Symmetric Tonic Neck Reflex in Babies – What is it and Steps to Test it

6 min read

Written by Ajanta Biswas

Ajanta Biswas

STNR in Babies

Reflexes are spontaneous and involuntary actions of our body that occur without thinking. They are important for our survival as sometimes we need to act immediately without thinking. Babies are born with some primitive reflexes such as the Moro reflex, rooting reflex, and sucking reflex that helps them to survive immediately after birth. Some reflexes stay for the entire life such as the corneal reflex, the cough reflex, etc. Other reflexes related to development appear and disappear at particular stages of development. Symmetric Tonic Neck Reflex in babies is one such reflex you will notice just before they learn how to crawl.

Symmetric Tonic Neck Reflex or STNR is extremely important for your baby’s motor development. It is important to know about STNR to measure the progress your baby shows from infancy to toddlerhood. This is because a delayed STNR and a retained STNR both can negatively impact the growth of your baby. 

In This Article

What is Symmetric Tonic Neck Reflex in Babies?

STNR or Symmetric Tonic Neck Reflex is the simultaneous movement of bending and stretching of the limbs of the baby with respect to the neck and head movements. In this developmental reflex, the arms of the baby bend and the legs stretch when they move their heads near their chest. On the contrary, their arms stretch and their legs bend when they move their head backward or away from their neck. This reflex helps babies learn to move the upper and lower parts of their body independently of each other.

Symmetric Tonic Neck Reflex is not a primitive reflex. It is a transitional reflex that occurs in babies when they are between 6 to 9 months and disappears during 11 months. The STNR reflex plays a vital role in initiating the major milestone of crawling in your baby. It prepares your baby to move their upper and lower extremities independently but with synchronization. This rhythmic movement of the limbs along with the head is necessary for crawling. That is why this reflex is also termed the crawling reflex.

Causes of Symmetric Tonic Neck Reflex in Babies

STNR Causes

STNR appears naturally when the baby successfully integrates two primitive developmental reflexes

  • Asymmetric Tonic Neck Reflex (ATNR)
  • Tonic Labyrinthine Reflex (TLR)

TLR enables babies to control their necks and heads against gravity, whereas ATNR develops their gross and fine motor skills.

As a result of their successful integration, STNR appears, which takes the motor development of your baby to the next stage.

Symptoms of Symmetric Tonic Neck Reflex in Babies

The symptoms of STNR will appear in your baby between 6 to 9 months. You can confirm that your baby reaches the STNR stage by observing the following symptoms

  • Whenever the neck bends the arms also bend but the legs straighten
  • Whenever the neck and arms straighten the legs lend

For confirming STNR you can do a quick STNR test on your baby.

Testing For STNR in Babies

To test Symmetric Tonic Neck Reflex in your baby you will have to do the following steps

  • Lie your baby on the tummy in your hands with his/her face in the forward direction.
  • Now first gently push your baby’s head down so that it can almost touch the chest.
  • You can notice that the arms of your baby will bend and the legs straighten if your baby has STNR.
  • Then gently push your baby’s head upward i.e. move the chin away from the chest.
  • You will notice now the arms of your baby are straightening and the legs bending.

What is STNR Integration in Babies?

STNR Integration

STNR integration occurs when your baby’s brain develops enough to inhibit this involuntary reflex as a voluntary action.

Generally, STNR integration occurs in babies from 9 to 11 months. After the STNR integration babies will be able to move their arms and legs separately or unitedly according to their will.

You can aid in the SNTR integration by increasing the tummy time for your baby. According to a study published in Pediatrics, tummy time positively impacts gross motor skills and overall development. Placing movable and attractive toys around your baby can also enhance neck and body movement.

[Read : Tummy Time For Babies- A Must Do]

Relationship Between STNR and ATNR

In ATNR or Asymmetric Tonic Neck Reflex, the right hands of babies stretch out and the left hands bend if they turn their head towards the right side and vice versa. ATNR is a primitive reflex that disappears in between 5 to 7 months.

According to a report published in Sage Journals, STNR or Symmetric Tonic Neck Reflex emerges only after the proper integration of the ATNR. Though these two reflexes are distinct from each other their purpose is the same.

Both ATNR and STNR help in developing fine and gross motor skills, direction discrimination ability, and hand-eye coordination in the baby.

What Does Retained STNR Mean?

In general, the Symmetric Tonic Neck Reflex disappears when babies start standing and walking on their own. So STNR should not be present by the time your baby gets one year old.

According to the study published in Europe PMC, in case if a baby has STNR after 12 months then it is termed Retained STNR which indicates delayed motor development that can lead to complications such as

  • Poor balancing and frequent falls during crawling
  • Poor body posture control
  • Direct walking by skipping the crawling part
  • Walking by using both hands and legs

Long-Term Effects of Retained STNR

Some of the long-term side effects of retained STNR are;

  • “W” sitting posture and difficulty in sitting for long
  • Ape like walking
  • Hunched posture of standing
  • Vision disorder
  • Difficulty in reading writing and accomplishing various sensory-motor activities at school
  • Muscle tension in the neck and regular headache
  • Awkward gait

[Read : W-Sitting Position In Children]

When to See a Doctor?

STNR Consulting Doctor

As both the delayed and retained STNR can cause development hazards it will be wise to consult your doctor if you suspect any of them.

You need to see a doctor for SNTR in case

  • Symptoms of SNTR have not appeared in your baby after 9 months
  • Symptoms of SNTR have not disappeared after 12 months
  • The baby is not crawling even after 10 months
  • The baby shows delay in achieving several other developmental milestones
  • The baby shows poor hand-eye coordination and disbalance or awkward posture while walking

So, the Symmetric tonic neck reflex in babies is a vital but temporary reflex that helps them to separately move their upper and lower extremities at a time. Timely integration of this reflex is important for the healthy development of your baby. You can aid in the process of STNR integration by helping your baby to move forward using different attractive tools. Feel free to talk to your doctor about any doubts you have regarding the reflexes in your baby.

[Read : Developmental Delays in Babies]


1. How Long Does The Tonic Neck Reflex Last in Babies?

Generally, tonic neck reflex will last for up to 5 to 7 months in babies. The tonic neck reflex and the Moro reflex can both be present on both sides of the body equally.

2. Is Symmetric Tonic Neck Reflex Beneficial For Babies With Special Needs?

Yes, the Symmetric tonic neck reflex helps your baby to make a transition from the lying position towards the first crawling. However, a retained STNR can indicate a developmental delay and may result in further complications in babies with special needs.

Read Also: Baby is Not Crawling – Causes and Ways to Deal With it

Ajanta Biswas,MA (English)

Studying English literature has been highly instrumental in creating a love for English and World Literature for this writer. Ajanta has been writing for more than two years. She specializes in creating short and crisp blogs that can create awareness among women about healthy pregnancy and among parents about better parenting.Read more.

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