Developmental Coordination Disorder

Abstract

For the last 100 years, poor motor coordination in children has been recognized as a developmental problem.1 As early as 1937, these children were classified as “clumsy.”1 Since then, other terms such as “motorically awkward,” “motor impaired,” and “physically awkward” have been used to describe these children, and the terms “developmental apraxia” and “perceptual motor difficulties” have been used to characterize this developmental problem.2,3 Since the 1994 International Consensus Conference on Children and Clumsiness, the term “developmental coordination disorder” (DCD) has been used to describe the condition of children with motor incoordination.1,4 The purpose of this article is to provide the following information about DCD: (1) definition, (2) prevalence, (3) etiology, (4) discussion regarding the difficulties in classifying these children, (5) common characteristics, (6) long-term prognosis, and (7) brief review of treatment approaches. Developmental coordination disorder, a chronic and usually permanent condition found in children, is characterized by motor impairment that interferes with the child's activities of daily living and academic achievement.3,5 In order for a child to be diagnosed with DCD, these motor impairments must negatively affect some other aspect of his or her life.6 Impairment alone, however, does not qualify a child for the diagnosis of DCD; the motor impairment must not be caused by or have the symptoms of an identifiable neurological problem.2,5 That is, the child must not have any disturbances of muscle tone (ataxia or spasticity), sensory loss, or involuntary movements. If mental retardation is present, the testable IQ of the child must be greater than 70 and the motor impairments must be greater than what would normally be expected for children with mental retardation.5 Finally, a child diagnosed with DCD must not meet the criteria for a diagnosis of pervasive developmental disorder.6 Developmental coordination disorder appears to be a fairly common disorder of childhood and is usually identified in children between 6 and 12 years of age. Ten years ago, researchers7,8 estimated that DCD occurred in 10% to 19% of school-aged children. With a more precise definition of DCD, the current prevalence is estimated to be between 5% and 8% of all school-aged children,5,9–11 with more boys than girls (2:1) being diagnosed with DCD.12 This difference may reflect higher referral rates for boys, because the behavior of boys with motor incoordination may be more difficult to manage at home and in the classroom.8 In addition, a higher incidence of DCD may be found among children with a history of prenatal or perinatal difficulties.3 Due to the heterogeneity of DCD, finding its cause has been difficult.3 Several theories speculate that the etiology of DCD is part of the continuum of cerebral palsy5,13; is secondary to prenatal, perinatal, or neonatal insult3; or is secondary to neuronal damage at the cellular level in the neurotransmitter or receptor systems.14 Hadders-Algra14 based her view that DCD is a result of damage at the cellular level on evidence that cerebral palsy is often caused by prenatal damage that cannot be identified by current diagnostic techniques. Developmental coordination disorder, a chronic and usually permanent condition found in children, is characterized by motor impairment that interferes with the child’s activities of daily living. Although both standard and nonstandard functional tests are available to identify the specific disabilities experienced by a child with DCD, relating the observed disabilities to the primary impairment(s) or any possible neuropathology is not easily accomplished. The problems experienced by children with DCD are believed to emanate from abnormalities in neurotransmitter or receptor systems rather than from damage to specific groups of neurons or brain regions.15 Children's difficulties with coordination can result from a combination of one or more impairments in proprioception, motor programming, timing, or sequencing of muscle activity. A number of theories have evolved in an attempt to shed light on the specific neuronal processing deficits that contribute to DCD. Current models used to explain the neural regulation of posture and movement during development can serve as a basis for the examination and management of individuals with DCD. Using these models, many of the deficits of motor control observed in these children can be described. A variety of theoretical models exist to explain the role of the nervous system in motor development. Forty years ago, the primitive reflex model was a generally accepted theory used to explain how the brain regulates early motor behavior.16 As development proceeded, the higher centers exerted increasing control over the lower reflexes.16 These earlier models were based on a hierarchy of motor control in which higher centers were capable of planning and executing a motor plan without external or