Chapter 33. Motor Skills Disorder & Communication Disorders

Essentials of Diagnosis

DSM-IV-TR Diagnostic Criteria

1. Performance in daily activities that require motor coordination is substantially below that expected given the person's chronological age and measured intelligence. This may be manifested by marked delays in achieving motor milestones (e.g., walking, crawling, sitting), dropping things, “clumsiness,” poor performance in sports, or poor handwriting.

2. The disturbance in Criterion A significantly interferes with academic achievement or activities of daily living.

3. The disturbance is not due to a general medical condition (e.g., cerebral palsy, hemiplegia, or muscular dystrophy) and does not meet criteria for a pervasive developmental disorder.

4. If mental retardation is present, the motor difficulties are in excess of those usually associated with it.

(Reprinted, with permission, from Diagnostic and Statistical Manual of Mental Disorders, 4th ed. Text Revision Copyright 2000 American Psychiatric Association.)

General Considerations

Recent research suggests that developmental coordination disorder can be divided into several subcategories (Table 33–1).

Epidemiology

It is estimated that 6% of schoolchildren have developmental coordination disorder. Children with perceptual motor defects have a high incidence of educational problems and psychological maladjustment.

Etiology

Motor development involves the gradual acquisition of central control over reflex movement. There is controversy over whether this acquisition involves the suppression of reflex and spontaneous cyclic movements of early infancy or whether infantile movements are incorporated into the elements that become voluntary motor skills.

Skilled movement requires a program of action with a specified objective or set goal. The program is composed of a sequence of hierarchically organized subroutines under executive control. Once acquired, motor skills are flexible. For example, the child who has learned to walk can do so on smooth, rugged, soft, or hard surfaces. The adaptation to different situations of the programmed subroutines requires accurate perception, central processing, executive control, and progressive feedback. Feedback monitors the approximation of the program to the set goal and modifies the timing, speed, force, and direction of movement until the desired endpoint is achieved. Initially, feedback produces jerky movements, as the child struggles to master the skill. Eventually, the skill is regulated centrally and the subroutines automated. A variety of skills ...