Development of Postural Equilibrium

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Development of Postural Equilibrium & Oculomotor Control : 

Development of Postural Equilibrium & Oculomotor Control Maha H Abou-Elew Associate Professor of Audiology Cairo University

Postural Development : 

Postural Development Control of balance: Vision Proprioceptive vestibular systems motor system

Development of the vestibular system : 

Development of the vestibular system Anatomical Physiological Integration within the CNS

Neurologic developmental anatomy : 

Neurologic developmental anatomy Brain Growth Neuronal Growth and Organization Myelination and Development Cerebral Hemisphere Myelination

Neuronal Growth and Organization : 

Neuronal Growth and Organization By 36 weeks gestation, the process of neuronal proliferation is nearly complete. Growth of the individual neurons plus the proliferation of dendritic and axonal processes and connections is responsible for most of the brain’s growth. During the organization process of brain development there is increasing dendritic arborization, synaptogenesis, and axonal connections, which make a significant contribution to brain growth as well as the maturation and development of brain function.

Myelination and Development : 

Myelination and Development Myelination begins early in the 3rd trimester with the most rapid period of myelination occurring in the first two years of life. The corticospinal tract starts to myelinate at 36 weeks gestation and myelination is completed by the end of the 2nd year of life. Myelination of the corticospinal tract begins at the proximal portion of the axon and the shortest axons are the first to myelinate (head-to-toe myelination pattern)

Key Principles : 

Key Principles First, the development of motor control proceeds in a head to toe fashion. The baby first develops head control (head support), then trunk control (sitting and pelvis stabilization), and finally dynamic control of the all body (standing and walking). Second, primitive reflexes (such as the Moro, grasp, and Galant, stepping) are normally present in the term infant and diminish over the next 4 to 6 months of life. The postural reflexes (such as the positive support reflex, Landau, lateral propping and parachute) emerge at 3 to 8 months of age.

Slide 8: 

Mastering balance is a difficult task Head holding: 2-3 months Sitting: 5-6 months Standing: 10-12 months Walking 4 legs : variable, 8 to 9 months Independant Walking: 12 months ± 5 (maximum 18 months) 10 to 12 years to reach highest balance performances

Head, trunk and lower extremities control (head support, sitting, standing and walking) : 

Head, trunk and lower extremities control (head support, sitting, standing and walking) Sitting Walking with Support (Cruising) Walking (Toddler’s Gait) Head support 2- 3 months 6 months 12-14 months 10-12 months

Motor control : 

Motor control Head Control / Head support The strength and tone of the neck extensors can be tested by having the baby in sitting position and neck flexed so the baby’s chin is on the chest. The baby should be able to bring the head to the upright position. The neck flexors can be tested by having the head in extension while in the sitting position. The baby should be able to bring the head to the upright position. These tests are an extension of the test for head lag and are done at the same time.

Motor control : 

Motor control SittingIndependent sitting is accomplished by 5- 6 up to 8 months. This baby has good sitting posture (head erect and spine straight) and has enough stability to reach for objects with both hands. He even stretches to obtain an object without loosing his balance.

Motor control : 

Motor control Stand, Walks with Support The infant can stand, pull to a stand and cruise. Cruising is walking along a piece of furniture while holding on. It usually develops between 10 to 12 months. Along with cruising, the infant can take steps while holding on but he’s not ready to walk unsupported.

Motor control : 

Motor control Toddler’s Gait Independent walking is achieved between 11 and 15 months of age. This 12 month old infant has a typical gait of an infant that has just learned to walk. He has a wide base, is unsteady, and toddles. His arms are held at near shoulder level in a high guard position. This is a protective position and probably aids in his balance. As he matures, his arms will come down to a low guard position, then into the usual associated arm movements seen with mature walking. An infant is delayed if they aren’t walking by 16 months.

Primitive reflexes : 

Primitive reflexes Suck, Root reflexnewborn 4-5 ms Moro’s reflex newborn 3 ms 6 ms

Primitive reflexes : 

Primitive reflexes Galant reflexNewborn 4 months Grasp reflex Newborn 4-6 months

Primitive reflexes : 

Primitive reflexes Stepping reflex Newborn Planter reflex “Babinski sign” Newborn

Primitive reflexes : 

Primitive reflexes Suck, Root reflexThe baby should have a strong coordinated suck reflex with good stripping action of the tongue. There should be resistance to pulling out the pacifier. A root reflex is obtained by gently stroking the cheek towards the lips. The baby should open the mouth towards the stimulus and turn the head to latch on to the object.

Primitive reflexes : 

Primitive reflexes The Moro reflex It is obtained by holding the baby’s head and shoulders off of the mat with the arms held in flexion on the chest. The examiner suddenly lets the head and shoulders drop back a few inches while releasing the arms. The arms should fully abduct and extend, then return towards the midline with the hand open and the thumb and the index finger forming a “C” shape. An absent or incomplete Moro is seen in upper motor neuron lesions. An asymmetric Moro is most often seen with a brachial plexus lesion. The brachial plexus palsy is on the side of the poorly abducted arm.

Primitive reflexes : 

Primitive reflexes The Galant reflex (trunk incurvation) It is obtained by placing the baby in ventral suspension, then stroking the skin on one side of the back. The baby’s trunk and hips should swing towards the side of the stimulus.

Primitive reflexes : 

Primitive reflexes The grasp reflex Placement of the examiner’s finger in the palm of the hand or on the sole of the foot will cause flexion and grasping of the fingers or toes. One should avoid touching the dorsum of the hand while eliciting the grasp reflex because stimulating the back of the hand causes a hand opening reflex to occur. With the two competing reflexes, the grasp response will be incomplete or inconsistent. You can actually see this happen with the baby that is being examined. The grasp reflex can be reinforced by applying traction on the arm. Newborn baby

Primitive reflexes : 

Primitive reflexes Stepping reflex The stepping or walking reflex is obtained by holding the baby upright over the mat with the sole of the foot touching the mat. This initiates a reciprocal flexion and extension of the legs and it looks like the baby is walking. Newborn baby

Reflexes : 

Reflexes Plantar Reflex The normal response to stroking the lateral aspect of the plantar surface of the foot is extension of the great toe and fanning of the other toes. If the stimulus is brought across the ball of the foot then a grasp reflex will be elicited and the toes will plantar flex. The up going toes or “Babinski sign” is normal in the infant and may be present for the first year of life because of the incomplete myelination of the corticospinal tracts. There is still a lot of plantar grasp at 6 months age as well as withdrawal, which makes testing for the plantar response difficult at this age. The toes are still up going until one year of age. The most useful finding at this age is if there is asymmetry in the toe findings

Postural Reflexes : 

Postural Reflexes The development of postural reflexes is essential for independent sitting and walking. They include: - Positive Support Reflex - Landau reflex - Lateral Propping - Parachute reflex

Postural Reflexes : 

Postural Reflexes Positive Support Reflex It is the first postural reflex to develop and is present by 3 to 4 months of age. When the baby is placed in vertical suspension with the feet touching the mat, the baby will extend the legs and attempts to support his weight while being balanced by the examiner. By 5 to 6 months of age the baby fully supports his weight while standing and by 7 months enjoys bouncing. It is necessary for erect posture and blends into volitional standing. Infants with prenatal or perinatal corticospinal tract disease will often refuse to support their weight on their feet.

Postural Reflexes : 

Postural Reflexes Landau reflex The Landau is an important postural reflex and should develop by 4 to 5 months of age. When the infant is suspended by the examiner’s hand in the prone position, the head will extend above the plane of the trunk. The trunk is straight and the legs are extended so the baby is opposing gravity. When the examiner pushes the head into flexion, the legs drop into flexion. When the head is released, the head and legs will return to the extended position.

Postural Reflexes : 

Postural Reflexes Lateral Propping (or protective extension) It is essential for the baby to be able to sit independently. This postural reflex develops at 5 to 7 months of age. Anterior propping actually develops first, then lateral propping. For anterior propping the baby will extend the arms forward to catch himself and prevent falling forward. Lateral propping occurs when the baby is falling to one side or the other and he extends the arm laterally to catch himself. Asymmetric lateral propping can be an early sign of hemiparesis. The baby will prop on one side but on the paretic side he will not extend the arm to catch himself.

Postural Reflexes : 

Postural Reflexes Parachute reflex It is the last of the postural reflexes to develop. It usually appears at 8 to 9 months of age. When the baby is turned face down towards the mat, the arms will extend as if the baby is trying to catch himself. Prior to developing this reflex, the baby will actually bring the arms back to the plane of the body and away from the mat. Note that the absence of parachute can be due to an absence of semicircular canals without any other neurological disorder. No canal= no head rotation percived fast enough to anticipate= no protection by the arms

Vestibular system and postural and motor control : 

Vestibular system and postural and motor control Vestibular system has: Two main parts Two Functions Otolith---------- axial tonic control (head support, sitting, standing and walking) SCC------------ fine control during head movement (head rotation)

Maturation of the vestibular system : 

Maturation of the vestibular system The vestibular receptors are mature at birth (not like vision and proprioception where the receptors characteristics follow growth) Integration of the vestibular information is a progressive process that take place during the first decade of life Posturomotor milestones are important indicators of the central nervous system vestibular integration.

OCULOMOTOR CONTROL : 

OCULOMOTOR CONTROL The baby is able to visually track an object throughout the horizontal and vertical planes (pursuit). An interesting or colorful object is most helpful. To test visual fields, have the baby focus on an object in front of him and then bring a second object from behind him until he sees the object in his peripheral vision. He should turn toward the new object (vestibulo ocular and OPK). Saccadic eye movements are tested by using interesting toys and sounds and watching the eyes jump from object to object. At 6 months

Motor control : 

Motor control Head Control / Head support The strength and tone of the neck extensors can be tested by having the baby in sitting position and neck flexed so the baby’s chin is on the chest. The baby should be able to bring the head to the upright position. The neck flexors can be tested by having the head in extension while in the sitting position. The baby should be able to bring the head to the upright position. These tests are an extension of the test for head lag and are done at the same time.

Slide 32: 

Mastering balance is a difficult task Head holding: 2-3 months Sitting: 5-6 months Standing: 10-12 months Walking 4 legs : variable, 8 to 9 months Independant Walking: 12 months ± 5 (maximum 18 months) 10 to 12 years to reach highest balance performances

Slide 33: 

Parameters of walking are changing after the first independent steps (A, ledebt, B, Bril, SR Wiener-Vacher 1993-95)

Slide 34: 

Lateral movement antero-posterior movement 10 cm 10 cm 13 months of experience of independent walking = 2 years old 6 months after the first independent steps Gravity center displacements is function of walking experience (A Ledebt, B. Bril 1994)

Slide 35: 

Head stabilization during walking (A Ledebt 1994)

Slide 36: 

0 % coordination (A Ledebt 1994) 2 months and half of independent walking experience 80 70 60 50 40 30 20 10 0 0 20 40 60 80 100 weeks of walking experience Index of coordination of the head movements during walking Coordination in %

Vestibular information play an important role in : 

Vestibular information play an important role in Stabilizing the vision: vestibulo ocular pathways Stabilizing the posture: vestibulo spinal pathways Posturomotor development in children: absence of vestibular information early in life induces axial hypotonia and delays in independent walking but also secondary cognitive and psychomotor dysfunction (representation in space self and environment, reading writing…called « associated disorders »).

Slide 38: 

ROLE OF VESTIBULAR INFORMATION vestibulo-spinal pathways axial control plomb line vestibulo-oculaires pathways head-eye rotation control Oculomotor & posturomotor control & Cognition

Slide 39: 

Vestibular functional evaluation is now available in children: canal (low, middle and high frequencies) and otolith function

Slide 40: 

Vestibular responses are different from adults and vary in function of age CALORIC TEST (30°, 44°) <0.01 Hz OVAR (vor) Off vertical axis rotation 60°/s, 13° tilt VEMP (v-spinal) Vestibular evoked myogenic potentials EVAR Earth vertical axis rotation 40°/s² (0..1Hz) Which tests are possible in children? ALL Head impulsion test (Halmagyi) HIT (0.5Hz)

Slide 41: 

Canal VOR during pendular stimulation : 8 months old child // adult

Slide 42: 

The changes of the otolith VOR follow the steps of maturation of the posturo-motor control and particularly independent walking OtolithVOR during OVAR

Slide 43: 

Otolith VOR changes relative to the acquisition of independent walking: Horizontal modulation increases Vertical modulation decreases Biais does not vary

Slide 44: 

Time relative to onset of walking (weeks) 100 80 60 40 20 0 -20 -40 0 20 40 60 80 100 80 60 40 20 0 -20 -40 0 20 40 60 80 100 80 60 40 20 0 -20 -40 0 20 40 60 80 OVAR vertical modulation OVAR horizontal modulation Changes in responses to OVAR are correlated to the period of acquisition of independent walking OVAR vertical modulation OVAR horizontal modulation

Slide 45: 

OTOLITH FUNCTION (Averaged modulation amplitude, of the VOR to OVAR, °/s ) INDEPENDENT WALKING ACQUISITION IS DELAYED WHEN VESTIBULAR FUNCTION IS ABSENT AT BIRTH (13 patients with no caloric canal responses at 20°C) CANAL FUNCTION (Averaged responses to EVAR : Maximal slow phases velocity ,°/s)

Slide 46: 

Vesicle with or without a sensory epithelium (saccule?) Absence of canal function // otolithique

Slide 47: 

OTOLITH FUNCTION IN ABSENCE OF CANAL FUNCTION CHARGE Association: no canals at the CT scan No CHARGE but absence of canals at the CT Scan Canals at the CT Scan but not functional OTOLITH INFORMATION IS REQUIRED FOR AXIAL TONIC CONTROL

Slide 48: 

Sensation of verticality in children SUBJECTIVE VERTICAL AND HORIZONTAL MEASUREMENTS Before 4 years: the concept of vertical is not understood, however the body can reproduce verticality From 4 to 8 years: verticality can be reproduced but with high variability: +/- 4 degrees After 8 years: the test is performed as precisely as adults: +/- 2 degrees

Slide 49: 

MATURATION OF THE VESTIBULAR RESPONSES The maturation of the vestibular system is not complete at birth. Vestibulo-spinal responses are already integrated at birth (VEMP): basic primitive control. Vestibulo-ocular responses (otolith and canal) are progressively integrated: fine control following the ongoing visual system maturation during the first decade of life. Vestibulo-cortical responses are influenced by many factors to complete their integration (continuing over lifetime?).

Slide 50: 

ROLE OF VESTIBULAR INFORMATION vestibulo-spinal pathways axial control plomb line vestibulo-ocular pathways head-eye rotation control Oculomotor & posturomotor control & Cognition

Slide 51: 

Consequences of complete absence of vestibular information (20% of the profoundly deaf children) No stabilisation of the trunk and head: energy and attention consumption (Anderson et al) and difficulties to lear how to write No reference to verticality, desorientation in space (Brandt et al) and body representation No gaze stabilisation during movement : decrease of dynamic visual acuity (Rine et al) difficulties to learn to read and write Difficulties to overcome other visual or sensory acquired impairments

Slide 52: 

Thank You

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