Developmental coordination disorder: A review and update (2012) - Zwicker et. al. - Article

Summary of the article: Developmental coordination disorder: A review and update (2012) - Zwicker et. al.

Developmental Coordination Disorder (DCD) is heterogeneous, with some children experiencing difficulties only with fine motor skills, others only with gross motor skills and some with both. DCD is not due to a neurological disorder or delayed cognitive development, and thereby is more than just the lower end of normal variance in motor abilities.

Formerly, there was a lot of discordance about defining the symptoms of DCD. Several terms have been used to describe children with motor difficulties such as clumsy child syndrome and physical awkwardness. To improve communication among clinicians and researchers, an international consensus meeting was held, eventually agreeing on the term DCD.

Prevalence rates of DCD vary from 1,4% to 19%, but the most commonly reported prevalence is 5-6%. The varying prevalence rates can be partly explained because of the differences in identifying DCD. Some studies also include children who experience motor difficulties without quantifying for intelligence or the impact on activities in daily life. On the other hand, DCD may be underreported because of the lack of knowledge and awareness of the disorder. Most clinical studies have shown much higher prevalence rates among boys, though recent research indicated a more modest ratio as in 1,9:1 or almost equal gender distribution. Differences in prevalence rates among boys and girls may be due to the fact that DCD is more prevalent in children born preterm or with very low birth weight, whereas several studies have shown that neurological outcomes are more adverse in male infants born preterm than in females.

So fat there is little information about the aetiology of DCD, though it may be related to central nervous system pathology. Therefore DCD was first conceptualized as a form of minimal brain dysfunction (MBD) and later on as the more complex minimal neurological dysfunction (MND). It is suggested that MND would be related to preterm birth. Other propositions about the aetiology of DCD relate to an atypical brain development. Diffuse rather than specific areas of the brain may be involved, thus children may have one or more disorders depending on the extent of disruption to brain development.

Two mechanisms underlying DCD have been hypothesized. First, the automatization deficit hypothesis states that children with DCD might experience difficulties with making motor skills automatic. Thereby it suggests the involvement of the cerebellum. Also suggesting cerebellar involvement is the internal modeling deficit hypothesis , which suggests that successful motor control is the result from an internal model that predicts sensory consequences of motor command. The cerebellum would provide information about the discrepancy between predicted movement and actual movement, and giving error signals as feedback if there is a mismatch.

DCD often co-occurs with other developmental disorders such as ADHD, learning disabilities and speech or language impairment. They experience self-care challenges and difficulties with school-related tasks in everyday life, their leisure participation may be impacted and they may have to deal with impairments considering participation in physical education. They can also experience significant secondary emotional and mental health concerns. The motor problems caused by DCD persist into adulthood., though outcomes can be improved by interventions delivered by therapists, parents and teachers.

Interventions can be broadly categorized into two types. First is deficit oriented approaches, which includes sensory integration therapy, sensorimotor-oriented therapy and process-oriented therapy. This intervention is targeted at the underlying process deficit, with remediation of the deficit resulting in improved task performance. Unfortunately, this approach is based on outdated research and inconclusive evidence for its effectiveness. Second, task specific approaches include task-specific intervention, neuromotor task training, ecological intervention and Cognitive Orientation to daily Occupational Performance (CO-OP). This approach is grounded in current theories and evidence for its effectiveness is promising. Nevertheless, no single approach has been fully substantiated by research. Some researchers, such as Wilson, have argued to examine brain-behavior interactions using a cognitive neuroscientific approach to better understand motor learning in children with DCD.

Imaging studies using fMRI show that children with DHD seem to have dysfunction in the attentional brain network as evidenced by lower activation in the dorsolateral prefrontal cortex compared to control children. They also show under-activation in relative brain areas during a motor learning paradigm, whereas they show greater brain activity during motor performance. The writers of this article believe it to be necessary to use neuroimaging techniques in order to inform clinician scientist on how interventions shape patterns of brain activity and lead to improved function, so that clinical practice can be advanced.