What Is the Symmetric Tonic Neck Reflex?

Reflexes are movements that humans do involuntarily, without thinking. You can observe these from the moment your child is born. There are five common reflexes you’ll see in your newborn:

  • Rooting reflex searching for a nipple on a breast or bottle
  • Sucking reflex happens when the roof of the baby's mouth is stimulated
  • Grasping reflex bending the fingers to grab
  • Startle reflex responding to loud noises
  • Tonic reflex — happens when the baby lies on their back

The symmetric tonic neck reflex (STNR) is a reflex that normally appears during your baby’s first year. It typically begins to diminish by the time they reach 9 to 10 months.

The terms "symmetric tonic neck reflex" and "symmetrical tonic neck reflex" mean the same thing. Your pediatrician may use either term.

‌The STNR reflex helps your infant learn to move the top half and the bottom half of their body independently from each other. The symmetric tonic neck reflex is commonly referred to as the “crawling reflex” because it allows your baby to make the transition from laying down to getting up on their hands and knees.

You’ll typically notice your baby going through this stage around 6 to 9 months of age, when they transition from laying on the floor or other surface to crawling.

When your baby has reached the STNR stage, you may notice that when their neck and arms straighten, the legs will bend. When the neck and arms bend, the legs will straighten. These movements are important for crawling and taking their first steps. 

Why Is This Reflex So Important?

The brain, spinal cord, and nerves make up the nervous system, which controls the early motor skills developed during this time. Babies begin to control their movements during this stage.

The symmetrical tonic neck reflex is important for the development of posture, eye-hand coordination, and playing sports. 

What Is a Retained STNR?

The symmetric tonic neck reflex links your baby's head movements to their arm and leg movements. If the baby retains this reflex, it can cause problems as they grow older. Some possible long-term effects of retained STNR are:

  • Headaches from muscle tension in the neck
  • Difficulty writing and reading
  • Difficulty sitting still
  • Vision problems
  • Social and educational delays

Signs of retained STNR include:

  • Poor, hunched posture
  • Skips crawling and go straight to walking
  • “W” sitting, when the knees are in front of the body but the feet are out to the side of the hips
  • "Bear walking" or walking on hands and feet
  • Difficulty copying from a blackboard

Continued

Talking To Your Pediatrician About STNR

Being a parent can be scary and overwhelming. Keep in mind that it is normal for children to develop at different rates. If you are worried about your child’s development, it is always recommended to contact your pediatrician and communicate your concerns. If further steps are needed, your pediatrician will be able to make recommendations and refer you to a specialist, if needed. 

An easy way to test for retained STNR is with a developmental pre-screening questionnaire. This pre-screening tool can be used to track a child’s developmental stages from as early as 1 year. 

The questionnaire can't be used to predict future neurological problems, but can be useful in detecting retained primitive reflexes such as STNR.

WebMD Medical Reference Reviewed by Dan Brennan, MD on April 27, 2021

Sources

SOURCES:

Paediatrica Indonesiana: "Detecting neurodevelopmental problems in children aged 1-5 years using the simple parent-reported screening tool in combination with primitive reflex assessment." 

Pediatric Research: "The Symmetric Tonic Neck Reflex (STNR) as a Normal Finding in Premature Infants Prior to Term."

Rhythmic Movement Training International: "Symmetrical Tonic Neck Reflex (STNR)."

StatPearls: "Primitive Reflexes."

StatPearls: "Tonic Neck Reflex."

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