Motor Impairment

Cerebral Palsy

Cerebral Palsy (CP) is a general term to describe a group of chronic conditions that impair control of movement and posture. CP is due to malformation of or damage to motor areas in the brain which disrupt the brain's ability to control movement and posture. Symptoms of CP may range from mild to severe, change over time and differ from person to person, and include difficulty with balance, walking, and fine motor tasks (such as writing or using scissors) and involuntary movements. Many people with CP also have associated cognitive, sensory, social, and emotional disabilities (NIDS, 2005).

The diagnosis of CP may not become certain until the second year of life. As many as 17 to 48 percent of preterm infants demonstrate neuromotor abnormalities during infancy (e.g., abnormal muscle tone or asymmetries) (Allen and Capute, 1989; Khadilkar et al., 1993; Pallas Alonso et al., 2000; Vohr et al., 2005). Some of these infants go on to develop significant neu-romotor abnormalities and motor delays that signify CP, but most do not. Although neuromotor abnormalities tend to resolve or do not interfere with function, transient neuromotor abnormalities are associated with an increased risk of later school and behavioral problems (Drillien et al., 1980; Khadilkar et al., 1993; Sommerfelt et al., 1996; Vohr et al., 2005).

The severity of CP is determined by the type of CP, which limbs are affected, and the degree of functional limitation. Increasingly, investigators are distinguishing between mild CP and moderate to severe (i.e., disabling) CP (Doyle and Anderson, 2005; Grether et al. 2000; Vohr et al., 2005; Wood et al., 2000). Many longitudinal studies of the outcomes for preterm infants show good stability between motor assessments at 18 to 30 months of age and at school age (Hack et al., 2002; Marlow et al., 2005; Wood et al., 2000).

The smallest and most immature infants have the highest risk of CP. In their seventh report of CP in Sweden, Hagberg and associates (1996) reported an almost stepwise increase in the prevalence of CP with gestational age: 1.4 per 1,000 live births for children born at more than 36 weeks gestation, 8 per 1,000 live births for children born between 32 and 36 weeks gestation, 54 per 1,000 live births for children born between 28 and 31 weeks gestation, and 80 per 1,000 live births for children born at less than 28 weeks of gestation. Because they report prevalence as the number who have CP per 1,000 live births, infants who die are included in the denominator.

For the most immature infants, another meaningful statistic is the rate of CP among survivors. On the basis of data for preterm survivors born in the late 1980s through the 1990s, the rate of CP increases with decreasing gestational age or birth weight category (Table 11-1) (Colver et al., 2000; Cooke, 1999; Doyle et al., 1995; Doyle and Anderson, 2005; Elbourne et al., 2001; Emsley et al., 1998; Finnstrom et al., 1998; Grether et al., 2000; Hack et al., 2000, 2005; Hansen and Greisen, 2004; Hintz et al., 2005; Lefebvre et al., 1996; Mikkola et al., 2005; O'Shea et al., 1997; Piecuch et al., 1997a,b; Salokorpi et al., 2001; Sauve et al., 1998; Stanley et al., 2000; Tommiska et al., 2003; Vohr et al., 2000. 2005; Wilson-Costello et al., 2005; Wood et al., 2000). Only 0.1 to 0.2 percent of full-term children develop CP, whereas 11 to 12 percent born at

TABLE 11-1 Rates of Cerebral Palsy in Preterm Children by Gestational Age Category_

Rate of

Age Follow-up Number of Gestational Cerebral

TABLE 11-1 Rates of Cerebral Palsy in Preterm Children by Gestational Age Category_

Rate of

Age Follow-up Number of Gestational Cerebral

Study

Year(s) of Birth

(yr)

Rate (%)

Subjects

Age (wk)

Palsy (%)

Hintz et al., 2005"

1996-1999

1.8

87

473

<25

21

1993-1996

77

366

23

Vohr et al., 2005 "

1997-1998

1.8

84

716

<27

18

82

538

27-32

11

Vohr et al., 2005 "

1995-1996

1.8

84

910

<27

81

512

27-32

11

Vohr et al., 2005 "

1993-1994

1.8

74

665

<27

20

70

444

27-32

12

Mikkola et al., 2005

1996-1997

5

95

103

<27

19

Tommiska et al., 2003

1996-1997

1.5-2

100

5

22-23

20

18

24

11

34

25

12

47

26

11

Wood et al., 2000

1995

2.5

92

283

<26

88

2.2-

Emsley et al., 1998

1990-1994

6.1

100

40

23-25

18

Piecuch et al., 1997b

1990-1994

>1

95

18

24

9

30

25

20

Piecuch et al., 1997b

1990-1994

>1

95

38

26

11

Piecuch et al., 1997b

1990-1994

>1

95

94

24-26

13

Jacobs et al., 2000

1990-1994

1.5-2

90

274

23-26

15

Doyle et al., 2001

1991-1992

5

98

221

23-27

11

Finnstrom et al., 1998

1990-1992

3

98

362

23-24

14

25-26

10

>27

3

<1,000*

Lefebvre et al., 1996

1991-1992

1.5

85

9

24

11

24

25

25

Lefebvre et al., 1996

1991-1992

1.5

85

40

26

27

72

27

10

Lefebvre et al., 1996

1991-1992

1.5

85

72

28

17

217

24-28

17

"Birth weight (in grams) instead of gestational age is used.

"Birth weight (in grams) instead of gestational age is used.

27 to 32 weeks of gestation and 7 to 17 percent born at less than 27 or 28 weeks of gestation develop CP (Doyle, 2001; Elbourne et al., 2001; Finnstrom et al., 1998; Lefebvre et al., 1996; Vohr et al., 2005). A comprehensive British study of preterm infants born in 1995 with gestational ages of less than 26 weeks diagnosed CP in 20 percent of the survivors at 6 years of age (Marlow et al., 2005). In the few reported survivors with birth weights of less than 500 grams, a quarter to a half developed CP (Sauve et al., 1998; Vohr et al., 2000).

Many more studies have reported on the outcomes of CP in terms of birthweight categories. In a review of 17 studies published from 1988 to 2000, Bracewell and Marlow (2002) estimated that approximately 10 percent of preterm infants with birth weights of less than 1,000 grams developed CP. An older meta-analysis of 85 studies of infants with birth weights of less than 1,500 grams estimated that 7.7 percent of survivors developed CP (Escobar et al., 1991). Studies of 18- to 20-year-olds reported that from 5 to 7 percent of those who were born with birth weights of less than 1,500 grams and up to 13 percent of those born with birth weights of less than 1,000 grams had CP (Ericson and Kallen, 1998; Hack et al., 2002; Lefebvre et al., 2005; Saigal et al., 2006). A Swedish study of young men born as singletons from 1973 to 1975 with birth weights of less than 1,500 grams estimated an odds ratio for CP of 55 (95 percent confidence interval = 41 to 75) (Ericson and Kallen, 1998).

With continuing improvements in high-risk obstetric and neonatal intensive care over the last several decades, several studies have demonstrated small increases or decreases in the overall prevalence of CP (Colver et al., 2000; Hagberg et al., 1996; Stanley and Watson, 1992; Stanley et al., 2000). However, any improvements in gestational age- or birth weight-specific rates of CP are offset by dramatic decreases in the rates of infant mortality. The net result is that more preterm children survive, but more children have CP as well.

Many regional studies of children with CP find an overrepresentation of preterm children with CP than the number expected for their birth rates (Table 11-1) (Amiel-Tison et al., 2002; Colver et al., 2000; Cummins et al., 1993; Dolk et al., 2001; Hagberg et al., 1996; MacGillivray and Campbell, 1995; Petterson et al., 1993; Stanley and Watson, 1992). Although only 1.4 percent of infants are born at less than 32 weeks of gestation, they comprise 26 percent of children with CP. Four per cent of all live births are born at 32 to 36 weeks of gestation, and they constitute 16 to 37 percent of children with CP. Although less than 10 percent of births are preterm, approximately 40 to 50 percent of children with CP are born preterm.

Although children born preterm are vulnerable to all types of CP, the most common type is spastic diplegia (Hack et al., 2000; Hagberg et al., 1996; Wood et al., 2000). Spasticity is characterized by tight muscle tone, increased reflexes, and limited movement around one or more joints. Spasticity of both lower extremities but no or very little involvement of the arms constitutes spastic diplegia. Although most children with spastic diplegia require physical therapy and medical interventions (e.g., orthopedic surgery, orthoses, or Botulinum Toxicum injections), many children with spastic diplegia are quite functional by school age. In a study of children born at less than 26 weeks gestation, 43 percent with spastic diplegia were unable to walk and 43 percent had an abnormal gait at 6 years of age (Marlow et al., 2005).

A large regional study of Swedish preterm children with CP reported that 66 percent had spastic diplegia, 22 percent had spastic hemiplegia, and 7 percent had spastic quadriplegia (Hagberg et al., 1996). Associated deficits were common: 39 percent had mental retardation, 26 percent had epilepsy, 18 percent had severe visual impairment, and 23 percent had hydrocephalus. The proportion of children with CP who had spastic diplegia decreased with increasing gesta-tional age category: 80 percent for children born at less than 28 weeks of gestation, 66 percent for children born at between 28 and 31 weeks of gestation, 58 percent for children born at between 32 and 36 weeks of gestation, and 29 percent for children born at greater than 36 weeks of gestation. The proportion of children with hemiplegia increased with gestational age: 10 percent for children born at less than 28 weeks gestation, 16 percent for children born at between 28 and 31 weeks gestation, 34 percent for children born at between 32 and 36 weeks gestation, and 44 percent for children born at less than 36 weeks gestation.

Coordination and Motor Planning

Children with incoordination and motor planning problems are less likely to enjoy and participate in many preschool and playground activities. Minor neuromotor dysfunction is a diagnosis used to describe infants and children who have persistent neuromotor abnormalities but minimally to mildly impaired motor function. Children with minor neuromotor dysfunction may have mild motor delay but are able to walk by age 2 years and have good mobility. They have a higher risk of coordination difficulties, motor planning problems, fine motor incoordination, or sensorimotor integration problems (which at preschool and school age may be diagnosed as developmental coordination disorder) (Botting et al., 1998; Hadders-Algra, 2002; Hall et al., 1995; Khadilkar et al., 1993; Mikkola et al., 2005; Pharoah et al., 1994; Vohr and Coll, 1985). In a study of 5-year-olds born between 1996 and 1997 with birth weights of less than 1,000 grams, 51 percent had coordination problems, 18 to 20 percent had abnormal reflexes or abnormal posture, and 17 percent had exceptional involuntary movements (Mikkola et al., 2005). Sensorimotor integration problems can range from inability to tolerate certain textures of food or clothing (e.g., an inability to tolerate lumpy food or the tag on the back of a t-shirt) to difficulty following demonstrated directions (e.g., how to put on a shirt or tie their shoes) or an inability to tolerate motion (e.g., swinging).

Preterm children, even those with normal intelligence and no CP, have more difficulties than full-term children with fine motor, visual motor, visual perceptual, and visual spatial tasks. These tasks include drawing, cutting with scissors, dressing, writing, copying figures, perceptual mapping, spatial processing, finger tapping, and pegboard performance. In a study of 5-year-old children with birth weights of less than 1,500 grams, 23 percent had impaired fine motor skills and 71 percent scored 1 standard deviation or more below average on tests of fine motor function (Goyen et al., 1998). Below-average performances in visual motor skills and visual perceptual tasks were noted for 17 and 11 percent of the children, respectively. These problems were most common in children born at less than 28 weeks of gestation. Even the more mature preterm children are at risk for these problems; a third of school-age children born at 32 to 36 weeks of gestation had poor fine motor and writing skills (Huddy et al., 2001).

Failures at gross motor, fine motor, sensorimotor, and visual perceptual activities are mild in comparison with the difficulties with mobility and adaptive skills that many children with CP face. Nonetheless, these subtle abnormalities of central nervous system function can, over time, adversely influence the child's self-esteem and peer relationships, which in turn contribute to a cycle of frustration and despair that interferes with academic progress and social relationships. Early recognition of these subtle deficits allows modification of expectations, teaching methods, and the environment to support the development of these children and prevent adverse secondary consequences.

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