Infant Motor Assessment, Long-Term Clinical Outcome, Quantitative Cerebral MRI and Cognitive Training in Children Born Preterm with Very Low Birth Weight

Abstract

The preterm birth incidence and survival rates have been increasing over the last few decades due to advances in obstetric care and neonatal treatment. Despite this, the number of preterm children that develop severe neuroimpairments or more subtle difficulties within cognition, attention, behavioral and every day skills are still high. Perinatal brain injury, including diffuse and focal white matter necrosis and grey matter injury is the most common cause of the neuroimpairments in preterm children. The suggested term “encephalopathy of prematurity” indicates that preterm brain injury is a complex injury in the developing brain that has secondary consequences regarding maturation and development, most likely of the whole brain.

Studies report that the difficulties preterm children have impact scholastic achievement and academic performance, and therefore early identification of impairments is essential in order to initiate early intervention strategies as soon as possible. An observational method of infant’s spontaneous movements at 14 weeks post term age: The General Movement Assessment (GMA) has been shown to be a valuable predictor of development of later cerebral palsy (CP) in preterm and high-risk term-born children. Recently researchers suggested that a detailed analysis of the motor repertoire that is included in the general movement assessment also can identify non-CP children with motor and cognitive deficits. In order to examine the predictive value of the general movement assessment in high-risk children that do not develop CP and to examine long-term outcome with a special focus on the extremely low birth weight (ELBW) children without CP, we initiated a study including 40 high-risk term-born and preterm children at 10 year age and a control group consisting of 33 age matched healthy children. An extensive assessment of motor, cognition, executive function, attention and behavior was performed at 10 years follow-up. In addition to this we also performed a cerebral MRI in the ELBW children as well as in the controls. Videotapes of the high-risk children that had been filmed 10 years ago were assessed with the GMA and a detailed assessment of the infant motor repertoire shortly before the follow-up examination. We found that the assessment of GMA and motor repertoire was predictive for CP and a composite of cognitive and motor deficits in high-risk children without CP. When comparing non-CP ELBW children with controls we found similar IQ and neuropsychological test results but lower working memory skills, poorer motor skills, and more attention and behavioral problems in the non-CP ELBW children. On MRI we found smaller total brain volumes, reduced volumes of globus pallidus, cerebellar white matter, corpus callosum and regionally reduced cortical surface area in the non-CP ELBW children. The inferior clinical test results and reduced brain volumes were mostly found in the non-CP ELBW children with abnormal early motor repertoire. This may indicate that the early motor assessment can be a valuable predictor in preterm children who do not develop CP but still are at a high risk of developing composite neuroimpairments. By successfully identifying these children, early intervention can be initiated and this might reduce the risk of later academic or social difficulties.

The second aim of this thesis was to investigate whether a computerized working memory training program could have positive effect in preterm-born preschoolers. Working memory has been defined as our ability to temporarily store and at the same time manipulate information “online” over short periods of time. Working memory is considered a prerequisite for other executive functions that are essential for a child’s ability to learn, plan their actions, solve problems, and develop language as well as mathematical skills. When working memory skills are impaired, learning difficulties with lasting effects into adolescence and adulthood may result. Studies indicate that working memory can be trained and positive effects of a computerized working memory training program have been shown in children with ADHD, Downs syndrome, in children after chemotherapy, and in ELBW adolescents. We included 20 very low birth weight (VLBW) children that trained with the Cogmed JM program designed for preschool aged children, 10-15 minutes a day, 5 days a week over a 5- week period. The children were examined with an extensive cognitive and neuropsychological test battery before and 4 weeks after training. We found that the VLBW preschoolers had positive short-term effects on trained and non-trained working memory tasks, and transfer effects were observed as improvement on auditory attention, phonological awareness, and visual as well as verbal memory. In order to examine whether the intervention had long-term positive effect after 7 months, we included a group of age-matched non training VLBW children. We found performance gain on non-trained visual working memory tasks and on tests of visual and verbal memory and learning, compared with VLBW controls who had not trained. We concluded that this intervention might be valuable in preterm children before they start school and that such interventions might prevent or at least reduce cognitive problems that impact educational achievement and social function. However, larger studies must be conducted to confirm our results before general recommendations can be made with regard to implementing such training in clinical practice.