Essential of Diagnosis
Autism and the related pervasive developmental disorders are disorders of early onset in which abnormalities in the development of social interaction and communication are associated with problems in behavior and unusual sensitivity to the inanimate environment. Autism is the best known of these conditions. DSM-IV-TR criteria for it are listed in Table 34–1. In autism a marked and sustained impairment in social interaction is associated with delayed and deviant communication and restricted, stereotyped patterns of interest and behavior. The condition was first described by Leo Kanner in 1943. Kanner emphasized two key features: autism (social disinterest) and restricted interests and trouble with change. His report underscored the importance of the lack of social interest for other aspects of development and social factors are consistently identified as central to the diagnosis of the condition. In the first decades after its description, autism was often incorrectly assumed to be a form of schizophrenia. Only in 1980 was it officially recognized as a diagnostic category (Volkmar & Klin, 2005).
| Feature | Autism | Asperger | Rett | CDD | PDD-NOS |
|---|---|---|---|---|---|
| Social Disturbance | Severe | Moderate–severe | Variable | Severe | Variable |
| Language/Communication Impairment | Marked | Good verbal ability, poor communication | Very marked | Marked (previously normal) | Variable |
| Restricted interests | Marked, mannerisms, trouble with change, occasionally savant ability | Usually highly circumscribed interests (interfering with normal functioning) | Significant psychomotor retardation | Marked, as in autism | Variable—often troubled by change, Mannerisms may be less prominent |
| Motor issues | Often preserved early but poor later when imitation is required | Often clumsy, with fine and gross motor difficulties | Significant loss of motor abilities, hand-washing stereotypies | Often preserved but lose some self-care skills | Variable |
| Onset | Always before age 3 yr, often before age 1 yr. A minority regress after normal development | Problems often recognized in preschool. Motor delays may have been noted | Before age 5 yr (typically, onset with loss of skills) | By definition, child normal until age 2 yr; then major loss of skills and dramatic “autistic-like” picture | Variable |
A total of at least six items from (1), (2), and (3), with at least two from (1), and one each from (2) and (3):
Qualitative impairment in social interaction, as manifested by at least two of the following:
Marked impairment in the use of multiple nonverbal behaviors such as eye-to-eye gaze, facial expression, body postures, and gestures to regulate social interaction
Failure to develop peer relationships appropriate to developmental level
A lack of spontaneous seeking to share enjoyment, interests, or achievements with other people (e.g., by a lack of showing, bringing, or pointing out objects of interest to other people)
Lack of social or emotional reciprocity
Qualitative impairments in communication as manifested by at least one of the following:
Delay in, or total lack of, the development of spoken language (not accompanied by an attempt to compensate through alternative modes of communication, such as gestures or mime)
In individuals with adequate speech, marked impairment in the ability to initiate or sustain a conversation with others
Stereotyped and repetitive use of language or idiosyncratic language
Lack of varied spontaneous make-believe play or social imitative play appropriate to developmental level
Restricted repetitive and stereotyped patterns of behavior, interests, and activities, as manifested by at least one of the following:
Encompassing preoccupation with one or more stereotyped and restricted patterns of interest that are abnormal either in intensity or focus
Apparently compulsive adherence to specific, nonfunctional routines or rituals
Stereotyped and repetitive motor mannerisms (e.g., hand or finger flapping or twisting, or complex whole body movements)
Persistent preoccupation with parts of objects
Delays or abnormal functioning in at least one of the following areas, with onset prior to age 3: (1) social interaction, (2) language as used in social communication, or (3) symbolic or imaginative play
Not better accounted for by Rhett disorder or childhood disintegrative disorder
(Reprinted, with permission, from Diagnostic and Statistical Manual of Mental Disorders, 4th edn. Text Revision. Copyright 2000 American Psychiatric Association.)
The term “pervasive developmental disorder (PDD)” was coined in 1980 as the overarching term for a class of disorders to which autism was then assigned. The term is essentially synonymous with “autism spectrum disorders.” The current diagnostic system includes other conditions within this class including Asperger syndrome (social disability but with good verbal skills), childhood disintegrative disorder (a rare condition in which a condition like autism develops after a period of normal development), Rett disorder (a neurodegenerative disorder with a strong genetic basis), and pervasive developmental disorder not otherwise specified (PDD-NOS). The latter is, somewhat paradoxically, the least well defined of the PDDs and least frequent studied, yet the most common type. The clinical features of the PDDs are summarized in Table 34–1.
General Considerations
The first studies of epidemiology reported a prevalence rate of 4.5 per 10,000. Subsequent studies have tended to report higher rates, on balance around 9 children per 10,000. Although there has been much interest in higher rates in recent years, that is, whether the frequency of autism is increasing, several factors make it difficult to interpret the nature of the apparent increase. For example, diagnostic criteria have changed and current approaches were designed to work well in children over the range of cognitive ability levels. Secondly, rates reported vary depending on other factors, (e.g., sample size, with highest rates in reported in the smallest samples). There is also more general awareness of the condition. Given the importance of labels for service delivery (particularly in the United States), diagnostic substitution (e.g., assignment to PDD rather than mental retardation) can be problematic particularly for studies based on reports from schools and service providers.
In Kanner’s first paper, many parents of autistic children were remarkably successful, leading to the impression of an association between social class and autism. However, subsequent studies have failed to reveal such an association. It appears that Kanner’s initial sample reflected referral bias. Ethnic and cultural issues have been little studied in autism. While current diagnostic criteria appear to work well, there may be major differences in treatment. Gender differences have been consistently reported in autism, boys being 3–4 more times more likely than girls to have autism. However, this disparity is more marked at the upper end of the IQ distribution and, conversely, the ratio is less among children with more severe cognitive disability. This might either reflect a lower threshold for brain dysfunction in males or the fact that factor(s) causing autism in females must be more severe (Fombonne, 2005).
In the first decades after autism was identified, there was much speculation that experiential factors might be involved in autism. However, as time went on, evidence (e.g., high rates of seizure disorder, persistence of primitive reflexes, “soft” neurological signs) suggested brain involvement. When the confusion between autism and schizophrenia was clarified, the focus began to shift toward brain and genetic mechanisms.
