Specific statistics on the incidence of hypotonia are unavailable, but the reader should be aware that hypotonia is a common newborn presentation. The epidemiologic literature has not described the relationship between the incidence of hypotonia and maternal behaviors. The reader is referred to the general epidemiologic information presented in Chapter 16 (The Premature and Low–Birth-Weight Infant).

The following are indications of hypotonia:

When an infant is first noted to have diffuse hypotonia after discharge from the nursery, there are several diagnostic possibilities. Priorities are the infant’s medical status, requirements, and maturational state.

The infant with hypotonia who develops increased muscle tone after nursery discharge requires a diagnostic evaluation if earlier studies to provide a reasonable etiology were not done. For the infant whose cranial scans in the nursery showed lesions of cerebral insults (such as periventricular leukomalacia, porencephaly, and enlarged ventricles), hypotonia may be evident at first, even if spasticity emerges later.

After 9 months of age, manifestation of significant delays becomes increasingly unlikely if the infant has progressed normally through developmental stages. For example, infants who sit and crawl normally will be able to ambulate. By this age, the provider already should have identified any infant who is exhibiting gross motor delays or limitations, referring the child to an appropriate intervention program. The infant who exhibits deviations in normal motor function is likely to have alterations in pulling to stand and walking, unless interventions have minimized these problems. Some variations still may occur dynamically with pulling to stand or ambulating, even though previous patterns were normal. The reader who desires a review of normal motor development is referred to Chapter 8.

If a pattern of development is deviated enough, intervention may need to begin before a delay actually appears. The provider must inform the family about which functional patterns may be inhibited, while giving them specific instructions for activities that will promote the infant’s development. With very mild deviations and borderline or no delays, this plan may be adequate in guiding the baby toward subsequent normal gross motor development. With early intervention, infants with mild delays and dynamic deviations may progress to normal functional levels and no longer be physically challenged. Depending on how a community manages their early intervention services, a provider may be able to follow the child and coordinate service delivery with the support of therapists until the child achieves functional mobility.

Several rehabilitative devices can assist the child with hypotonia to improve limb mobility and usefulness. In addition to standard devices, therapists can individualize rehabilitative equipment and regimens when specific needs exist. The provider should expect that therapists will recommend at least some of the following aids and activities for the child with hypotonia:

To assess the infant appropriately, the provider needs adequate time to obtain a thorough history and to perform a complete examination of function and tone. The history should include the infant’s feeding patterns, temperament, activity level, sociability, tolerance of handling, and any parental concerns.

The examination requires placing the infant in the following positions: supine, prone, side-lying, and supported sitting on the examining table and parent’s lap. The provider also should hold the child suspended in the air prone and sideways. The provider observes and handles the infant to assess quality of movements, tonal responses, primitive reflexes, quality of grasping, visual attending to hands and toys, social regard, and the ease with which crying can be calmed.

The earliest signs of hypertonia are reflected in the head, trunk, and extremities, with patterns often seen as precocious development. The following features identify hypertonia:

The foregoing manifestations of hypertonia are key to detecting significant motor problems. They also are the focus of intervention programming, with therapies directed at inhibiting these signs to facilitate more volitional control. Hypertonic patterns and reflexes can predict pending delays even when actual milestones are still normal. Not all these signs and reflexes will be present, and they may appear at different times. While continuing to support the family, the provider should refer the infant with hypertonia to a pediatric neurologist for a more focused evaluation and to devise appropriate management strategies.

Feeding difficulties that may occur in the infant with hypotonia or hypertonia can be dealt with by improving positioning. A specially trained speech therapist can work with the baby to enhance oromotor responses.

Causes of CP vary; it may be congenital or result from an insult prenatally, at birth, or during early infancy. Manifestations of CP may be delayed.

In premature infants, the less-developed vascular beds are particularly prone to hemorrhage in the germinal matrix, with involvement in the intraventricular or periventricular areas. The latter problem leads to periventricular leukomalacia, one of the most frequently seen predisposing cerebral insults among premature infants who develop CP. Many factors can establish an environment for cerebral injury, however, and prenatal factors are increasingly being considered more relevant. Infections are emerging as an important cause. Most premature infants do not go on to have CP.

Nearly half the children who have CP were not premature (Nelson, 1998). Causes of CP in term infants vary. The cerebrum is more mature and less vulnerable in term infants than in premature infants, especially because its vascularity is improved. The mechanics of the delivery process and all the etiologies that can lead to malformation or brain injury prenatally, during birth, or in the neonatal period, however, still can occur. For many children, a cause is never identified. The reader should refer to a current pediatric neurology text for further information on the causes of CP.

Infants with CP present with different categories of muscle tone and movement disorders. A spastic muscle tone pattern is most common, occurring in approximately 75% of cases (Nelson, 1998). Spasticity is a specific form of hypertonicity, resulting from injury to the pyramidal part of the nervous system. Spasticity manifests as abnormal upper motor neuron reflexes, persistent primitive reflexes, increased muscle tone, and increased resistance to muscle stretch or elongation. The latter condition is known as a clasp knife phenomenon, with distinct release of resistance during stretching that is reproducible. Spasticity usually occurs in a diplegic, hemiparetic, or quadriparetic pattern, reflecting the location of cerebral motor involvement. Diplegia affects primarily the lower extremities. Hemiparesis affects the upper and lower extremity on the same side. Quadriparesis affects the bilateral upper and lower extremities. The hemiparetic form is slightly less frequent than the other variants, while the diplegic pattern is particularly likely with prematurity. Triplegic presentations are rare, usually with relative sparing of an upper extremity.

The provider should initiate intervention with physical, occupational, and speech therapies as soon as functionally limiting signs appear. Therapists should instruct family members about their role in carry over of therapy. Rehabilitative activities require comanagement by therapist and family so that interventions occur daily or more frequently. The provider’s role as coordinator of services is key to successful intervention, because he or she can support the family through the stresses and demands of carrying out a therapeutic regimen several times every day.

The therapy team teaches the family how to carry out proper stretching methods at home, where the child is most comfortable and relaxed. The family can establish a routine that works best and allows adequate time for the activity. Diversion of the stretching regimen to home means that therapists can use their sessions to concentrate on helping the child develop more varied mobility and postural control skills.

Family and therapists must incorporate supportive seating early for proper postural symmetry and trunk alignment that will prevent spastic trunk hyperextension or underlying hypotonic sagging. They must facilitate rolling, crawling, sitting, and eventually, assisted standing. These children usually require AFOs to control toeing and to maintain proper alignment with standing. They may need AFOs very soon if sustained plantar flexion posturing is of a degree that would lead to range loss. Children progress to gait training when they have achieved adequate postural control. Children who are able to override their primitive reflexes by 18 months and sit independently with control by 2 years are likely eventually to walk at a functional level, although usually with braces (Nelson, 1998).