Infants born preterm and with a very low birthweight demonstrate, on average, significant motor impairment persisting throughout childhood [1
]. The presence of additional perinatal complications, such as perinatal brain injury or bronchopulmonary dysplasia (BPD), lowers standard scores on tests of motor development by half a standard deviation (SD) more [1
Cerebral palsy (CP) in preterm infants is typically caused by white matter injury (WMI). WMI includes conditions such as intraventricular hemorrhage (IVH), periventricular hemorrhagic infarction, periventricular leukomalacia (PVL), and diffuse or focal noncystic injury [1
]. Both sensory and motor pathways may be affected in these lesions [5
]. The incidence of CP in children with severe WMI ranges from 50–85% [4
]. These rates of CP compare with an incidence of 5–10% in all premature infants. Also common are cognitive and behavioral deficits affecting school performance in 25–50% [2
]. In Illinois and other US states, children with perinatal brain injury are automatically eligible for early intervention services because of the recognized risk of poor developmental outcome associated with these lesions.
In addition to an increased risk of CP, numerous researchers have demonstrated a high incidence of atypical motor development in children with periventricular brain injuries. Kicking has altered characteristics in these children [6
], and the quality of spontaneous kicking is related to age at walking in preterm infants [10
]. Jeng and colleagues [11
] showed a delay in onset of walking in children with WMI, which occurred on average at 14 months corrected age (CA). Hadders-Algra [12
] identified a reduction of movement complexity and variability as a characteristic result of periventricular brain injuries, and Barbosa and colleagues [13
] reported both delayed motor development and regressions in leg movements in infants such as these who were later diagnosed with CP. Specifically, infants who later developed CP were found over the course of monthly assessments through 4 months CA to regress in their ability to hold their legs in antigravity positions in supine and to perform spontaneous kicking movements with legs off the supporting surface [15
Despite the high risk for poor motor outcome of children with periventricular brain injury, few studies have asked the question of whether intervention can alter outcomes. In fact, studies of early intervention for infants at high risk for motor dysfunction tend to show no or very limited treatment effects [16
]. Of those with positive outcomes in the early weeks or months, sustained improvements have not yet been demonstrated by study of longer-term outcomes [19
]. Questions that need addressing include whether it is possible to reduce the delay in motor development or the severity of CP in those who have sustained a permanent brain injury.
Because of the abundant descriptions of impaired leg movements in this population and the lack of research on the efficacy or effectiveness of early physical therapy to improve outcomes, this project was designed as a randomized, multi-institutional, and multidisciplinary pilot study of the effects of a home exercise intervention on motor function of preterm infants with periventricular brain injury. The overall objective was to:
Determine whether kicking and treadmill stepping intervention added to usual physical therapy beginning at 2 months CA improves motor function at 12 months CA in children with periventricular brain injury, as compared with outcomes of a control group receiving only usual physical therapy as prescribed by their personal caregivers.
The intervention program for this study was designed to address the regressions and delays in kicking and walking demonstrated by previous research and to supplement typical physical therapy by providing a program of task-specific activities [23
] for lower extremity training in supine, sitting, standing, and walking. The theoretical basis of the program emphasized self-initiated movements in response to the presentation of attractive, commercially available toys. Success in contacting toys with the feet was expected to result in feedback for learning while providing exercise for strengthening leg muscles, developing endurance for physical activity, and stimulating development of anticipatory postural control in the head and trunk [24
]. Use of different toys across the first year was intended to provide novelty to sustain the interest of the children and to encourage regular practice of leg movements in increasingly more demanding postural positions. In addition to kicking exercises, the program included treadmill stepping based on the successful application of this method for lowering the age at attainment of walking in children with Down syndrome [28
] and a case report on treadmill training in an infant with WMI [29
We hypothesized that infants receiving the early intervention program aimed at leg movements and locomotor performance would walk independently at an earlier age and would have better quality of movement and motor development at 12 months CA than infants receiving conventional physical therapy alone.