tone & posture in children

tone is functionally as resistance to passive movement. it is separated into postural tone and phasic tone. phasic tone is the result of rapid stretching of a tendon and the muscle spindle, however postural tone is the result of a steady, restrained strech on muscles. hypottonia is a decreased resistance to passive movement. the term floppy is frequently used to describe hypotonic children. in childhood central nervous system dysfunction, may cause increased or decreased muscle tone. on the other hand muscle spindles and golgi tendon organs are encapsulated structures found in skeletal muscle. the main skeletal muscle fibers or extrafusal fibers are innervated by large diameter alpha motor axons. neurological examination of the infants involves examination of the resting posture passive and active tone. posture is appreciated by inspecting the undressed infant lies undisturbed. • the head is preferentially turned to the right for longer periods than to the left • term infants have predominant flexor tone with resultant flexion of the arms at the elbows and of the legs at the knees • limb position and posturing should be symmetric • while supine, the infant manifests spontaneous limb movements that are often symmetric during the first few months of life, normal hypertonia of the flexors of the elbow, hips and knees occurs. the hypertonia decrease markedly during the third month of life, first in the upper extremities and later in the lower extremities, at the same time, tone in neck and trunk increases. between 8 and 12 months of age, a further decrease occurs in the flexor tone of the extremities together with increased extensor tone. the scarf sign is used for examination of hypotonia in upper extremity and the fall-away test is used for examination of hypotonia in lower extremity. in fall away response. the infant is suspended by the feet, upside down, and each lower extremity is released in turn. the rapidity with which the lower extremity drops when released is noted. normally, the extremity maintains its position for a few moments, then drops. in hypotonia, the drop occurs immediately but, in hypertonia, the released lower extremity remains up. gentle manipulation of infants limb allows for assessments of muscle tone & strength. the infant should be held in horizontal suspension, the hypotonic weak infant appears to be looped over the examiner’s arms when held in vertical suspension the hypotonic weak infant tend to slide through the examiner’s hand. infants with increased tone manifest an opisthotonic position and infants with increased tone in vertical suspension manifest scissoring (crossing of the legs because of excessive involuntary adductor magnus contraction). infants with increased tone manifest obligate extension in both vertical & horizontal suspension.