Evolutionary neurology studies the development of the nervous system in the first years of life. The neurologist, neonatologist or pediatrician that carries out the neurological exam, compares the results with the pattern of normal evolution outlined by trimesters of the baby's age.
When carrying out this check up it is necessary to keep in mind the moment in when the childbirth took place and the hours or days that have lapsed from that moment.
In the newly born at least 70 neurological signs can be explored, this progressive exam will increase with the data contributed by the follow up exams. This exploration, besides other aspects such as the motor and sensory development, basically assesses:
the active and passive muscle tone.
the reflexes and/or postural reactions.
The tone
The active muscle tone is the one that refers to the development of the motor acquisitions: control of the head, to remain sited, to walk independently, etc.
Placing the new born standing up, held from under the armpits or allowing him to lean on slightly on feet soles, if he straightens out with vigor on the legs lifting the neck and the head, he demonstrates that he maintains a good, active muscular tone. This is also proven when sitting down from laying down, the baby maintains the head up for some seconds.
The passive muscular tone is examined based on the extensibility of the corporal segments and, in a supplementary way, in the flexion of the members, some with regard to the others (angle of abductors, heel-ear, posture of thighs in hyperextension, popliteus angle, angle of dorsal flexion of the foot, maneuver of the scarf, etc.).
The fluctuations in the muscular tone are very marked during the first year of life. In the first trimester the level of tonicity is very high. The baby remains with the arms and legs flexed, the hands closed with the thumb outside of the fist and the head rotated towards one side.
During the second trimester this attitude in tension diminishes and is substituted by another in which the baby appears much more flexible and calm in his movements. The hands frequently open up, the head remains long periods in the half line and it is easy for him to extend his arms and legs.
During the third and fourth trimester these characteristics are even more evident because the muscular flexibility increases to such an extent that the boy or girl is able to take the feet to the mouth with easiness.
Between the 12 and 16 months, the flexibility is stabilized, providing the appropriate tone for the motor acquisitions of this period and of the coming stages.
The muscular tone varies in diverse circumstances, for example when the baby sleeps, the tone diminishes to the maximum, however when he is exalted and cries or when he feels intense emotions there will be variations.
The observation of the baby's muscular tone is very important, not only for its diagnostic contribution, but because starting from these observations we can do some exercises to get patterns of passivity or extensibility next to normality, it can also contribute data with regard to possible deviations that, with neurological treatment and stimulation could correct abnormalities.
The reflexes.
When the baby is born, he has automatic answers for certain stimuli that favor the adaptation to his new setting. We call these answers reflexes. We can distinguish the primary or archaic reflexes and the secondary or postural responses.
The primary or archaic reflections are present during the first months of life. The date in which they disappear can be variable, although their persistence after five months should be a reason for a deeper exploration by the neurologist. These are some of the primary reflexes that are usually checked:
Suction reflex . When placing any object touching the lips, the baby sucks repeatedly.
Swallowing reflex . It completes the previous one and it allows the boy's correct feeding.
The rooting reflex . It is related with the two previous reflexes and it persists until the second month of life. When touching the cheek, the newborn turns his mouth toward the touched side. In the same way, he flexes his head when we touch him on the chin or the forehead.
Step reflex . With the baby in vertical position, held by the armpits, with the feet in contact with a hard surface, when he is slightly leaned forward, the baby advances the feet alternating, as if he was walking.
Some researchers maintain that the walking unchained by this reflex has a very sophisticated grade of adaptation, since if while walking the baby finds a small obstacle, he adapts his step and avoids it. He is also able to take some steps on an upward slope.
This reflex usually disappears between two or three months of age.
Grasp reflex . When placing any small object in the hand, a strong grasping reaction is provoked in the fingers. This reflex usually disappears between two and four months.
Answer reflex to traction . When one obtains the grasping of the fingers of both hands, as we have described, on the index fingers of the adult, or on a bar of similar thickness, the baby is capable of staying suspended with all or part of his weight.
In the second trimester, this grasping reflex is replaced by voluntary grasping so that when the adult places his fingers, the baby will take them as a support to try to sit down.
Tonic neck or fencing reflex . With the baby tossed on his back, he rotates the head towards one side and maintains his arms in the posture of a “swordsman”, that is, the arm of the side towards which he rotates his head is extended and the other is flexed at the height of the shoulder. The legs are usually crossed.
Moro reflex . It consists of a flexion of the trunk, shoulders, hips, hands and feet, at the same time that he extends his elbows, knees and fingers; everything followed by a cry. This reaction is obtained when faking a fall back of the baby.
During the first trimester, the reflex is complete and during the second trimester, the response is limited to opening his hands and crying. It later disappears.
Toe curl reflex . When a fine object, for example a pencil, touches the back side of big toe, it provokes that the toes flex, even ending up retaining the object.
This reflex disappears at a later point, approximately at about the ninth months.
Eye reflexes , mainly:
Eyelid reflex. The baby closes his eyelids if there is a sudden strong light or loud noise nearby.
Dolls eyes . It is present during the first month. When the baby moves his head towards one side, the eyes appear to move to the opposite side. The reflex disappears when the baby establishes his visual fixation.
Secondary reflexes or postural responses. They appear after the primary reflexes. They are important in the follow up of the baby's neurological evolution and they are included as automatic in the behavior of the human being throughout his life. Among them we have:
Lateral or backward propulsion. When the baby is sitting down without any help and he is pushed on one of his sides, at the height of the shoulder, he extends his arm on the opposite side to prevent the fall.
The same way, when the baby is pushed backwards, he uses his hands to try to keep his balance.
Parachute reflex . When the baby is suspended on his belly and he is suddenly leaned forward, he makes a motion to protect himself from the fall, extending his arms and spreading his hands.
This reflex appears between six and nine months and, as some of the others, its absence can be a sign of a neurological injury. This is why it is important to verify it.
SELF CHECK QUIZ |
SECTION 2 - BLOCK 2 |
CHAPTER 4 |
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1. The active muscular tone is observed by checking the extensibility of the body segments and the flexion of the members with regards to each other.
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2. The reflexes are automatic responses to specific stimuli.
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3. The primary or archaic reflexes are present from birth and disappear within the first four months of life.
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4. The eyelid closure and the doll's eye are eye reflexes.
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5. The most important secondary reflexes are suckling, automatic step and hand grasping.
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