The primitive reflexes of the newborn are the reflexes that the neonates perform involuntarily. In the medical literature, in addition to primitive reflex, a great variety of terms have also been used: primary neonatal reflexes, reflexes of development, reflexes and infantile reactions or automatisms (García-Alix and Quero, 2012).
Some movements are spontaneous, which are presented as part of the habitual behavioral repertoire of the baby. On the other hand, reflexes also occur in response to certain stimuli (University of Rochester Medical Center, 2016).
Reflexes are one of the essential components in physical and neurological examinations, since their abnormal presentation or absence can be an indicator of a possible compromise in the nervous system (University of Rochester Medical Center, 2016).
Primitive Reflections of the Newborn
On the other hand, we must bear in mind that some reflexes have a transitory component , some types will only be presented at specific periods of child development(University of Rochester Medical Center, 2016).
What are primitive reflexes?
With the term primitive reflex we refer to a set of very stereotyped motor responses triggered spontaneously or to specific stimuli that are part of the normal motor behavior of babies (García-Alix and Quero, 2012).
The great part of these motor responses appear during the second half of the gestation period and will be present in the postnatal stage (García-Alix and Quero, 2012).
All the variety of involuntary movements will allow the baby: develop the motor system, descend through the birth canal or suck to feed, among other functions (BRMT, 2016).
However, some of them will disappear following a pre-established order during the first year of life (García-Alix and Quero, 2012).
The reflexes are part of the posterior motor development of the newborn and, therefore, its evaluation is part of the neonatal neurological examination. This allows us to assess the general development of the nervous system (García-Alix and Quero, 2012).
When there is some type of deficit at the neurological level, it is possible that some of the primitive reflexes remain active during late stages of development, and will hinder the acquisition of motor skills as well as sensory perception and cognitive development (BRMT, 2016).
When do reflections appear?
Already during the prenatal stage evidence of primitive reflex activity can be observed (Carlson, 2000; Roselli and Matute, 2010).
Specifically, around the sixth week of gestation, when touching the skin surrounding the mouth, a contralateral flexion of the neck can occur (Roselli and Matute, 2010).
Between the sixth and eighth week of gestation , reflex responses can be observed by stimulating the skin of the upper area of the chest, the palms of the hands or face (Roselli and Matute, 2010).
In the case of the twelfth week of gestation , approximately the whole corporal surface is sensible, with the exception of the back or the crown. Consequently, reflex responses become more specific (Roselli and Matute, 2010).
Types of reflexes in the newborn or neonate
The primitive reflexes can be divided into two large groups: primitive postural reflexes and tactile primitive reflexes (García-Alix and Quero, 2012):
- Primitive postural reflexes : they occur as a consequence of the stimulation of the receptors of the vestibular apparatus by the movement of the head-reflex moro-. At the neurobiological level, they are mediated at the level of the brainstem.
- Primitive tactile reflexes : they occur as a result of tactile stimulation, plantar response, Galant reflex, grasping reflex, etc.). At the neurobiological level, they are mediated at the level of the spinal cord.
Postural reflexes (García-Alix and Quero, 2012)
The most relevant postural reflexes are: Moro reflex, asymmetric tonic cervical reflex and the labyrinthine tonic reflex. Everything except Moro’s reflection, are characterized by developing with variable and incomplete responses.
This type of postural reflexes is only observed during postnatal life, because there is a suppression during the gestation period so that the fetus does not respond to every movement that the mother makes.
– Reflection of Moro
The moro reflex or startle reflex occurs when the baby is startled by an intense sound or movement. In response, the baby moves its head backwards, spreads its arms and legs (University of Rochester Medical Center, 2016).
The Moro reflex can be triggered as a consequence of several stimuli: sudden sound or a sudden movement of the surface where the baby is placed, among some others (García-Alix and Quero, 2012)
When any of the previous stimuli appear, in the baby there is a complete opening of the hands, followed by a flexion of the fingers (forming a “C” between the thumb and the index finger) (García-Alix and Quero, 2012)
The Moor reflex has several phases (García-Alix and Quero, 2012):
- First phase : extension of the forearms.
- Second phase : adduction of the arms and flexion of the forearms.
- Final phase : crying or grimace of anxiety.
– Reflex cervical tonic asymmetric
The asymmetric tonic cervical reflex occurs when the baby is relaxed and lying down and moves the head to the side. The arm on the side where the head is positioned extends away from the body with the open hand and the one on the opposite side is flexed (National Institutes of Health, 2013).
If the baby turns his head to the contralateral side, the pattern of movements is reversed (National Institutes of Health, 2013).
– Labyrinthic tonic reflex
When the baby is in the supine position (the baby is lying on the back face up with the extremities extended), the extension of the head produces a retraction of the shoulders and extension of the legs (García-Alix and Quero, 2012).
In prone position (the baby is lying face down with the head on its side), the flexion of the head produces a flexion of the legs (García-Alix and Quero, 2012).
Tactile reflexes (García-Alix and Quero, 2012)
Tactile or cutaneous reflexes occur as a result of stimulation of the skin in a specific area. This stimulation triggers a motor response that takes place in the same place where the stimulation was applied.
The most important tactile reflexes are: suction reflex, search reflection or snout, Galant reflex or trunk invurvation, Vollmer reflex and Perez reflex, cross extension reflex, magnet reflex or magnetic reflex, step reflex, automatic gait reflex, positive support reflex (pallar pressure, finger extensor, babinski reflex , plantar response).
– Suction reflex
When a tactile stimulation of the baby’s upper palate or tongue is performed, it begins to suckle (University of Rochester Medical Center, 2016).
The suction reflex has a main function in survival, since it is essential for the feeding of the newborn (García-Alix and Quero, 2012).
– Reflection of search or snout
When the corner of the mouth or cheek is stimulated on the surface of the face on one side and then on the other, the child responds by moving the lips and tongue towards the location of the tactile stimulus (García-Alix and Quero, 2012).
– Reflection of Galant
Galant reflex or trunk curvature occurs when the skin along the baby’s spine is stimulated while the baby is lying face down (National Institutes of Health, 2013).
Specifically, this reflex can be produced by rubbing the skin that is on both sides of the spine with the index finger, from the shoulder to the buttocks. tactile (García-Alix and Quero, 2012).
Automatically, after the stimulation the baby performs a curvature of the spine to the side in which the stimulation is taking place (García-Alix and Quero, 2012).
– Reflection of Vollmer and reflection of Pérez
In the Vollmer reflex, when a firm pressure is applied along the spine, there is a flexion of the arms and legs with a dorsal extension of the spine and neck (García-Alix and Quero, 2012).
In Pérez’s reflex, when a firm pressure is applied along the cervico-thoracic spine, there is a flexion of the arms and legs with a dorsal extension of the lower spine (García-Alix and Quero, 2012).
– Cross extension reflex
In the crossed extension reflex, when a tactile stimulation is applied to the sole of the foot while the extremity in which it is being applied is extended, it results in a response composed of three phases (García-Alix and Quero, 2012) .:
- First phase : spontaneous flexion of the leg that is free.
- Second phase : extension or opening of the toes in which the stimulation was performed.
- Third phase : extension and adduction of the free foot to the stimulated.
– Magnet reflection or magnetic reflection
When the baby is lying on his back and light pressure is applied with the thumb on the floor of both feet, the baby extends his legs to maintain contact (García-Alix and Quero, 2012).
– Step reflection
The step or placement reflex occurs when the baby is in a vertical position held below the armpits (García-Alix and Quero, 2012).
When a stimulation is applied under the back of the foot, the baby responds by elevating the foot and placing it on the surface, through a flexion of the knee and hip with an extension of the foot García-Alix and Quero, 2012).
– Automatic gear reflex
The automatic gait reflex occurs when the baby is placed in a vertical position, placing his feet on a surface (García-Alix and Quero, 2012).
The baby, facing this position, responds by straightening the lower extremities and the trunk, and making a succession of steps, synchronizing hip flexion with that of the knees (García-Alix and Quero, 2012).
– Palmar pressure reflex, extensor digitorum, babinski reflex, plantar response
The skin surface of the palm of the hand and the sole of the foot, with one of the skin areas of the body more sensitive to stimulation, so there are several primitive reflexes associated with these:
- Palmar pressure reflex : when we put a finger on the palm of a newborn’s hand, it reacts by closing it around the finger. If you try to withdraw, the newborn squeezes his fingers, exerting force against tactile stimulation (National Institutes of Health, 2013).
- Extensive reflex of the fingers or digital response : an opening of the fingers of the hand occurs when the surface of the little finger or the back of the hand is repeatedly stimulated (García-Alix and Quero, 2012).
- Reflection of Babinski : when the surface of the sole of the foot is caressed, the fingers are fanned out (National Institutes of Health, 2013).
- Plant response : when an intense tactile stimulation is applied on the lateral area of the foot plant, from the heel to the thumb, an extensor response occurs on the thumb (García-Alix and Quero, 2012).
What is the temporal evolution of primitive reflexes?
- Moro reflex : it appears well established around the 37th week of gestation and disappears approximately between 5-6 months of age.
- Asymmetric tonic cervical reflex : it appears well established around 1-2 months of age and disappears approximately between 6 and 9 months of age.
- Suction reflex : it is well established between week 34 and 36 of pregnancy and disappears about 4 months of age.
- Reflection of search : it is well established between week 34 and 36 of gestation and disappears about 4 months of age.
- Palmar pressure reflex : it is well established on week 32 of gestation and disappears between 6 and 9 months of age.
- Reflection of Galant : is present and well established on week 32 of gestation and disappears between the first and second year of life.
- Labyrinthine tonic reflex : it is present approximately between 2 and 4 months of age and disappears between 11 and 24 months after the postnatal stage.
- Reflection of localization : it is present and well established on week 40 of gestation and disappears between the first and second month of life.
- Reflex of march : it is present and well established on week 40 of gestation and disappears between the first and second month of life.
- Reflection of extension : it is present and well established on week 40 of gestation and disappears between the first and third month of life.
Why are reflexes evaluated in newborns?
As we have pointed out in other sections, there are several reasons to perform an analysis of primitive reflexes in newborns (García-Alix and Quero, 2012):
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- They help us assess the general development of the baby’s nervous system.
- They allow us to evaluate the specific integrity of the central nervous system (CNS).
- In some cases, they may have localization value and, therefore, help us identify the possible location of an injury or structural damage.