelve months of age. Integration happens as the child engages in advanced motor tasks, like hands-and-knees crawling, which override the involuntary pattern. If the STNR remains active past this timeline, it is considered retained and can interfere with later developmental milestones. Retention can affect visual skills, posture, and coordination, making testing necessary in older children.
Step-by-Step Assessment Procedure
The assessment for a retained STNR involves placing the child in a specific position to elicit the reflex response. Instruct the child to get into the quadruped position (“all fours”) on a comfortable, non-slip surface. Ensure their hands are positioned under their shoulders and their knees are beneath their hips, creating a stable box shape with a flat back.
Once stable, the first movement involves neck flexion, or looking down. Instruct the child to slowly lower their head and tuck their chin toward their chest. The child should hold this position for five to ten seconds while maintaining their body shape. The key is for the child to move their head independently and slowly, without the observer physically moving it.
The second movement is neck extension, or looking up. From the quadruped position, instruct the child to slowly raise their head, looking forward or slightly upward. They should hold this position for five to ten seconds. Throughout both movements, the child should keep their back flat and their hips centered over their knees, focusing on slow and controlled execution.
Identifying Indicators of Retention
A retained STNR is indicated by involuntary physical reactions during the head movements. When the child lowers their head (neck flexion), a positive sign of retention is the involuntary bending or collapsing of the elbows. Other indicators include a visible straightening of the legs or a shifting of the hips backward toward the heels.
Conversely, when the child raises their head (neck extension), the observer should look for the opposite reaction. Signs of a retained reflex include the hips involuntarily bending or shifting backward, or the child attempting to sit back onto their heels. The arms may also straighten and lock out at the elbows. Difficulty maintaining balance, a visible tremor, or a struggle to transition smoothly between positions suggests the reflex may still be active.
Implications and Professional Consultation
The presence of a retained STNR in an older child can manifest as difficulties in various areas of development. Common challenges include poor sitting posture, leading to slumping at a desk, and challenges with near-to-far visual tracking, such as copying information from a whiteboard. The reflex can also contribute to a lack of coordination, W-sitting, or general clumsiness.
This assessment procedure is a screening tool, not a definitive diagnosis. If the screening suggests the reflex is retained, consult with a professional specializing in reflex integration. Occupational therapists, physical therapists, or developmental pediatricians can perform a comprehensive evaluation and confirm the retention. These specialists implement a program of therapeutic exercises designed to help the nervous system fully integrate the reflex.