Clinical Manifestations

The core features of autistic disorder (AD) include impairments in 3 symptom domains: social interaction; communication; and developmentally appropriate behavior, interests, or activities (Table 28-2). Stereotypical body movements, a marked need for sameness, and a very narrow range of interests are also common.

Aberrant development of social skills and impaired ability to engage in reciprocal social interactions are hallmark symptoms of AD. Early social skill deficits can include abnormal eye contact, failure to orient to name, failure to use gestures to point or show, lack of interactive play, failure to smile, lack of sharing, and lack of interest in other children. Some children with AD make no eye contact and seem totally aloof, whereas others show intermittent engagement with their environment and can make inconsistent eye contact, smile, or hug. Most children have some impairment in joint attention, which is the ability to use eye contact and pointing for the purposes of sharing experiences with others. These children show deficits in empathy for what another person might be feeling. They also demonstrate deficits in understanding what another person might be thinking, a lack of a theory of mind.

Children with AD vary in their verbal abilities. They can range from being nonverbal to having some speech (e.g., capable of imitating songs, rhymes, or television commercials). Speech might have an odd prosody or intonation and may be characterized by echolalia (imitative repetition of words), pronoun reversal, nonsense rhyming, and other idiosyncratic language forms. Early abnormal language concerns include absent babbling or gestures by 12 mo, absent single words by 16 mo, absent 2-word purposeful phrases by 24 mo, and any loss of language or social skills at any time.

Play skills in AD are typically aberrant, characterized by little symbolic play, ritualistic rigidity, and preoccupation with parts of objects. The child with AD is often withdrawn and spends hours in solitary play, often with restrictive or repetitive interests and behaviors. Ritualistic behavior prevails, reflecting the child’s need to maintain a consistent, predictable environment. Tantrum-like rages can accompany disruptions of routine.

Intellectual functioning can vary from mental retardation to superior intellectual functioning in select areas (splinter skills, savant behavior). Some children show typical development in certain skills and can even show areas of strength in specific areas, such as puzzles, art, or music.

Visual scanning of hand and finger movements, mouthing of objects, and rubbing of surfaces can indicate a heightened awareness of and sensitivity to some stimuli, whereas diminished responses to pain and lack of startle responses to sudden loud noises reflect lowered sensitivity to other stimuli.

Diagnosis

AD is diagnosed by the clinical examination. The gold standard diagnostic tools are the Autism Diagnostic Interview—Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS), which require referral to a trained professional for administration.

Neuropsychologic and achievement assessment should include intelligence testing to establish overall cognitive function and eligibility for services. Intelligence, as measured by conventional psychologic testing, falls in the functionally retarded range in 30-60% of children with AD. Deficits in language and socialization often make it difficult to obtain an accurate estimate of a child’s intellectual potential. Some children with AD perform adequately in nonverbal tests, and those with developed speech can show adequate intellectual capacity. Separate estimates of verbal and nonverbal (performance) intelligence quotient (IQ) should be obtained. A measure of adaptive functioning such as the Vineland Adaptive Behavior Scales is essential to establish priorities for treatment planning.

Critical elements of the evaluation should include a detailed developmental history with a review of communicative and motor milestones, a medical history including discussion of possible seizures, sensory deficits such as hearing or visual impairment, or other medical conditions associated with AD including fragile-X, Prader-Willi, Smith-Lemli-Opitz, Rett’s, and Angelman’s syndromes, fetal alcohol syndrome, tuberous sclerosis, neurofibromatosis, congenital rubella, or untreated phenylketonuria. The family history should be reviewed for the presence of other developmental disorders. A review of current and past psychotropic medications should include a review of medication dosages and behavioral response, along with adverse effects. The impact of other medications on behavioral status should also be reviewed.

The medical and genetic evaluation of children with PDD must consider a broad range of disorders (Table 28-3). Approximately 20% of children with AD have macrocephaly, but enlarged head size might not be apparent until after the 2nd yr of life. In the absence of dysmorphic features or focal neurologic signs, additional neuroimaging for investigation of macrocephaly is not usually indicated. Multidisciplinary assessment of AD is optimal in facilitating early diagnosis, treatment, and coordinated multiagency collaboration. Evaluations from various other professionals, including a developmental pediatrician or pediatric neurologist, medical geneticist, child and adolescent psychiatrist, speech-language pathologist, occupational or physical therapist, or medical social worker may be indicated.

Differential Diagnosis

The differential diagnosis includes consideration of the various PDD, mental retardation not associated with PDD (Chapter 33), specific developmental disorders (e.g., of language), early onset psychosis (e.g., schizophrenia), selective mutism, social anxiety (Chapter 23), obsessive-compulsive disorder, stereotypic movement disorder, inhibited-type reactive attachment disorder, and rarely, childhood-onset dementia.

Epidemiology

The incidence of AD has increased steadily over the past 15 yr. There is evidence that the increase in the number of children identified with AD is likely related to changes in the definition of and diagnostic criteria for AD, as well as improvements in the recognition of AD at younger ages. Current estimates of the prevalence rate of all PDD (63.7/10,000) are approximately 1 in 150-160. Disorder-specific prevalence rate estimates includes AD (20.6/10,000), Asperger’s disorder (6/10,000), PDD-NOS (37.1/10,000), Rett’s disorder (0.5-1/10,000 females), and childhood disintegrative disorder (2/100,000). The male : female ratios are estimated to be 4 : 1 for AD and 5 : 1 for Asperger’s disorder.

Pathology

Retrospective analysis of head circumference, in conjunction with MRI studies, has shown differences in the brain structure of children with AD. The head circumference in AD is normal or slightly smaller than normal at birth until 2 mo of age. Afterward children with AD show an abnormally rapid increase in head circumference from 6-14 mo of age, increased brain volume in 2-4 yr olds, increased volume of the cerebellum, cerebrum, and amygdala, and marked abnormal growth in the frontal, temporal, cerebellar, and limbic regions of the brain. Early, accelerated brain growth during the 1st several years of life is followed by abnormally slow or arrested growth, resulting in areas of underdeveloped and abnormal circuitry in parts of the brain. Areas of the brain responsible for higher-order cognitive, language, emotional, and social functions are most affected.

Etiology

The basis for AD is diverse and complex. Multiple genetic regions (chromosomes 16p11.2, 15q24, 11p12-p13) and gene variants (copy number variation, deletions, microdeletions, duplications, inversions, translocations) potentially contribute to abnormal neuronal and axonal growth, synapse formation, and myelination via gene-gene and gene-environment interactions over the course of prenatal and postnatal development. Inheritance patterns of AD demonstrate a 60% concordance rate for monozygotic twins and no concordance in dizygotic twins. A 4 : 1 male : female AD prevalence ratio suggests a sex-linked mechanism in a significant number of cases. An emerging etiologic hypothesis of AD describes spontaneous paternal or maternal genetic mutations that delete or inactivate areas of the genome affecting early brain development.

In utero toxic insults are also thought to carry the potential to produce disruptions in CNS development that can manifest as mental retardation and autistic symptoms. There is no scientifically substantiated association between the administration of the measles-mumps-rubella vaccine and the development of AD. As yet undiscovered environmental factors cannot be ruled out. There may be genetic associations between AD and premature birth as well as childhood-onset schizophrenia, suggesting possible common core neurobiologic processes for subsets of these two heterogeneous clinical groups.

Early Identification

Early identification and intervention of PDD are associated with better outcomes. Several instruments have been developed for screening of PDD in primary care settings including the Checklist for Autism in Toddlers (CHAT), the Modified Checklist for Autism in Toddlers (M-CHAT), and the Pervasive Developmental Disorders Screening Test (PDDST) (Chapter 18) (Fig. 28-1). Failures to meet age-expected language or social milestones are important early red flags for PDD and should prompt an immediate evaluation. Early signs include unusual use of language or loss of language skills, nonfunctional rituals, inability to adapt to new settings, lack of imitation, and absence of imaginary play. Deviations in social and emotional development (such as decreased eye contact, failure to orient to name, and lack of joint attention) can often be detected by 1 yr of age. The absence of expected social, communication, and play behavior often precedes the emergence of odd or stereotypical behaviors or the unusual language usage that is seen in AD in the later years.

Figure 28-1 Surveillance and screening algorithm: autism spectrum disorders (ASDs).

(From Plauche Johnson C, Myers SM, Council on Children with Disabilities: Identification and evaluation of children with autism spectrum disorders, Pediatrics 120:1183–1215, 2007.)

Treatment

The primary goals of treatment are to maximize the child’s ultimate functional independence and quality of life by minimizing the core features of the disorder, facilitating development and learning, promoting socialization, reducing maladaptive behaviors, and educating and supporting families. Educational interventions, including behavioral and habilitative (speech, occupational, and physical) therapies, are the cornerstones of treatment for the PDDs. These interventions address communication, social skills, daily-living skills, play and leisure skills, academic achievement, and maladaptive behaviors.

Model early childhood educational programs for children with PDD can be categorized as behavior analytic, developmental, or structured teaching on the basis of the underlying theoretical orientation. Although programs differ in relative emphasis, they share many common goals, including beginning intervention as early as possible; providing intensive intervention (at least 25 hr/wk, 12 mo/yr) in systematically planned educational activities; providing a low student-to-teacher ratio; including parent training; promoting opportunities for interaction with typically developing peers incorporating a high degree of structure through elements such as a predictable routine, visual activity schedules, and clear physical boundaries; implementing strategies to apply learned skills to new environments and situations; and using curricula that address functional spontaneous communication, social skills, functional adaptive skills, reduction of maladaptive behaviors, cognitive skills, and traditional academic skills. Some well-regarded programs that address at least some of these skills include Applied Behavioral Analysis (ABA), Discrete Trial Training (DTT), and Treatment and Education of Autistic and related Communication-handicapped Children (TEACCH). Most educational programs available to young children with PDDs are based in communities in the context of an Individualized Education Program (Chapter 15), and offer an eclectic treatment approach, which may be less effective than standardized protocols.

Parent training and family involvement includes educating parents about PDDs, providing access to needed ongoing supports and services, training and involving them as co-therapists, assisting them in advocating for their child’s needs, and providing emotional support.

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