Primitive reflexes are involuntary movement patterns present in infancy, controlled by the brainstem. They are fundamental for early development, serving as building blocks for complex motor skills and cognitive functions. The Symmetrical Tonic Neck Reflex (STNR) is a temporary, yet functionally significant, reflex that appears during this early developmental window.
Defining the Symmetrical Tonic Neck Reflex
The Symmetrical Tonic Neck Reflex (STNR) coordinates the body’s upper and lower halves in response to head position, linking the movement of the neck to the arms and legs. When the head extends (looking upward), the arms straighten and the legs bend. Conversely, when the head flexes downward, the arms bend and the legs straighten.
The STNR is sometimes called the “crawling reflex” because it helps the baby transition from lying flat to the hands-and-knees position. This mechanical coupling facilitates initial lifting and rocking movements. As a transitional reflex, the STNR must integrate, or disappear, to allow for the next stage of movement.
The Normal Developmental Timeline
The STNR typically emerges between six and nine months of age, coinciding with the infant preparing for mobility. This timing is significant because it provides the initial mechanical link needed for the baby to gain strength and coordination to hold themselves up on all fours (the quadruped position).
This reflex is short-lived and should integrate, or be superseded by voluntary control, by nine to twelve months of age. Integration breaks the automatic link between the head and the limbs. This allows the infant to engage in true cross-pattern creeping or crawling, where the head moves freely while the limbs move independently.
Observable Signs of a Retained STNR
If the STNR does not integrate, it is considered retained and can manifest as motor and learning difficulties in older children. The persistent mechanical link makes it challenging to maintain a stable posture, especially when the head moves. This often results in a tendency to slump when sitting at a desk, as the body fights the automatic urge to bend the arms or legs.
Children with a retained STNR may exhibit poor hand-eye coordination, particularly when copying from a vertical surface. Looking up causes the arms to straighten, and looking down causes them to bend, interfering with writing ability. This constant, involuntary muscle tension can also contribute to headaches and neck discomfort.
Early signs of a retained STNR include skipping the cross-pattern crawling phase or using atypical locomotion patterns like “bunny hopping” or bottom-shuffling. Children may also adopt a “W” sitting position, which provides a stable base countering the reflex’s pull. Difficulties are common in tasks requiring simultaneous separation of head and limb movement, such as messy eating or learning coordinated swimming strokes.
Strategies for Integration and Support
Addressing a retained STNR involves targeted, repetitive movement activities that mimic the developmental stages necessary for integration. These movements consciously practice separating head and limb movements, helping the central nervous system establish mature patterns. A common exercise is the Cat-Cow yoga pose, which involves rocking on hands and knees while alternating between flexing and extending the head and spine.
Parents should consult professionals specializing in neurodevelopmental movement or primitive reflex integration. Pediatric Occupational Therapists (OTs) and Developmental Optometrists are often best equipped to assess for a retained STNR and create an individualized program. These professionals guide the child through specific exercises, such as rocking on all fours or crawling, to help the reflex integrate fully.
The goal of integration strategies is to provide the nervous system with the sensory and motor experience missed during infancy. Consistent, daily practice of these specialized movements is often recommended over a period of time. This systematic approach helps the child’s posture, coordination, and learning abilities mature by resolving the foundational developmental challenge.