Tonic Neck Reflex in Babies

Sometimes you might see when your newborn is lying on their back, they often look like they have assumed the position of a fencer who is ready for swordplay. They might have their head turned to the same side as their outstretched arm and their arm slightly bent at their elbow. Sometimes this position would resemble a little archer as if the extended arm of the archer is holding a bow and the bent arm is pulling back the bowstring that is loaded with an arrow. This is the tonic neck reflex. Read further to explore more about the tonic neck reflex.

Tonic Neck Reflex in Babies:

Reflexes are involuntary movements, which are spontaneous and occur as a part of normal activity in babies. Doctors check reflexes for determining if the nervous system and the brain of the baby are working properly. Certain reflexes occur only in specific periods of the baby’s development and they are normal reflexes seen in newborns.

The tonic neck reflex is usually known as the fencing reflex. When your infant is lying down and their head is turned to the left or right, their corresponding arm extends while the other arm bends just next to the head. This looks like they are about to begin fencing.

Primitive reflexes are automatic motor patterns and reactions that emerge during fetal life until after childbirth and are important for the survival of an infant. These primitive reflexes are being integrated and gradually replaced in term infants into higher-level righting, protective, and support postural reactions.(1)

The tonic reflex is one of the crucial reflexes seen in newborns. This reflex begins about 18 weeks after conception. Yes, the associated movements in the infant begin in the womb. This is one of the most important primitive reflexes and it lasts until your newborn is around 5-7 months old.

It is thought that during birth, this tonic neck reflex helps the babies make their way down the birth canal. Following birth, this reflex might help the newborn to discover their hands and also develop hand-eye coordination.

More About Tonic Neck Reflex in Babies And Its Terminology:

The tonic neck reflex or TNR is also known as the Asymmetrical tonic neck reflex or ATNR. There is also STNR or a Symmetrical tonic neck reflex, which is seen later in infancy.

ATNR or Asymmetrical tonic neck reflex appears 18 weeks in utero, and most prominent between 1-4 months of age. It disappears by 5-7 months or a maximum of 9 months after childbirth. ATNR or Asymmetrical tonic neck reflex is produced by rotating the head of the baby to one side, resulting in the ipsilateral extension of the extremities towards which the face is turned and also the contralateral flexion of their extremities. ATNR or Asymmetrical tonic neck reflex is important for postural tone and stability, fine and gross movements, eye tracking, and midline crossing that is important for reading, left-right discrimination, telling the time, and so on.

However, STNR or Symmetrical tonic neck reflex appears 6-9 months after a baby’s birth and lasts until 9-11 months of their age. This specific reflex is elicited by passively moving the baby’s head up and down with subsequent upper extremity flexion and lower extremity extension along with neck flexion. Neck extension produces the extension of the upper extremity and lower extremity flexion. STNR or Symmetrical tonic neck reflex is essential for eye-hand coordination, posture, and focus that is required in various activities like swimming, sitting, playing with a ball, and so on.(2,3,4,5,6)

Observing The Tonic Neck Reflex In Your Baby:

To observe the tonic neck reflex in your baby, put your baby on their back and turn their head gently so that their face is looking left. When tonic neck reflex happens, the baby’s left arm would reach out straight and their right arm would flex next to their head.

Turn your baby’s head gently so that their face is looking right, and their right arm would extend and their left arm would flex.

We must say not to worry if you do not see your baby react with The tonic reflex always. This can depend on how your baby is or whether they are distracted by something else that might be going on in the room.

Some Other Primitive Reflexes Seen in Babies:

Along with the tonic neck reflex, there are some other primitive reflexes seen in babies. Let’s see some of them below.

Rooting Reflexes:

Rooting reflexes begin when the corner of the mouth of a baby is touched or stroked. The baby turns their head and open their mouth and root in the direction of the stroking. This rooting reflex helps the baby find the breast or their feeding bottle to start feeding. The rooting reflex lasts about 4 months after birth.

Suck Reflex:

Rooting helps the infant ready to suck. When we touch the roof of the newborn’s mouth, they begin to suck. Suck reflex does not start until around the 32nd week of pregnancy and it takes until 36 weeks to fully develop. This is why premature babies might have an immature or weak sucking ability. Since babies also have a hand-to-mouth reflex that continues with rooting and sucking, they might suck their hands or fingers.

Parachute Reflex:

Parachute reflex is another primitive reflex seen in babies. Quickly and gently rotate an upright baby to face forward and down to stimulate falling. On this, they would extend their arms. This is the parachute reflex.

Moro Reflex:

This reflex is most often known as a Startle reflex. This is because the Moro reflex usually occurs when a baby is startled by a loud sound or movement. With the loud sound, babies respond by throwing their head, extending out their legs and arms, crying, and then pulling their legs and arms back. A baby’s cry can startle them and trigger this startle or Moro reflex. This reflex is known to last until the infant is about 2 months of age.

Stepping Reflex:

The Stepping reflex is also called the dance or walking reflex because the babies appear to take a few steps or dance when they are held upright with their feet touching the ground. The Stepping reflex lasts about 2 months.

Grasp Reflex:

When you stroke your baby’s palm, it causes the baby to close their fingers in a grasp. This is the grasp reflex. This reflex lasts until the newborn is about 5-6 months of age. A similar grasp reflex is also seen in their toes and this lasts until 9-12 months.

Conclusion:

So, the tonic neck reflex is one of the noticeable primitive reflexes which usually disappears by 5 to 7 months of age in babies. The absence of some primitive reflexes in your child’s newborn stages or their persistence for long could be one of the signs of a neurological problem. However, it is not always the case. If you have any doubt regarding the newborn’s development, you should check with your pediatrician.

References:

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