CHAPTER 11

Developmental and behavioral disorders are the most prevalent chronic medical diagnoses encountered by primary pediatric health care professionals.1 Given their frequent, longitudinal contact with children and their families, primary pediatric health care professionals are ideally positioned to identify children with possible developmental delays and behavioral problems within the medical home through the processes of developmental surveillance and screening (see Chapter 9, Developmental and Behavioral Surveillance and Screening). Once a failed screen provides a chief complaint of a developmental or behavioral concern, a medical approach to making developmental-behavioral diagnoses begins with obtaining comprehensive medical, social, family, and developmental histories, performing physical and neurological examinations, and completing direct developmental evaluations² (see Chapter 10, Developmental Evaluation). Once this process has been completed, primary pediatric health care professionals need to make specific developmental-behavioral diagnoses, such as intellectual disability (ID), autism spectrum disorder (ASD), cerebral palsy (CP), learning disabilities (LD), attention-deficit/hyperactivity disorder (ADHD), and developmental coordination disorder (DCD), and to attempt to determine a specific medical etiology to account for the developmental-behavioral diagnoses made. However, to fully understand any single specific diagnosis, given overlap in symptomatology and frequent comorbidities, one first needs to appreciate the entire spectrum and continuum of developmental-behavioral diagnoses.

Developmental Versus Etiological Diagnosis

The process of making comprehensive developmental-behavioral diagnoses is twofold— each child requires a descriptive developmental-behavioral diagnosis (eg, CP, ID, LD, ADHD, ASD), but it is also imperative to pursue an appropriate laboratory workup (eg, chromosome microarray analysis, DNA testing for fragile X syndrome, metabolic studies, head imaging, whole-exome sequencing) in an attempt to establish an etiological diagnosis to account for each child’s descriptive developmental-behavioral diagnoses (see Chapter 4, Biological Influences on Child Development and Behavior and Medical Evaluation of Children With Developmental-Behavioral Disorders). For example, a child who exhibits a static pattern of severe global developmental delays may receive a descriptive developmental diagnosis of ID; however, laboratory workup may reveal the child to have a chromosomal deletion syndrome. The specific chromosomal deletion is the etiology to account for the child’s ID. Similarly, a child described as evidencing the developmental-behavioral patterns that meet criteria for a descriptive developmental diagnosis of CP may be found at brain magnetic resonance imaging (MRI) to have periventricular leukomalacia. The hypoxic-ischemic event that produced the periventricular leukomalacia is the etiology of the child’s CP.

The distinction between descriptive and etiological diagnoses for children with developmental-behavioral disorders is illustrated in Figure 11.1. Etiological diagnoses for all neurodevelopmental/neurobehavioral disorders result from an interaction between neurobiological factors (genetic/epigenetic, metabolic, toxic, infectious, etc) and environmental experiences (developmental stimulation received in home or child care environments, exposure to toxic stress, etc.; see Chapter 2, Nature, Nurture and Interactions in Child on Development and Behavior; Chapter 3, Environmental Influences on Child Development and Behavior; and Chapter 4, Biological Influences on Child Development and Behavior and Medical Evaluation of Children With Developmental-Behavioral Disorders). This interaction can result in what has been described as “developmental brain dysfunction,”^3,4 which produces a pattern of neurocognitive, neurobehavioral, and/or neuromotor impairments represented by Capute’s triangle (which will be described herein).^5,6 Once this pattern of impairments has been established, descriptive developmental- behavioral diagnoses (eg, ID, ASD, CP, LD, ADHD) can be made along the spectrum and continuum of developmental-behavioral disorders.

The descriptive nature of developmental-behavioral diagnoses is illustrated by the fact that the same developmental-behavioral diagnosis can be caused by multiple different genetic etiologies (eg, ID is caused by multiple different genetic etiologies), and the same genetic etiology can cause multiple different developmental-behavioral diagnoses (eg, ID, autism, or schizophrenia can all be caused by the same copy number variant).^7,8 Further, descriptive developmental-behavioral diagnoses may change over time in the same individual. For example, Nelson and Ellenberg reported that just over half of children who were diagnosed with CP at 1 year of age no longer had this diagnosis at 7 years of age.⁹ However, despite this loss of one descriptive developmental-behavioral diagnosis, children who “outgrew” CP were more likely at age 7 years to have other neurodevelopmental diagnoses, such as ID, speech articulation disorders, and seizures.⁹ Similarly, Helt et al reported that up to 25% of children diagnosed to have ASD will lose that descriptive developmental-behavioral diagnosis over time.¹⁰ However, children who “outgrow” autism appear to be at higher risk for residual vulnerabilities affecting higher-order communication and attention, tics, depression, and phobias.¹⁰ Finally, Barbaresi et al reported that among children diagnosed with ADHD, only about 30% continued to have a descriptive developmental-behavioral diagnosis of ADHD as adults.¹¹ However, adults who “outgrew” the diagnosis of ADHD were at increased risk of multiple neurobehavioral disorders, including substance use disorders, antisocial personality disorder, anxiety, hypomania, and depression.¹¹ In each of these cases, the descriptive developmental-behavioral diagnoses changed over time in the same individuals, but the “developmental brain dysfunction” caused by the interaction of each individual’s neurobiology and environmental experiences remains the etiological diagnosis for the range of descriptive developmental-behavioral diagnoses encountered over time.

Age at Diagnosis Depends on the Severity of a Developmental-Behavioral Disorder

Although it is critical to make developmental-behavioral diagnoses at as early an age as possible, and the American Academy of Pediatrics (AAP) has recommended the use of standardized developmental screening instruments at specified ages to identify delays early,12 it is important to note that mild disabilities are much more common than severe disabilities. Further, the more subtle the developmental-behavioral disorder, the older a child must be before his or her development or behavior is appreciably different from similarly aged peers, such that the developmental or behavioral disorder can be reliably identified.¹³ Alternatively, the more severe the disability, the younger the age at which it can be reliably identified. For example, a child with severe ID is likely indistinguishable from a child with average intelligence on a newborn neurodevelopmental assessment, but severe ID should be suspected by one year of age—at one year of age, children with severe ID would be expected to show developmental skills at the level of a 6-month old or below, which should be clearly distinguishable at 1 year of age. However, of all children with ID, approximately 85% will have mild ID¹⁴; many of these children may not be reliably identified until they reach at least 3 years of age, when their developmental skills would be expected to be at an approximate 2-year-old level or below, clearly behind their similarly aged peers. Thus, some children with mild ID may well not be identified by developmental screens performed in the first 3 years of life, when such screens are recommended at specified ages. In fact, it appears likely that many individuals with mild ID are actually never identified. While statistically, based on a normal distribution of intelligence, the prevalence of ID should be between 2% and 3%, prevalence rates determined by ascertainment are closer to 1% due to methodological problems in identifying individuals with mild ID—it appears that as adults, many individuals with mild ID blend in with and become indistinguishable from other members of the community.¹⁴ Further, the most subtle of cognitive disabilities, the specific learning disabilities (LD), such as dyslexia, certainly cannot be diagnosed in the first 3 years of life and are typically not diagnosed until a child begins to have difficulty keeping up with peers at school. Similarly, while intensive early intervention strategies have been shown to benefit children with ASD,¹⁵ not all children with ASD can be identified by screening in the birth-to-3-year population.¹⁶ The behavior of children with milder cases of high-functioning ASD might not be recognized to be significantly different from that of peers until older ages, when there are increasingly complex demands for peer social interaction and communication. Thus, while early recognition and intervention should always be the primary goal, it remains difficult to identify the much more common milder disabilities in the birth-to-3-year age range with the use of standardized developmental screening techniques.

Primary Developmental-Behavioral Diagnosis and Associated Deficits (Comorbidities)

As opposed to adult neurology, where acquired focal neurological deficits derivative of etiologies such as cerebrovascular accidents are common, the neuropathology in developmental-behavioral disorders of childhood tends to be more diffuse. While each child with a developmental-behavioral disorder will typically receive a primary developmental-behavioral diagnosis (eg, CP, ID, LD, ASD, or ADHD), associated deficits or comorbidities are the rule, rather than the exception, in children with these disorders. For example, approximately 13% of children with ID also have CP,17 and 30% of children with ID have ADHD.¹⁸ Approximately 50% of children with CP also have ID.¹⁷ Further, about 40% of children with ASD also have ID.¹⁹ In addition, about 60% of children with ADHD have LD,²⁰ and 50% have motor coordination disorders.²¹

Such diffuse neurological dysfunction should not be unexpected given the etiological entities that typically cause developmental-behavioral disorders. For example, a child with a chromosomal abnormality, such as a trisomy or chromosome deletion, would evidence the chromosomal abnormality in every neuron of the brain. Thus, diffuse neurodevelopmental dysfunction should be expected to result from such diffuse brain involvement. Similarly, other hypoxic-ischemic, metabolic, infectious, or toxic causes of brain dysfunction or the effects of environmental neglect or understimulation on a developing brain would also be expected to cause more diffuse rather than focal neurodevelopmental impairments. Therefore, while in this chapter a spectrum of developmental-behavioral disorders from mild to severe will be described within each of 3 primary streams of development (motor, cognitive, and neurobehavioral streams), one must remember that there is also a continuum of developmental-behavioral disorders across developmental streams: Children with primary motor disorders are likely to have associated cognitive, learning, or behavioral difficulties; children with primary cognitive disorders are likely to have associated neurobehavioral and motor issues; and children with primary neurobehavioral disorders are likely to have associated learning, cognitive, and/or motor impairments.

Delay, Dissociation, and Deviation

Developmental-behavioral disorders occur along a spectrum and continuum from high-prevalence, lower-morbidity conditions (eg, DCD, LD, and ADHD) to low-prevalence, higher-morbidity conditions (eg, CP, ID, and ASD). Capute and Accardo have described a model for enhancing developmental-behavioral diagnosis through understanding this spectrum and continuum via analysis of 3 fundamental neurodevelopmental processes: delay, dissociation, and deviation.^22,23 Developmental delay refers to a significant lag in the attainment of developmental milestones; as reviewed previously, given that the etiological entities that result in developmental-behavioral disorders tend to produce diffuse neurological dysfunction, developmental delay is most commonly represented by a more global delay across all streams (cognitive, neurobehavioral, motor) of development.

Developmental dissociation describes a significant difference between the developmental rates of two streams of development, with one stream significantly more delayed. Developmental dissociation thus describes significant scatter or unevenness across different streams of development. Given that developmental delays are typically more global in nature, dissociations between developmental streams are less commonly encountered and should be recognized as atypical, even in a setting where dissociation exists without corresponding significant developmental delay. For example, specific LD represents an example of developmental dissociation. Specific LD has traditionally been defined by a significant discrepancy, or dissociation, between intelligence and academic achievement. Learning disabilities may also be defined by a significant dissociation between verbal and nonverbal cognitive abilities. In language-based LD (LLD), a significant dissociation exists between relatively stronger nonverbal and relatively weaker verbal cognitive abilities, while in nonverbal LD (NVLD), there exists a significant dissociation between relatively weaker nonverbal versus relatively stronger verbal cognitive abilities. Similarly, ADHD can be defined as a dissociation between neurobehavioral and cognitive streams of development, as children with ADHD have levels of inattention, poor impulse control, and excessive motor activity that are discrepant from their levels of cognitive development (ie, these behaviors are developmentally inappropriate compared to their cognitive abilities).

Developmental deviation represents nonsequential unevenness in the achievement of developmental milestones (ie, achieving higher-age-level developmental milestones in a typical developmental sequence prior to achieving lower-age-level developmental milestones); such deviated acquisition of developmental milestones is considered to be atypical at any age.22 While developmental dissociation refers to significant scatter or unevenness of developmental abilities across different developmental streams, developmental deviation is defined by significant scatter or unevenness of abilities within a single developmental stream. Developmental deviation in motor development is most often observed in children with CP. For example, a child with CP may be observed to exhibit higher-level motor milestones, like being able to stand next to a table (which is expected at around 8 months of age), before exhibiting lower-level developmental milestones, such as rolling over (expected at around 4 to 5 months) or sitting independently (expected at 6 to 7 months), with the ability to stand being secondary to lower extremity spasticity or to a persistent positive support primitive reflex. Children with ASD most often exhibit developmental deviation in cognitive and neurobehavioral development. For example, deviation in the language component of cognitive development may be observed in a child with ASD who has a 50-word vocabulary (expected at 24 months) prior to using a specific “mama” and “dada” to refer to his or her parents (expected at 10 months). Many children with ASD persist in using echolalia and confusing pronouns (atypical after 30 months) despite having higher-age-level, single-word vocabularies. Deviation in social and neurobehavioral development observed in children with ASD can be defined as behavior that is atypical at any age. Thus, deviation in social development is exemplified by the impairment in reciprocal social interaction and lack of interest in peers observed in ASD, while an example of deviation in neurobehavioral development is the atypical attention observed in children with ASD, who exhibit fleeting attention to maintaining eye contact, but who are overly focused or perseverative on restricted areas of interest.

While every individual exhibits a unique pattern of developmental strengths and weaknesses, the terms dissociation and deviation are applied to describe more significant scatter or unevenness of developmental abilities, both across (dissociation) and within (deviation) developmental streams, than is typically encountered. This model postulates that developmental delay, dissociation, and deviation reflect underlying central nervous system (CNS) dysfunction. Consequently, the amount of delay, dissociation, and/or deviation encountered increases as one moves from the mild to severe end of the spectrum and continuum of developmental-behavioral disorders. Increasing levels of developmental delay, dissociation, and deviation reflect increasingly atypical development, and increasingly atypical development is usually accompanied by increasingly atypical behavior. As will be discussed herein, this model predicts that the most atypical pattern of neurobehavioral development, as observed in children with ASD, is most commonly accompanied by the most delayed, dissociated, and deviated patterns of cognitive development.

The AAP annually presents the Dr Arnold J. Capute Award to recognize a physician who has made notable contributions to the health and well-being of children with developmental disabilities through service and/or advocacy. Dr Capute described a model for making developmental-behavioral diagnoses that distills the highly complex functions of the brain into a triangle of 3 primary streams of development: motor, cognitive, and neurobehavioral (see Figure 11.2).^5,6 The motor stream of development includes gross motor, fine motor, and oral motor development. The cognitive stream of development includes the language and visual-motor problem solving developmental streams, which come together to form the social (which is primarily communicative [eg, social smile, gestured language, pragmatic language]) and adaptive (which primarily depends on visual-motor abilities [spoon feeding, tying of shoes, etc]) streams.²² The neurobehavioral stream of development could be considered to contain all of neuropsychiatry, but this chapter will focus on the neurobehavioral streams of attention and activity level.

Figure 11.2. Capute’s triangle. Adapted from Capute AJ. The expanded Strauss syndrome: MBD revisited. In: Accardo PJ, Blondis TA, Whitman BY, editors. Attention Deficit Disorders and Hyperactivity. 1991; New York: Marcel Dekker, Inc. p 28.

Developmental-behavioral disorders exist across a spectrum of severity, from mild to severe, within each of the 3 primary developmental streams, with mild disabilities predominating over severe disabilities. There is also a continuum of developmental-behavioral disorders across these 3 developmental streams, as primary developmental-behavioral diagnoses in one stream are usually accompanied by associated deficits or comorbidities in one or both of the other developmental streams.

After a child has failed a developmental screen, the primary pediatric health care professional will then ascertain the child’s degree of developmental delay, dissociation, and deviation within and across the motor, cognitive, and neurobehavioral streams of development via a comprehensive developmental history and direct developmental evaluation (see Chapter 10, Developmental Evaluation). An analysis of the degree of developmental delay, dissociation, and deviation that a child evidences within and across the motor, cognitive, and neurobehavioral streams of development directs the clinician in choosing the most appropriate developmental-behavioral diagnoses to apply along the spectrum and continuum of developmental-behavioral disorders.

The following will describe a framework for conceptualizing the relationship among the various developmental-behavioral diagnoses. It is hoped that this model will provide a structure for primary pediatric health care professionals to more confidently make developmental-behavioral diagnoses within the medical home. Of course, this model should not substitute for using currently accepted diagnostic criteria when a specific developmental-behavioral disorder (eg, ASD, ADHD, LD) is suspected. Chapters to follow will specifically review current diagnostic criteria for each developmental-behavioral diagnosis; this model serves to introduce the relationship among these overlapping descriptive entities.

The Spectrum of Global Developmental Delay

The cognitive stream of development is composed of 4 primary domains of central processing: language, social, adaptive, and visual-motor problem solving. In the spectrum of global developmental delay, delays in verbal, nonverbal, social, and adaptive development are generally equivalent (without any significant dissociation or deviation) and increase in severity as one moves from the mild to severe end of the spectrum of global developmental delay. This spectrum provides the most distinct diagnostic entities, as diagnoses in this spectrum are defined by specific IQ and adaptive behavior scores in a normal distribution (see Figure 11.3).

Figure 11.3. Spectrum of global developmental delay.

At the mild end of this spectrum, the Wechsler Intelligence Scale for Children—Revised previously classified IQ scores between 80 and 89 as the “dull” range of intelligence.²⁴ Currently, while children who function in this range of intelligence are classified as “low average” by the Wechsler Intelligence Scale for Children, Fifth Edition,²⁵ they might more descriptively be referred to as “slower learners,” as they typically experience significant difficulties keeping up in regular classroom settings.²⁶ As the global developmental delay becomes more severe across this spectrum, children with IQ scores between 70 and 79 are described as evidencing borderline intelligence, and those with IQ and adaptive behavior standard scores below 70 are defined as having ID (see Chapter 15, Cognitive Development and Disorders). As with disorders across all developmental streams, mild global developmental delays predominate over severe global developmental delays, as 23% of the population evidences slower learning or borderline intelligence, while statistically only between 2% and 3% of the population would be expected to evidence ID (although only 1% of the population is actually identified as evidencing ID due to methodological problems in identifying individuals with mild ID).¹⁴

Global developmental delay is the most typical developmental-behavioral presentation, while developmental dissociation and deviation are less common and more atypical developmental presentations. However, within each of the primary streams of development—motor, cognitive, and neurobehavioral—there exists a spectrum of dissociated and deviated developmental-behavioral diagnoses, which will be reviewed herein.

The Spectrum of Motor Dissociation and Deviation

The motor stream of development includes the development of gross motor, fine motor, and oral motor (speech, chewing/swallowing) skills. There is a spectrum of motor disorders within each of these motor areas, with mild motor disorders occurring more frequently than more severe disorders (see Figure 11.4). As one moves across the spectrum of dissociated motor disorders from mild to severe, increasing deviation occurs, as motor deviation is commonly observed in children with CP.

Figure 11.4. Spectrum of motor dissociation and deviation. Abbreviation: DCD, developmental coordination disorder.

The mild end of the spectrum of motor dissociation and deviation has in the past been described as the “clumsy child syndrome” or “developmental dyspraxia,”²⁷ but it is described in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), as “developmental coordination disorder” or DCD.²⁸ At this mild end of the motor spectrum, children evidence mild gross motor delays and difficulties with motor planning, and many evidence “soft” neurological signs (eg, synkinesias, choreiform movements, dysdiadochokinesis, and posturing of the upper extremities with stressed gaits).29 As motor delay increases in severity within this spectrum, and is accompanied by “hard” neurological signs (persistent primitive reflexes, brisk deep tendon reflexes, spasticity, dyskinesia, ataxia, hypotonia), a diagnosis of CP becomes more appropriate. Minor fine motor deficits produce difficulties with handwriting (dysgraphia) and delays in accomplishing activities of daily living, such as buttoning and tying shoes, while more severe fine motor delays are also seen in quadriparetic and hemiparetic forms of CP. From an oral motor standpoint, the mild end of this spectrum includes mild speech articulation difficulties and milder feeding issues, while the severe end includes the dysphagia and dysarthria that frequently accompany more severe forms of CP. Consistent with disorders within all streams of development, mild motor disorders predominate over severe motor disorders. There are many more children with gross motor clumsiness, handwriting difficulties, and speech articulation disorders (with an estimated prevalence of DCD of 10%)²⁷ than there are with CP (which has a prevalence of 2.9 per 1,000 or only 0.29%)³⁰ (see Chapter 14, Motor Development and Disorders).

The Spectrum of Cognitive Dissociation and Deviation

The cognitive stream of development consists of the language and visual-motor problem-solving streams that come together to form the primarily communicative social and primarily visual-motor–dependent adaptive streams.²² Within the spectrum of global developmental delay described previously, there is no significant discrepancy or dissociation among these cognitive streams of development. However, such discrepancies between cognitive streams and deviations within these cognitive streams can and do occur, and they exist across a spectrum from mild to severe.

The Spectrum of Language Dissociation and Deviation

When children evidence discrepant and disproportionate delays in their language development relative to their nonverbal visual-motor problem-solving development, their developmental diagnoses will lie within the spectrum of language dissociation and deviation (see top portion of Figure 11.5). Of course, when a child presents with discrepant delays in speech or language development, primary pediatric health care professionals first need to formally confirm the child’s hearing status prior to making a diagnosis within this spectrum. As one moves from the mild to severe end of this spectrum, in addition to evidencing dissociated delays in more diffuse aspects of language relative to nonverbal problem solving, increasing amounts of developmental deviation in language milestone acquisition and social communication are observed.

Language consists of 5 components: phonology, morphology, syntax, semantics, and pragmatics, with phonology, morphology, and syntax comprising the “form of language,” semantics comprising the “content of language,” and pragmatics comprising the “use of language” (see Chapter 16, Speech and Language Development and Disorders). The mild end of the spectrum of language dissociation and deviation thus involves a dissociation in only one of these domains: phonology. Such a relatively focal deficit in phonological processing is the primary neuropsychological deficit observed in children with dyslexia,³¹ and children with phonological processing deficits can be described as having dysphonetic dyslexia (see Figure 11.5). Children with phonological processing deficits have difficulty rhyming words and associating sounds with written symbols. They have difficulty with reading decoding (given their difficulty in sounding out words that they do not know), although they may be able to visually memorize lists of sight words (given their preserved nonverbal orthographic processing abilities). They can also understand material that is read to them, given that the components of language development other than phonology (morphology, syntax, semantics, and pragmatics) are preserved. Most children with reading disabilities evidence underlying difficulties with phonological processing, and they have traditionally been identified by schools based on a dissociation between their IQ scores and their discrepantly low achievement scores in reading. When comparing the cognitive component at the mild end of the spectrum of global developmental delay (slower learning) with the mild end of the spectrum of language dissociation and deviation (dysphonetic dyslexia), it is again confirmed that more diffuse or global cognitive dysfunction predominates over more focal or dissociated cognitive dysfunction, as more global slower learning affects 23% of the population, while discrepancy-based reading disabilities affect only 8%.³²

As more diffuse components of receptive and expressive language become discrepantly delayed (or dissociated) compared to nonverbal visual-motor problem-solving, an individual can be described as evidencing a language disorder, which can also be described as developmental dysphasia or a specific language impairment. As more diffuse aspects of the form and content of receptive and expressive language (phonology, morphology, syntax, and/or semantics) become discrepantly delayed, verbal reasoning is negatively impacted, and a point is reached where verbal reasoning is found to be significantly below nonverbal reasoning on IQ testing. Such a significant discrepancy or dissociation between verbal and nonverbal IQ is often classified as LLD. Rather than evidencing a relatively isolated difficulty in reading decoding as seen in dyslexia, individuals with LLD evidence more diffuse academic difficulties in listening comprehension, oral expression, reading comprehension, written expression, and math word problems.

As one moves toward the most severe end of the spectrum of language dissociation and deviation, dissociated delays in the pragmatic component of language occur, and pragmatic language use or social communication is discrepantly delayed (dissociated) compared to the level of language form (morphology/word structure and syntax/grammar). These discrepant delays in pragmatic language include both verbal (difficulties with greeting, requesting, commenting, etc) and nonverbal (difficulties with eye contact, understanding and using facial expressions and gestures, etc) aspects of social communication. As one moves toward the severe end of this spectrum, increasing developmental deviation also tends to occur. This includes deviated acquisition of language milestones (eg, having a 50-word vocabulary but not yet using gestured language or a specific “Mama” or “Dada”; persistent use of echolalia or pronoun confusion despite upward deviation in more rote aspects of language [such as rote auditory memory, including memorizing song lyrics or having a large vocabulary based on the memorization of labels]) and deviated or atypical social interaction (eg, impairments in reciprocal social interaction, lack of interest in peers). Thus, individuals at the severe end of this spectrum have both language disorders and impairments in the pragmatic/social use of language that are described as social communication disorders. Both language disorders and social communication disorders have specific diagnostic criteria in the DSM-528 (see Chapter 16, Speech and Language Development and Disorders, and Chapter 19, Autism Spectrum Disorder).

The language and social communication deficits observed at the severe end of the spectrum of language dissociation and deviation represent the most developmentally dissociated and deviated end of the language and social domains of cognitive development, and thus represent the most atypical presentation of language/communication development. As reviewed previously, the more atypical the cognitive development, the more atypical the behavior is expected to be. As will be reviewed herein, in the continuum of developmental-behavioral disorders, this most dissociated and deviated pattern of language/social communication development is often accompanied by the most atypical neurobehavioral manifestations of what was defined in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) as “autistic disorder”³³ and is currently defined in DSM-5 as “autism spectrum disorder with a language disorder.”²⁸

The Spectrum of Nonverbal Dissociation and Deviation

When children evidence discrepant and disproportionate delays in their nonverbal visual-motor problem-solving development relative to their language development, their developmental diagnoses lie within the spectrum of nonverbal dissociation and deviation (see bottom portion of Figure 11.5). Of course, when a child presents with discrepant delays in visual-motor problem-solving development, primary pediatric health care professionals first need to formally confirm the child’s vision status prior to making a diagnosis within this spectrum. As one moves from the mild to the severe end of this spectrum, in addition to evidencing dissociated delays in more diffuse aspects of nonverbal visual-motor problem-solving abilities, increasing amounts of developmental deviation in the nonverbal domain are observed.

Visual-motor problem-solving development consists of multiple components, including visual-spatial perception, visual-motor integration, visual sequencing, visual memory, visual closure, and nonverbal communication. At the mild end of this spectrum, the dissociation in nonverbal visual problem-solving development involves a relatively focal deficit in orthographic processing, which involves the visual processing of letter identity and letter position within words.34 Children with orthographic processing deficits have difficulty with visual-spatial feature analysis, which initially results in difficulty in remembering the shapes of letters and how to use the correct sequence of strokes to form letters, and goes on to result in letter reversals (“b” and “d”) and reversals of whole words (“saw” for “was”) in reading and writing.^35,36 Children with orthographic processing disorders have difficulty with memorizing sight words, resulting in dyseidetic dyslexia, but they are able to sound out words, and they can spell phonetically, given their preserved language skills, including their preserved phonological processing.

While this chapter has described both dysphonetic and dyseidetic dyslexia as specific entities, and it will describe LLD and NVLD as specific entities, it is important to note that children may have mixed deficits in aspects of both phonological and orthographic processing, resulting in mixed dyslexia, or mixed deficits in aspects of both language-based and nonverbal-based learning, as in a mixed LD (see Figure 11.5 and Chapter 17, Learning Disabilities).

As more diffuse aspects of nonverbal visual problem solving become discrepantly delayed, nonverbal reasoning is negatively impacted, and a point is reached where nonverbal reasoning is found to be significantly below verbal reasoning on IQ testing. Such a significant discrepancy between nonverbal and verbal IQ is often classified as NVLD. Rather than evidencing a relatively isolated difficulty in the orthographic processing of letters and words, individuals with NVLD evidence more diffuse difficulties in visual-spatial, visual-perceptual, and visual-motor processing. Children with NVLD have deficits in the discrimination and recognition of visual detail and in visual-spatial orientation, including difficulties with right-left orientation, telling time on a clock, and reading maps. These children also have difficulty understanding spatial relations, including getting lost in familiar places and lacking appreciation of appropriate boundaries of interpersonal space. From an academic standpoint, children with NVLD have difficulties with the visual-spatial and conceptual aspects of mathematics (eg, aligning columns for multidigit calculations and geometry), and their visual-motor deficits negatively impact their writing.³⁶

As one moves toward the most severe end of the spectrum of nonverbal dissociation and deviation, increasing developmental deviation in the visual problem-solving domain tends to occur, and the dissociated delays in nonverbal abilities include discrepant delays in nonverbal pragmatic communication. Thus, despite their significant relative strengths in verbal ability and verbal reasoning compared to nonverbal reasoning, individuals at the severe end of this spectrum have deficits in the pragmatic/social use of nonverbal communication (difficulties with eye contact, maintaining a topic of conversation, taking turns during conversations, understanding figurative language, etc) that can be described as a social communication disorder without a language disorder. The nonverbal and social communication deficits at the severe end of this spectrum represent the most developmentally dissociated and deviated end of the nonverbal domain of cognitive development and thus represent the most atypical presentation of a nonverbal disorder. As reviewed previously, the more atypical the cognitive development, the more atypical the behavior is expected to be. As will be reviewed herein, in the continuum of developmental-behavioral disorders, this most dissociated and deviated pattern of nonverbal development is often accompanied by the most atypical neurobehavioral manifestations of what previously was defined in the DSM-IV33 as “Asperger disorder,” and what is currently defined in the DSM-5 as “autism spectrum disorder without a language disorder.”²⁸

The Spectrum of Neurobehavioral Dissociation and Deviation

It is essential to appreciate the wide behavioral variation of typically developing children and the importance of always interpreting behavior within the context of a child’s underlying developmental level and family, social, and cultural environments. However, neurobehavioral disorders are defined as disorders of behavior, thought, or emotion that are associated with dysfunction in the CNS. While this stream of development includes all of neuropsychiatry, the focus of this chapter will be the neurobehavioral domains of attention and activity level. As reviewed previously, within the spectrum and continuum of developmental-behavioral disorders, the processes of developmental dissociation and deviation are markers of increasing CNS dysfunction; behavior that is dissociated from cognitive expectations sits at the mild end of this spectrum of neurobehavioral disorders, while behavior that is deviated, or atypical at any age, sits at the severe end of this spectrum (see Figure 11.6).

Figure 11.6. Spectrum of neurobehavioral dissociation and deviation.

At the mild end of the spectrum of neurobehavioral dissociation and deviation are children whose levels of attention and activity are discrepantly delayed from what is expected based on their cognitive abilities, and these neurobehavioral difficulties impair the child’s functioning across settings. Children who exhibit this dissociation between attention span and/or activity level and cognitive expectations are at risk of a DSM-5 diagnosis of ADHD28 (see Chapter 18, Attention-Deficit/Hyperactivity Disorder).

As one moves to the more severe manifestations of this neurobehavioral spectrum, in place of the dissociated difficulties with inattention and easy distractibility observed in children with ADHD, a pattern of more developmentally deviated atypical attention is observed. Such deviated attention may be manifested by a short attention span that is present to such a severe degree that eye contact is difficult to maintain, while at the same time, the child becomes highly overfocused, and either visually or verbally perseverative, on repetitive behaviors or restricted interests.⁶ This significantly atypical attention may also be manifested by underfocus or overfocus on sensory stimuli, such as evidencing a high pain threshold or intolerance to certain noises, tightly fitting clothes, or food textures. Rather than evidencing the dissociated increased activity level and fidgetiness seen in ADHD, a child at the severe end of this spectrum may evidence more atypical and developmentally deviated stereotypic motor activity, such as hand flapping, body rocking, and spinning (see Figure 11.6).

As will be reviewed in the section on the continuum of developmental-behavioral disorders, it is important to note that these more atypical behavioral manifestations at the severe end of the spectrum of neurobehavioral dissociation and deviation are characteristically associated with the more atypical manifestations of the spectrum of cognitive dissociation and deviation. Given that increasing developmental delay, dissociation, and deviation within the cognitive stream of development signal increasingly atypical information processing, it should be expected that the more atypically an individual processes information, the more likely that the individual’s behavior will be similarly atypical. Thus, the repetitive and stereotyped behavior observed at the severe end of the spectrum of neurobehavioral dissociation and deviation is characteristically observed in continuum with either profound ID (significant global cognitive delay) or social communication disorders (significant dissociation and deviation in either language or nonverbal development).

The Continuum of Developmental-Behavioral Disorders

The continuum of developmental-behavioral disorders may be most easily conceptualized by the continuum across motor and cognitive streams of development at the severe end of each of these spectra. There is a significant continuum or overlap of disability across motor and cognitive streams, as approximately 50% of individuals with CP also have ID, and about 13% of individuals with ID also have CP.17 In addition, those individuals with CP who do not have ID are at higher risk than those without CP for other cognitive and neurobehavioral difficulties, including slower learning, LD, ADHD, and ASD.^17,37

Continuum Across Cognitive and Neurobehavioral Streams

There is also a continuum of developmental-behavioral disorders across cognitive and neurobehavioral streams of development at the mild end of each of these spectra (see Figure 11.7). Although an outdated term that has been generally discredited, the mild end of the cognitive and neurobehavioral continuum was previously described as representing minimal brain dysfunction.³⁸ This term implies mild but diffuse developmental-behavioral dysfunction across developmental streams.³⁹ Epidemiological research has supported this concept of mild but diffuse dysfunction across cognitive, neurobehavioral, and motor streams of development, as, for example, children with ADHD are much more likely than children without ADHD to have associated LD, gross motor clumsiness, handwriting difficulties, and speech articulation disorders.⁴⁰ Certainly, not every individual with ADHD evidences all of these comorbidities, but it is rare to identify an individual with ADHD who does not evidence some comorbid developmental or behavioral diagnoses (see Figure 11.7 and Chapter 18, Attention-Deficit/Hyperactivity Disorder).

At the severe end of the cognitive and neurobehavioral continuum lies what the DSM-IV termed the pervasive developmental disorders.33 While these disorders shared a pervasive primary deficit in reciprocal social interaction, this term was somewhat misleading, as the cognitive component of these disorders typically involved scattered, uneven, discrepant, dissociated, and deviated cognitive profiles, rather than pervasive cognitive delays across cognitive domains.^41,42 The pervasive developmental disorders, as defined in the DSM-IV,³³ included the diagnoses of autistic disorder, Asperger disorder, and pervasive developmental disorder not otherwise specified, but this classification was not retained in the DSM-5.²⁸ In the DSM-5, there is a single classification of ASD: What was “autistic disorder” in DSM-IV is now “autism spectrum disorder with a language disorder” in DSM-5, and what was “Asperger disorder” in DSM-IV is now “autism spectrum disorder without a language disorder” in DSM-5.^28,33

Within the spectrum and continuum of developmental-behavioral disorders, ASD consists of a continuum between the most developmentally dissociated and deviated cognitive profile observed in social communication disorders combined with the most developmentally deviated restricted, repetitive, and stereotypic behaviors observed at the severe end of the spectrum of neurobehavioral dissociation and deviation (see Figure 11.7). Children with ASD and a language disorder have social communication disorders at the severe end of the spectrum of language dissociation and deviation. In addition to their relative strengths in visual-motor problem solving and dissociated deficits in receptive and expressive language, these children also exhibit deviated reciprocal social interaction (impairment in reciprocal social interactions, lack of interest in peers, etc), dissociated delays in their verbal and nonverbal pragmatic/social communication (including difficulties with eye contact, response to name, greeting, requesting, and gestured communication), and deviation in their acquisition of language milestones (eg, having a 50-word vocabulary but not yet using a specific “Mama” or “Dada” to refer to their parents or continuing to use echolalia and to confuse pronouns when other [more rote and memorized] aspects of their language development extend beyond a 30-month level). Given their dissociated strengths in nonverbal visual problem-solving development, the repetitive behaviors and restricted interests of children with ASD and a language disorder typically include visually perseverative behaviors, such as lining up and sorting objects and visual perseveration on spinning objects, flashing lights, water flowing, or opening and closing doors repetitively. Their strengths in aspects of nonverbal visual problem solving might also be expressed through abilities in art, direction sense (ie, noticing changes in usual car routes), and visual memory. Consistent with this model of a spectrum and continuum of developmental-behavioral disorders, studies have confirmed that individuals with ASD with a language disorder (what used to be termed autistic disorder) tend to evidence dissociated delays in early language relative to visual problem solving development42–44 and often evidence language-based learning disabled cognitive profiles as they get older, with discrepancies between higher nonverbal IQs relative to lower verbal IQs.^45–48

Children with ASD without a language disorder have social communication disorders at the severe end of the spectrum of nonverbal dissociation and deviation. In addition to their dissociated nonverbal deficits, these children also exhibit deviated reciprocal social interaction and dissociated delays in their nonverbal pragmatic/social communication (including difficulties with eye contact, understanding and use of facial expressions and gestured communication, and visually “reading” social situations). Despite their relative verbal strengths, children with ASD without a language disorder (what used to be termed Asperger disorder) experience difficulty with speech prosody, taking turns during conversation, maintaining the topic of conversation, and understanding figurative language, including humor, sarcasm, and idioms. Given their dissociated strengths in language, the repetitive behaviors and restricted interests of children with ASD without a language disorder typically include verbally perseverative behaviors, such as engaging in pedantic, one-sided conversations that tend to list factual information about restricted interests, such as dinosaurs, train schedules, baseball statistics, or the weather. Consistent with this model of a spectrum and continuum of developmental-behavioral disorders, studies have confirmed that most individuals with ASD without a language disorder (what used to be called Asperger syndrome) evidence nonverbal learning-disabled cognitive profiles with discrepancies between higher verbal IQs relative to lower nonverbal IQs.^49,50

When reviewing the continuum of developmental-behavioral disorders, it is important to remember that diagnoses at the mild end of the continuum occur more commonly than those at the more severe end. For example, while LD and ADHD occur in approximately 7% to 8% of the population, ASD occurs in only 1.5% of the population.19,32,51 It is also important to note that developmental dissociation and deviation occur more commonly in the setting of developmental delay. For example, while most children with ID exhibit behavior consistent with their mental ages, they are at higher risk for both the dissociated neurobehavioral pattern of ADHD (30% of children with ID have ADHD versus 7.4% of children without ID).^18,51 and the dissociated and deviated social communication disorder cognitive profile and deviated neurobehavioral pattern of ASD (28% of children with ID have ASD versus a 1.5% prevalence in the general population).¹⁷ Figure 11.8 illustrates the entire spectrum and continuum of developmental-behavioral disorders described in this chapter.

Figure 11.8. Spectrum and continuum of developmental-behavioral diagnoses. Abbreviations: DQ, developmental quotient; IQ, intelligence quotient; LD, learning disability.

Conclusion

Developmental-behavioral disorders are the most prevalent chronic medical conditions encountered by primary pediatric health care professionals within the medical home; however, there is a dearth of pediatric subspecialists in the fields of neurodevelopmental disabilities and developmental-behavioral pediatrics to whom primary care professionals can refer their patients, and long waiting lists at tertiary care developmental evaluation centers. Thus, the vast majority of children with developmental-behavioral disorders need to be identified, diagnosed, and managed by their primary pediatric health care professionals within the medical home in collaboration with local early intervention and special education professionals. The AAP recommends the use of standardized developmental screening tests at specified ages,12 but it is important for primary pediatric health care professionals to know that while low-prevalence, higher-morbidity developmental-behavioral problems should be identified by early screening, much more prevalent mild developmental-behavioral problems may not be identifiable by screening at younger ages.¹³ In addition, while standardized screening and evaluation instruments certainly facilitate making accurate developmental and behavioral diagnoses, expert panels have endorsed that the clinical judgment of an experienced clinician is the gold standard for making developmental-behavioral diagnoses.¹⁶ Given the prevalence of these conditions in primary care practice, primary pediatric health care professionals need to be such experienced clinicians in this field. Certainly, in clinical practice, not every child with a developmental-behavioral concern always fits neatly into the diagnostic framework described in this chapter, and currently accepted diagnostic criteria need to be used when a specific developmental-behavioral disorder (eg, ASD, ADHD, LD, ID) is suspected. However, a thorough understanding of the key neurodevelopmental principles underlying the spectrum and continuum of developmental-behavioral disorders (as outlined in Box 11.1) may enhance clinical judgment and improve the confidence and diagnostic acumen of primary pediatric health care professionals in identifying children with developmental or behavioral disorders at the earliest possible age.

Box 11.1. Key Neurodevelopmental Principles

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