Clinical presentation

Learning disabilities are not a singular disorder but a group of varied and often multidimensional disorders. Difficulties in learning may manifest themselves in various combinations of impairments in language, memory, visual-spatial organization, motor function, and the control of attention and impulses. ^, The characteristics of a child with a learning disability are often diverse and complex. Each child presents a different composite of system problems/impairments and functional deficits, preventing participation in activities and societal limitations. Table 12.1 summarizes some of the clinical and behavioral manifestations in children with learning disabilities.

The most commonly recognized performance difficulties in learning are associated with academic success. Fletcher and colleagues argued that learning disabilities should be characterized as “unexpected” because the child is not learning up to expectations despite adequate instruction. Typically, the areas of deficits are observed in verbal learning, including difficulties with reading, the acquisition of spoken and written language, and arithmetic. Impairments in nonverbal learning are equally important and more recently recognized. The three primary areas affected by nonverbal learning disorders include visual-spatial organization, social-emotional development, and sensorimotor performance. Accompanying behavioral manifestations may include problems with self-regulatory behaviors, such as lack of attention, hyperactivity, and poor impulse control. Difficulties in social perception and social interactions may also be observed. ^, These learning and behavioral difficulties may be isolated (e.g., academic, motor, or behavioral), combined (e.g., academic and motor), or global (academic, motor, and behavioral). In addition to verbal and nonverbal disabilities, specific motor impairments also can be present and affect academic achievement or daily life tasks. ^,

Definition

The heterogeneity of persons with learning disabilities has made consensus on a single definition difficult. Many disciplines describe learning disabilities according to their own frames of reference. Medical professionals tend to relate the deficit to its cause, particularly to cerebral dysfunction. Terms historically used include brain injured, minimal brain dysfunction, and psychoneurological disorder, all implying a neurological cause for the deviation in development. However, educational professionals prefer to describe the child’s difficulties in behavioral or functional terms. Educators view children with learning disabilities as “children who fail to learn despite an apparently normal capacity for learning.” Current terminology within the academic environment includes reading disorder, mathematics disorder, disorder of written expression, and intellectual disabilities. ^, The lack of consensus for one accepted definition continues to affect consistency in diagnosis, research, and intervention for persons with learning disabilities.

After multiple revisions, the National Joint Committee on Learning Disabilities (NJCLD), which represents several professional organizations, proposed the following definition:

Learning disability is a general term [for a condition] that:

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  Is intrinsic to the individual . . . [the term] refers to a heterogeneous group. (Each individual with learning disabilities presents with a unique profile of strengths and weakness.)

  
  
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  Results in significant difficulties in the acquisition and use of listening, speaking, reading, writing, reasoning, or mathematical abilities. (These difficulties are evident when appropriate levels of effort by the student do not result in expected performance, even when provided with effective instruction.)

  
  
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  Is presumed to be due to central nervous system dysfunction and may occur across the life-span. (They persist throughout life and may change in their presentation and severity at various stages of life.)

  
  
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  May occur concomitantly with other impairments or other diagnoses. (For example, difficulties in self-regulation and social interaction may exist separately or result from the learning disability. Individuals with attention-deficit disorders, emotional disturbances, or intellectual disabilities may experience learning difficulties, but these diagnoses do not cause or constitute them.)

  
  
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  Is not due to extrinsic factors. (Such as insufficient or inappropriate instruction, or cultural differences.)

This definition identifies a proposed cause but does not provide a clear exclusion statement regarding what learning disabilities may not result from. A positive component of this definition is the lifelong nature of the condition. In addition, by including the behavioral manifestations of regulatory and social difficulties, a more complete picture of functional problems for the individual with learning disabilities is presented. This could assist in the creation of more comprehensive and life-spanning programs of service and ultimately help in the recognition and remediation of functional and societal limitations.

The definition used in educational settings was initially passed in Public Law 94-142 and later incorporated into the Individuals with Disabilities Education Act (IDEA) (Section 602.26).

Children with learning disabilities are defined by IDEA as follows:

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  Individuals with a disorder in one or more of the basic psychological processes involved in understanding or using spoken or written language. (This emphasizes the receptive and expressive difficulties a student may demonstrate.)

  
  
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  Those who are experiencing difficulties in the ability to listen, think, speak, read, write, spell, or do mathematical calculations. (These highlight the academic difficulties the student may experience.)

  
  
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  Those who may have conditions such as perceptual disabilities, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia.

  
  
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  Those who have a learning problem that does not result from other disabilities such as motor deficits, emotional disturbances, or environmental, cultural, or economic differences.

This description does not specifically address cause but does highlight psychological processes versus neurological impairments. The primary disability focus is on language, which may exclude difficulties in learning that involve nonverbal reasoning. This definition does not mention regulatory, reasoning, and social perception difficulties that may contribute to understanding the student’s complete profile. On a foundational level, this definition formed the basis for creating academic programs and delineating appropriate services for children with learning disabilities.

IDEA mandates that all children will have free and appropriate education and authorizes aid for special education and educationally relevant services for children with disabilities. IDEA influences how children with learning disabilities are identified and classified. The 1997 amendments of IDEA, by promoting the early identification and provision of services, redirected the focus of special education services by adding provisions that would enable children with disabilities to make greater progress and achieve higher levels of functional performance.

The IDEA 2004 amendments eliminate a previous requirement that students must exhibit a severe discrepancy between intellectual ability and achievement for eligibility. This “severe discrepancy” policy often mandated that children would have to experience failure for several years to demonstrate the requisite degree of discrepancy. The current goal is to identify ways of serving students more quickly and efficiently once they begin to show signs of difficulty. Congress also indicated specifically that (1) intelligent quotient (IQ) tests could not be required for the identification of students for special education in the learning disabilities category and (2) states had to allow districts to implement identification models that used Response to Instruction (RTI). The RTI models suggest that the learning difficulty may be intrinsic to the child, inherent in the instruction, or a combination of both. The models propose systematically altering the quality of instruction and repeatedly measuring the child’s response to that instruction. Inferences can then be made about the child’s deficits contributing to learning difficulties.

IDEA 2004 also limits the schools from finding a student eligible for special education services if the learning problems are determined to be caused by a lack of appropriate instruction. The law currently encourages schools to use scientific, research-based interventions to maximize a student’s opportunity for success in the general education setting (least restrictive environment [LRE]) before being placed in special education. IDEA encourages educators to stress the importance of identifying individual differences and patterns of ability within each child and adjust the educational methods accordingly. Academic achievement relies heavily on the effectiveness of the teacher and the instructional techniques. Studies indicate that learning disabilities do not fall evenly across racial and ethnic groups, with a higher incidence of special education services needed for black, non-Hispanic children. The No Child Left Behind (NCLB) Act challenges states and school districts to become more accountable for improving educational standards by intensifying their efforts to close the achievement gap between underachieving students and their peers.

In 2015 the Every Student Succeed Act (ESSA) replaced the NCLB. By law, ESSA requires state plans to include a description of how the state will implement the following ^, :

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  Academic standards

  
  
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  Annual testing

  
  
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  Goals for academic achievement

  
  
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  Ways that schools will be held responsible for student achievement

  
  
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  Plans for supporting and improving struggling schools, including professional development for educators and support for English learners

Despite the ESSA mandate, a systematic analysis by the NCLD has found that groups of students, including students with disabilities, low-income students, and students learning English, are frequently neglected .

Classifications

The two most widely used classification systems are those of the American Psychiatric Association (APA) ( Diagnostic and Statistical Manual of Mental Disorders [DSM]) and the World Health Organization (WHO) (International Classification of Diseases [ICD]). Educational professionals prefer the DSM classification for its academic relevance. A variety of specific academically related disorders are outlined in the DSM. The latest edition, DSM-V, defines specific learning disorders (SLDs; often referred to as learning disorder or learning disability; see note on terminology) as a neurodevelopmental disorder that begins during school age, although may not be recognized until adulthood. Learning disabilities refers to ongoing problems in one of three areas, reading, writing, and math, which are foundational to one’s ability to learn.

The classification system commonly used by therapists is the ICD. The ICD codes are state-mandated diagnostic codes used for billing and information purposes. In the recently revised ICD-11, learning disability is categorized under a “Mental, Behavioral, and Neurodevelopmental disorder.” Specifically, learning disability is labeled as a developmental learning disorder and is “characterized by significant and persistent difficulties in learning academic skills, which may include reading, writing, or arithmetic.” In addition, ICD-11 describes developmental learning disorders as “not due to a disorder of intellectual development, sensory impairment (vision or hearing), neurological or motor disorder, lack of availability of education, lack of proficiency in the language of academic instruction, or psychosocial adversity.”

Incidence and prevalence

In the United States the National Center for Learning Disabilities reported that 1 in 5 children has learning and attention issues and 1 in 16 children will have Individualized Educational Plans (IEPs) for specific learning disabilities. From this subset, it has been reported that in fourth grade, 27% without disabilities, 69% with disabilities, and 85% with specific learning disabilities fall below basic levels of literacy. In 2015 to 2016, the number of students aged 3 to 21 receiving special education services was 6.7 million, or 13% of all public school students. Among students receiving special education services, 34% had specific learning disabilities.

Perspectives on the causes of learning disabilities

Learning disability is a diverse diagnosis with varied manifestations; therefore searching for a single cause would be inadequate. Historically, researchers have studied causative factors including (1) brain damage or dysfunction caused by birth injury, perinatal anoxia, head injury, fetal malnutrition, encephalitis, and lead poisoning; (2) allergies; (3) biochemical abnormalities or metabolic disorders; (4) genetics; (5) maturational lag; and (6) environmental factors, such as neglect and abuse, a disorganized home, and inadequate stimulation.

Current sources agree that possible causes of learning disabilities can include problems with pregnancy and birth (e.g., drug and alcohol use, low birth weight, anoxia, and premature or prolonged labor) and incidents occurring after birth (e.g., head injuries, nutritional deprivation, and exposure to toxic substances such as lead). Genetic and hereditary links also have been observed, with learning difficulties often seen across generations within families. The emotional and social environment have also been considered as a contributing factor to learning disabilities.

Children with learning disabilities frequently display a composite of neuropsychological symptoms that interfere with the ability to store, process, or produce information. These symptoms typically include disorders of speech, spatial orientation, perception, motor coordination, and activity level. Researchers have attempted to identify areas of the brain that may be responsible for these functional limitations. Tools being used include empirical measures of physiological function such as electroencephalography, event-related potentials (ERPs), brain electrical activity mapping (BEAM), regional cerebral blood flow (rCBF), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI). These measures expand the understanding of brain functioning but are best used in conjunction with data on functional and behavioral manifestations.

Research findings on brain structure have documented that certain functions are specialized within each hemisphere, and this specialization is optimal for efficient learning. ^, The left hemisphere processes information in a sequential, linear fashion and is more proficient at analyzing details. Academically, this hemisphere is responsible for recognizing words and comprehending material read, performing mathematical calculations, and processing and producing language.

The right hemisphere processes input in a more holistic manner, grasping the overall organization or the “gestalt” of a pattern. ^, This type of organization is advantageous for spatial processing and visual perception. Functionally, the right hemisphere synthesizes nonverbal stimuli, such as environmental sounds and voice intonation, recognizes and interprets facial expressions, and contributes to mathematical reasoning and judgment. Over time these differences in left and right brain processing have become accepted and are commonly labels of cognitive style (i.e., left-brained versus right-brained learner).

A strict left-right dichotomy is oversimplified because it does not take into account many aspects of functional brain organization. ^, Both hemispheres must work together for a variety of specific academic outcomes such as reading and mathematical concepts. In addition to the communication that occurs between the hemispheres via the corpus callosum, essential communication within the hemispheres is also present. Intrahemispheric communication is critical for developing higher level cognitive functions such as memory, language, visual-spatial perception, and praxis. Research suggests that children with learning disabilities show different patterns of cerebral organization than normal children. ^, However, brain plasticity is the basis for designing and implementing a variety of intervention techniques aimed at improving processing.

Subgroups

In early attempts to classify learning disabilities, Denckla and Rudel determined that approximately 30% of the 190 children they assessed by neurological examination could be classified into three recognizable subgroups. The other 70% exhibited an unclassifiable mixture of signs. Of the 30%, the first subgroup was classified as children having a specific language disability. These children, who were failing reading and spelling, showed a pattern of inadequacy in repetition, sequencing, memory, language, motor, and other tasks, all of which require rote functioning. The second group had a specific visual-spatial disability. These children had average performance in reading and spelling with delayed arithmetic, writing, and copying skills. The children in this subgroup all had social and/or emotional difficulties. The third group manifested a dyscontrol syndrome. These children had decreased motor and impulse control, were behaviorally immature, and were average in language and perceptual functioning.

Grouping children with learning disabilities based on patterns of academic strengths and weakness is as important as grouping them based on neuropsychological or cognitive measures. With an academic classification the heterogeneity of learning disabilities can be more clearly recognized and learning modalities can be adjusted to the individual child. For example, a child with a specific reading difficulty could be experiencing deficits in word recognition, fluency, or comprehension. Through identification of the specific areas of weakness in reading, intervention can be individualized to improve academic performance.

Based on historical and current trends the following general subgroups will be explored: verbal learning impairments, nonverbal learning disabilities (NVLDs), motor coordination deficits, and social and emotional challenges.

Social and emotional challenges

Behavioral patterns or disorders associated with learning disabilities include frustration, anxiety, depression, attention deficits, conduct problems, and global behavior problems. Ames stressed that no single behavior pattern is prevalent in children with learning disabilities. Children with learning disabilities not only struggle in the classroom but experience difficulties in the social arena as well. Issues in learning and related behaviors affect one another in a complex manner, leaving us to wonder which is the cause and which is the symptom.

Frustration, deflated self-esteem, and other social and emotional difficulties tend to emerge when instruction does not match learning styles. This frustration mounts as the child notices classmates surpassing them, and this often results in exasperation with trying to keep up. The pressure then becomes for the child to “try harder,” when ironically most do not understand just how hard the child is trying. The dissatisfaction in not meeting the teacher’s expectations is often overshadowed by the inability to succeed in personal goals and a lack of self-worth. This can result in the development of internal perfectionism to deal with the lack of competence, with the belief of the child that he or she should not make mistakes.

Anxiety is another response that may occur with persistent difficulties in understanding and successfully completing schoolwork. This occurs when the child feels out of control and lacks the ability to plan and execute strategies for success. The mismatch between ability, expectations, and outcomes can cause frustration, disappointment, and stress, triggering a range of emotions and behaviors that interfere with everyday functioning in multiple environments.

Other emotional difficulties are noted in attention. When a lesson is taught in a manner that is too complex, the child may become inattentive. Attention problems can influence behavior, often relating to difficulties with impulse control, restlessness, and irritability, affecting learning and peer interactions. These issues frequently coincide with frustration, anger, and resentment, which may manifest as a conduct problem (e.g., verbal and nonverbal aggression, destructiveness, and significant difficulties interacting with peers). Children with learning disabilities often become discouraged and fearful, are less motivated, and develop negative and defensive attitudes. These patterns of behavior can worsen with age, contributing to juvenile delinquency. Low self-esteem and depression are common during school years and tend to escalate around age 10 years.

Poor academic progress, additional prompting needed from teachers, and negative attention for disruptive behaviors can cause children with learning disabilities to perceive themselves as being “different.” Lack of success in school experiences can influence the development of positive self-perception and can have powerfully negative effects on self-esteem. A self-defeating cycle may be established: the child experiences learning problems, school and home environments become increasingly tense, and disruptive behaviors become more pronounced. These responses, in turn, further affect the child’s ability to learn. Lack of success generates more failure until the child anticipates defeat in almost every situation.

Assessment and intervention

Definition

The DSM-5 classifies DCD as a discrete motor disorder under the broader heading of neurodevelopmental disorders. The specific DSM-5 criteria for DCD are as follows:

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  Acquisition and execution of coordinated motor skills are below what would be expected at a given chronological age and opportunity for skill learning and use; difficulties are manifested as clumsiness (e.g., dropping or bumping into objects) and as slowness and inaccuracy of performance of motor skills (e.g., catching an object, using scissors, handwriting, riding a bike, or participating in sports).

  
  
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  The motor skills deficit significantly or persistently interferes with ADLs appropriate to the chronological age (e.g., self-care) and impacts academic or school productivity, prevocational and vocational activities, leisure, and play.

  
  
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  The motor skills deficits cannot be better explained by intellectual disability or visual impairment and are not attributable to a neurological condition affecting movement (e.g., cerebral palsy, muscular dystrophy, or a degenerative disorder).

Clinical presentation

DCD is a childhood disorder characterized by poor coordination and clumsiness. Typically, there is no easily identifiable neurological disorder accompanying this lack of motor skills required for everyday life. Characteristics can be seen in developmental areas such as gross motor, fine motor, visual motor, self-care, and social-emotional areas. Children tend to develop at a slower rate and require more effort and practice to accomplish age-level tasks. The salient features are coordination difficulties that include decreased anticipation, speed, reaction time (RT), and quality and grading of movement. ^, These children often have difficulties analyzing the task demands of an activity, interpreting cues from the environment, using knowledge of past performance, and transferring and generalizing skills.

Coordination difficulties are most apparent when complex motor activities are attempted. Physical education class often presents major problems. For example, a 9-year-old boy described his motor problems as follows: “When the gym teacher tells us to do something, I understand exactly what he means. I even know how to do it, I think. But my body never seems to do the job.”

Development of gross and fine motor skills, coupled with the child’s ability to master body movements, enhances feelings of self-esteem and confidence. Through persistence in mastering the varied challenges of motor exploration the child builds self-reliance. The frustrations and accomplishments enhance confidence and the ability to take risks. By engaging in group activities children develop essential social skills, including how to compromise, work as a team, and deal with conflicts and different personality styles.

Poor motor coordination often results in significant social and emotional consequences. When a child is poorly coordinated, she or he is often teased and shunned from group play. This may lead to anxiety and avoidance of participation in games, as children frequently judge themselves to be both physically and socially less competent. Anxiety may be more prevalent in adolescence, most notably in boys. Because they are often unsuccessful in group participation, difficulties with navigating the changing demands of cooperative play and negotiating with others and reluctance to advocate for themselves often result. Boys with learning and motor coordination problems have been found to demonstrate significantly less effective coping strategies in all domains of functioning compared with a normative sample. Feelings of incompetence, depression, or frustration are common and can be lifelong problems. ^, The impact of motor coordination difficulties on social behavior is exemplified by this statement from a child with learning disabilities and motor deficits:

Gross motor characteristics of DCD include the following:

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  Diminished core strength and postural control

  
  
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  Delayed balance reactions

  
  
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  Often falling, tripping, and bumping into things; acquiring more than the usual number of bruises

  
  
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  Motor movements that are performed at a slower rate despite practice and repetition

  
  
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  Motor milestones that may be achieved in the later range of normal development

  
  
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  Poor anticipation (do not use knowledge of past performance to prepare)

  
  
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  Notably different quality of running and ball skills from typical peers

  
  
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  Difficulty learning bilateral tasks such as riding a bicycle, catching a ball, and jumping rope

  
  
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  Possible hesitance with and avoidance of new or complex motor tasks (e.g., playground equipment, gym class)

  
  
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  Possibly poor safety awareness

  
  
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  Inability to smoothly turn and position body when going up ladder to a slide or to get into a chair

  
  
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  Possible sedentary activity level; may prefer to engage in solitary play

  
  
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  Tendency to not play games by the rules

  
  
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  Often, avoidance of team sports such as T-ball and soccer

Fine motor characteristics of DCD include the following:

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  Diminished wrist and hand strength

  
  
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  Maladaptive or immature grasp patterns

  
  
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  Possible use of excess or not enough pressure

  
  
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  Poor refinement of small motor movements with hands (qualitatively, the child looks like he or she is wearing a pair of gloves when trying to manipulate small objects)

  
  
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  Often dropping or breaking items

  
  
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  Delayed dressing skills (buttons, zippers, fasteners, shoelaces)

  
  
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  Trouble with eating utensils (scooping, piercing)

  
  
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  Difficulty with tool use (e.g., scissors, pencils, stapler, hole punches)

  
  
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  Writing that is laborious and often illegible

  
  
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  Impaired drawing ability characterized by poor motor control, with wobbly lines, inaccurate junctures, and difficulty coloring within the lines

  
  
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  Decreased ability with pasting, gluing, manipulating stickers and other art materials

  
  
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  Difficulty with constructive, manipulative play (e.g., block building, Tinkertoys, Legos)

  
  
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  Often the presence of associated articulation deficits, possibly because of the fine motor nature demanded for articulation

Visual motor characteristics of DCD include the following:

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  Difficulty with visually guided motor actions (i.e., eye-hand and eye-foot coordination)

  
  
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  Hesitancy or decreased safety on stairs

  
  
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  Trouble with timing needed for kicking, hitting, and catching ball

  
  
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  Difficulty with hopscotch and four squares

  
  
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  Poor judgment of spatial relationships (knowing where the body is in space)

  
  
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  Delayed development of prepositional and directional concepts

  
  
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  Difficulty with spatial planning tasks such as puzzles, building models, and constructional toys

  
  
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  Handwriting that is often labored, with spacing and sizing problems evident; letters may be irregular, illegible, and poorly organized on the page

Self-care characteristics of DCD include the following:

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  Slowness to develop independence in ADLs

  
  
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  Overreliance on parents to help with self-care skills

  
  
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  Clothes that are often on backward or crooked

  
  
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  Struggles with cutting fingernails, putting on makeup, tying necktie, using a hair dryer

  
  
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  Difficulty blowing nose with tissue, putting on Band-Aid

  
  
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  Trouble putting toothpaste on toothbrush

  
  
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  Messy eater, spills often, does not recognize food on face

  
  
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  Difficulty pouring from a container, opening lunch box, unwrapping sandwich, opening containers, peeling fruit

  
  
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  Trouble packing a bag, backpack, or suitcase

  
  
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  Difficulty sequencing daily routines

Social and emotional characteristics of DCD include the following:

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  Often emotionally immature

  
  
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  May exhibit behavioral difficulties such as acting out or becoming class clown

  
  
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  May be more introverted and anxious

  
  
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  Can appear fiercely competitive, hating to lose, complaining that rules are unfair

  
  
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  Can be self-deprecating, calls self “stupid”

  
  
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  Often easily frustrated

  
  
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  May experience depression and feelings of incompetence

  
  
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  Has difficulty making and maintaining friendships, plays alone

  
  
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  Has feelings of low self-worth, poor self-esteem

  
  
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  Perceived by others as lazy, overprotected, or immature

  
  
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  Adolescents may have fewer social pastimes and hobbies than peers

Prevalence

The prevalence fluctuates between 4% and 5% in mainstream primary schools ^, to 6% of the population, and more recently, up to 10% worldwide. Prevalence is directly related to the way the assessment is used and the establishment of cut-off points. Gender differences have been examined on numerous occasions, and the consensus is that the condition is more prevalent in boys than girls, with a ratio of 2.

Perspectives on the causes of developmental coordination disorder

There is no single explanation for the cause of DCD. Neurological dysfunction, physiological factors, genetic predisposition, and prenatal and perinatal birth factors have been proposed to explain the basis of DCD. ^, It is recognized that DCD is heritable and is genetically distinct from attention-deficit/hyperactivity disorder (ADHD), although the comorbidity rate is up to 50%. Comorbidity is high with other diagnoses, including autism spectrum disorders, as well as a variety of developmental learning problems such as math disability, reading disability, specific language disabilities, spelling and writing disabilities, and so on. Correlation has also been noted between preterm infancy and low birth weight with characteristics of DCD. The heterogeneity of DCD makes finding a unitary cause difficult. Children with DCD present wide variability in both locus of specific problems and functional disabilities. Further complicating an understanding of the cause is that the intervention for the child with DCD is driven by competing treatments.

Few studies have been conducted to look at brain images in children with DCD, with no particular patterns of abnormality observed. Hadders-Algra has suggested that DCD is a result of damage at the cellular level in the neurotransmitter and receptor systems, rather than a specific region of the brain. Resulting coordination difficulties can be from a combination of one or more impairments in proprioception, motor programming, timing, or sequencing of muscle activity.

Possible physiological origins of motor coordination deficits have highlighted multisensory processing. Ayres, in her theory of sensory integration, suggested that the integration among sensory systems is imperative for refined motor performance in children. She proposed that normal development depends on intrasensory integration, particularly from the somatosensory and vestibular systems. Lane outlines the role of vision, combined with vestibular and proprioceptive inputs, as a foundation to motor performance. In combination, these systems sustain postural tone and equilibrium, provide awareness and coordination of head movements, and stabilize the eyes during movement in space.

More recently, Piek and Dyck found support for the correlations between DCD and deficits in kinesthetic perception, visual-spatial processing, and multisensory integration. In general, it is thought that reduced rates of processing information and deficits in handling spatial information may underlie the deficits in motor control. Obviously more work is needed on the cause of DCD.

Subtypes of developmental coordination disorder

Various approaches have been used to investigate subtypes of DCD, including classification by underlying causes, clinical and descriptive approaches, and statistical clustering. Initial attempts at classifying subtypes within DCD support the heterogeneity of this group of children. Work by Dewey and Kaplan suggests that children with DCD may be classified into subgroups based on distinctions in motor planning and motor execution deficits. They identified three subgroups: children who exhibited deficits in motor execution alone, those whose primary deficits were in motor planning, and children who exhibited a generalized impairment in both areas.

Macnab and colleagues identified five different profiles of children with DCD. They used measures of kinesthetic acuity, gross motor skill, static balance, visual perception, and visual motor integration. Two distinct groups emerged, with children exhibiting generalized visual deficits and generalized dysfunction in all areas. Generalized gross motor deficits did not emerge as a distinct subgroup, because the third group demonstrated a discrepancy between static balance and complex gross motor tasks, and the fourth group had poor performance on running but performed well on kinesthetic acuity. Other groups included children with deficits in visual motor and fine motor problems. These results suggest that a subtype based on motor execution or planning problems alone may be too general.

Diagnosis

A two-step approach to assessment using the Movement Assessment Battery for Children (M-ABC) is the preferred standardized measure for motor impairment. The M-ABC checklist is used as a guide to examine the effects on daily living. The M-ABC is the most widely used instrument and contains a standardized normative referenced test, plus a criterion-referenced test. The diagnosis of DCD is made for those scoring at or below the fifth percentile checklist. The M-ABC consists of three subtests: manual dexterity, ball skills, and static and dynamic balance. Each subtest is given a score and totaled for an overall impairment score. A higher numerical score is indicative of a higher level of impairment.

DCD may co-occur with other disorders such as ADHD, dyslexia, and autism spectrum disorders. There is also evidence suggesting that one-third of children with speech and language impairment are likely to have DCD as well. Because of the heterogeneous nature of the disorder, it is often underrecognized by health care professionals. In a survey of the physicians from Canada, the United States, and the United Kingdom, only 41% of pediatricians and 23% of general practitioners had knowledge of the condition. Furthermore, only 23% of the pediatricians and 9% of the general practitioners surveyed had ever diagnosed DCD. A systematic review involving school-aged children showed significantly greater odds of developing DCD among children who had very low birth weights (<1500 g) or were very preterm (<32 weeks) than among age-matched controls born at term with normal birth weights.

Neurophysiology

There is no clear etiology for DCD; however, it is a recognized as a central processing disorder. , Some early studies have considered the neural mechanisms potentially implicated in DCD. However, the underlying neural processes remain unclear and the heterogeneous nature of the disorder further confounds attempts to find an underlying cause. The cerebellum is believed to be more implicated than peripheral mechanisms in the pathophysiological mechanisms of DCD. The behavioral manifestations of lack of postural control and lack of coordination suggest involvement of cerebellum, basal ganglia, and frontal and parietal lobes. The cerebellum might also be involved in the pathophysiology of DCD, because a disruption of the cerebellocerebral network has been given as an explanation for DCD. In skilled action, cerebellar and parietal areas process information and their outputs are integrated into one smooth movement. The posterior parietal cortex appears to also be involved with a faulty “feedforward mechanism” where the person cannot create an efference copy of a motor plan and thus has an “efference copy deficit.” The use of visual information sources in the guidance of goal-directed behavior was studied by de Oliveira and Wann through visual pursuits. The DCD subjects showed an impaired internal model with inadequate forward or predictive model of movement and difficulties in skilled movement when near and far visual information were present; therefore it is possible that integration of cerebellar and parietal areas was inadequate.

Assessment of motor impairments

A variety of professionals may be involved in a comprehensive assessment of motor deficits. Pediatric OTs and PTs are often the core team assessing functional motor concerns. Areas assessed by pediatric OTs and PTs often overlap, so communication is essential to ensure that testing is not replicated. Ideally, performance will be evaluated in multiple environments and include components of skill, functional performance areas, and social and societal participation. Specific recommendations should include activities to enhance performance in the environments in which the child functions.

Clinical judgment of the therapist is important in designing an assessment protocol and synthesizing information to create a complete profile of the child. A variety of standardized and nonstandardized evaluation tools should accompany structured clinical observations and caretaker interviews. Observations of the child can yield more readily usable information than a standardized score, enabling the therapist to view the child in natural routines, self-directed activities, and unstructured play. The interview process is essential to gather information about the child’s interactions and participation. This process paints a verbal picture of the child to help us to understand levels of functioning and participation in a variety of environments. Other crucial information obtained is how the child’s difficulties are affecting the ability to parent or teach the student.

Before choosing an evaluation tool the therapist should be aware of the intended purpose of this measure. Tools used to assess children with DCD are used for distinct purposes: identify impairments, describe severity of impairments, or explore activity or participation limitations. The choice of evaluations may also be determined by the setting, frame of reference of the therapist, and functional concerns of the child. A therapist should be familiar with all aspects of test administration and scoring for evaluation tools and should comply with the training requirements described in the test manual. Test construction, reliability, and validity for assessing DCD should be considered. Appendix 12.A provides an overview of standardized tests available for the assessment of motor dysfunction in children with learning disabilities. Uses and limitations of the individual tests and test batteries are listed.

Identification of subtle motor difficulties is critical and challenging. These subtle motor difficulties initially can be undetected, leading to unrealistic expectations of age-level motor performance. The child’s difficulty with skilled, purposeful manipulative tasks or with finely tuned balance activities may not be readily apparent in the classroom or may be perceived as lack of effort. Children with DCD may be able to perform certain motor tasks with a level of strength, flexibility, and coordination that is qualitatively average but must use increased effort and cognitive control for sustained success.

Levels of performance in gross and fine motor testing may fall in the borderline range. Careful observations are of paramount importance because the child’s deficits are often qualitative rather than quantitative. A child might have age-appropriate balance on testing but lack ability in weight shifting and making quick directional changes, which affects the ability to participate in extracurricular activities such as soccer or baseball. When assessing children with subtle motor deficits, it is important to realize that many evaluation tools have been developed for children with moderate to severe neurological impairments.

Children with DCD do not exhibit obvious evidence of neuropathological disease (i.e., “hard” neurological signs such as a cerebral lesion). Subtle abnormalities of the central nervous system are frequently noted by the presence of “soft” neurological signs. Deficits associated with soft neurological signs include abnormal movements and reflexes, sensory deficits, and coordination difficulties. Evaluation of soft neurological signs is typically part of an examination by a pediatric neurologist, although therapists can assess these areas in conjunction with standardized testing. Box 12.2 lists soft neurological signs frequently used to assess this population.

BOX 12.2

Common Soft Neurological Signs Used in Assessment of Children With Learning Disabilities and Motor Deficits

Minor neurological indicators

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  Left-right discrimination

  
  
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  Finger agnosia

  
  
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  Visual tracking

  
  
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  Extinction of simultaneous stimuli

  
  
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  Choreiform movement

  
  
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  Tremor

  
  
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  Exaggerated associated movements

  
  
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  Reflex asymmetries

Coordination

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  Finger-to-nose touching

  
  
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  Sequential thumb-finger touching

  
  
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  Diadochokinesia

  
  
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  Heel to shin

  
  
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  Slow controlled motions

  
  
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  Postural-motor measures

  
  
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  Muscle tone

  
  
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  Schilder’s arm extension posture

  
  
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  Standing with eyes closed (Romberg test)

  
  
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  Walking a line

  
  
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  Tandem walking (forward and backward)

  
  
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  Hopping, jumping, skipping

  
  
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  Ball throw and catch

  
  
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  Imitation of tongue movements

  
  
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  Pencil and paper tasks

  
  
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  Fine motor tasks (stringing beads, building block towers)

Sensory indicators

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  Graphesthesia

  
  
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  Stereognosis

  
  
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  Localization of touch input

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