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INTRODUCTION

In this chapter, we focus on two broad categories of developmental disorder—motor disorders and communication disorders. For each, the diagnostic criteria set forth in the International Statistical Classification of Diseases and Related Health Problems—10th Revision (ICD-10) are outlined in the sections below. Our coverage goes beyond that, however, and will incorporate discussion of a broader range of conceptual issues, empirical findings, and diagnostic considerations relevant to each of these categories of disorder.

MOTOR DISORDERS

ESSENTIALS OF DIAGNOSIS ICD-10 Diagnostic Criteria for Specific Developmental Disorder of Motor Function

Specific Developmental Disorder of Motor Function (F82) is defined as:

  • A disorder in which the main feature is a serious impairment in the development of motor coordination that is not solely explicable in terms of general intellectual disability or of any specific congenital or acquired neurological disorder

  • There are neurodevelopmental immaturities such as choreiform movements of unsupported limbs, or mirror movements and other associated motor features, as well as impaired fine and gross motor coordination

The classification includes:

  • Clumsy child syndrome

  • Developmental coordination disorder

  • Developmental dyspraxia

Exclusions:

  • Abnormalities of gait and mobility (R26)

  • Lack of coordination (R27)

Adapted with permission from the World Health Organization (WHO): International statistical classification of diseases and related health problems. 10th revision, Fifth edition, 2016. Geneva: World Health Organization.

The ICD-10 criteria for Specific Developmental Disorder of Motor Function. This category includes Clumsy child syndrome, Developmental coordination disorder, and Developmental dyspraxia. Other conditions, such as stereotyped movement disorders, tic disorders, and Tourette's disorder, are also touched on briefly later.

General Considerations

A. Epidemiology

It is estimated that 6% of schoolchildren have developmental coordination disorder. It is about four times more common in boys than in girls. General prevalence estimates on stereotyped movement disorder are lacking, but it is more common in boys and among children with intellectual disability.

B. Etiology

Motor development involves the gradual acquisition of central control over reflex movement. There is controversy over whether this acquisition involves the suppression of the reflexes 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 allows the modification of timing, speed, force, and direction of movement until the desired endpoint is achieved. Initially, movements are clumsy, as the child struggles ...

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