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Autism and Pervasive Developmental Disorders
I
Autism and Pervasive Developmental Disorders
I. II. III. IV. V. VI. VII. VIII. IX.
Deborah Fein and LeeAnne Green
Lynn Waterhouse
University of Connecticut
The College of New Jersey
Historical Development of the Concept of Autism DSM-IV Criteria Behavioral and Cognitive Characteristics Developmental Course and Prognosis Epidemiology Boundary Conditions and Comorbidity Biological Factors Clinical Assessment Treatment
PERVASIVE DEVELOPMENTAL DISORDERS (PDD) is the current term for what is probably a group of related neurodevelopmental disorders characterized by similar behavioral profiles. Autistic Disorder is the most widely studied and best described of these disorders. It is characterized by deficits in social relatedness, deficits in language and communication, and stereotyped and restricted patterns of behavior, and is frequently but not always accompanied by mental retardation.
Echolalia Parrot-like repetition of utterances either immediately after hearing the utterance (immediate echolalia) or at a later time (delayed echolalia). Gaze Avoidance The tendency to avert one's eyes in order to avoid eye-to-eye contact with another. Mainstreaming The integration, or partial integration, of a child with special needs into a classroom of typically developing children. Metaphorical Language Idiosyncratic utterances whose meaning is clear only to those who are familiar with the child's history. Pragmatics The social aspects of language, or the communicative uses to which language is put. Stereotypies Repetitive and often unusual motor movements. Stimulus Overselectivity A tendency to attend to a restricted portion of a stimulus array or a complex stimulus. Theory of Mind An understanding or concept of the existence of mental representations, including knowledge and perspective, in others.
I. HISTORICAL DEVELOPMENT OF THE CONCEPT OF AUTISM Autism was first described by Leo Kanner in 1943 and became known as Infantile Autism or Autistic Disorder. The concept has expanded since that date, and the term "Kanner autism" is sometimes used to refer to cases with symptoms similar to those of Kanner's original sample; such cases are a subset of PDD. Kanner's original description remains influential, and there is a tendency in the literature to assume that persons with "Kanner autism" represent the "nuclear" or "core" form of PDD, an assumption that may not be warranted. Kanner identified symptoms in three main groups: an autistic aloneness, a failure to use language communicatively, and an obsessive insistence on sameness in the environment; these are still the three areas of symptomatology used in current diagnostic systems. Although Kanner originally viewed the autis-
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Copyright 9 1998 by Academic Press. All rights of reproduction in any form reserved.
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tic aloneness as probably representing a constitutional defect, the two decades following his original work were marked by an unfortunate shift toward a psychodynamic/environmental view of the causation of autism. This served to derail any significant progress in understanding the disorder, as well as to cause a great deal of additional anguish to parents of autistic children. Beginning with Rimland's seminal work on autism in 1964, psychology and psychiatry began to explore seriously the biological foundations of autism, and theories of autism as resulting from disturbances in attention, language, sensory integration, perceptual constancy, and other neurological functions were promulgated and tested. Beginning in the early to mid1980s, research attention also began to focus seriously on the social and affective aspects of autism, both to clarify the range of heterogeneity in autistic children's functioning, and to posit new core deficits in these areas. Currently, researchers stressing both cognitive and social/affective deficits as primary are in agreement that the fundamental problem is a neurological, and not an environmental, one. Differential diagnosis was a conceptual problem for early autism research. Some clinicians believed that autism was a variant of or precursor to schizophrenia. Only in the 1970s came an awareness that disorders beginning in infancy must be regarded as separate in kind from those with onset in later childhood, adolescence, or adulthood. Autistic-like disorders virtually always begin before age 3, while schizophrenic-like disorders virtually never begin before age 7. This realization revitalized interest in infantile autism as a distinct nosologic entity, leading to the development of more operationally precise diagnostic criteria and a reconceptualization of the syndrome as a pervasive developmental disorder, under which label it was incorporated by the American Psychiatric Association in the third edition of that body's Diagnostic and Statistical Manual of Mental Disorders (DSM-III ); this conceptualization has been retained in DSM-III-R and DSM-
IV. [See SCHIZOPHRENIA.]
II. DSM-IV CRITERIA Current diagnostic practice, as reflected in the DSMIV, classifies Autistic Disorder as one of four specific
entities within Pervasive Developmental Disorder. Autistic Disorder is marked by the presence of symptomatology in three areas: (1) qualitative impairment in social interaction, as manifested by such behaviors as abnormal or reduced eye contact with others, failure to develop peer relationships, lack of spontaneous sharing of interests with others (e.g., showing or pointing out objects of interest to the caregiver), (2) qualitative impairment in communication, as manifested by delayed or deviant language without attempts to compensate through nonverbal communication, poor conversational skills if speech is present, and repetitive and stereotyped language and play, and (3) a restricted and repetitive repertoire of behaviors and interests, including preoccupations and rituals, or severe resistance to environmental changes. The specific behavioral manifestations of these traits differ by degree of accompanying retardation and age. A high-functioning, older autistic individual, for example, may attempt to be social, but violate implicit rules of social behavior and be insensitive to unspoken social signals, while a low-functioning or much younger autistic individual may react to other people as if they were little different from inanimate objects. Similarly, a high-functioning, older autistic individual may have perseverative interests in such topics as constellations, train schedules, or dinosaurs, and attempt to engage others in conversations on these subjects, while a lower functioning or younger autistic individual might engage in repetitive motor rituals. The other specific syndromes classified as Pervasive Developmental Disorders include Rett's Disorder, Asperger's Disorder, and Childhood Disintegrative Disorder. Rett's Disorder has marked behavioral commonalities with Autistic Disorder, including poor social engagement and mental retardation, but differs from Autistic Disorder in several ways: in Rett's Disorder, the retardation is more invariant and more typically severe, the disorder seems to present only in girls, it is marked by a characteristic pattern of head growth deceleration and loss of purposeful hand movements, sometimes accompanied by hand wringing behavior, following a period of normal development. Many girls with Rett syndrome also have epilepsy and other neurologic abnormalities. Asperger's Disorder is often considered a mild form of Autistic Disorder, and there is still controversy about how distinct it is from autism;
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diagnostically, it can be distinguished from autism by normal development of language. Childhood Disintegrative Disorder differs from Autistic Disorder in that the former is marked by a distinctive pattern of developmental regression following at least two years of normal development. This disorder is much rarer than autism, and controversy exists here, too, about the etiological and phenomenological distinctiveness between Childhood Disintegrative Disorder and Autistic Disorder. [See MENTAL RETARDATION AND MENTAL HEALTH.]
III. BEHAVIORAL AND COGNITIVE CHARACTERISTICS A. Behavioral Characteristics in Autism I. Social Behavior Social behavior is considered by many as the hallmark of autism. As with all features of autism, social impairment is highly heterogeneous; it varies with age, with IQ, with setting, and with interactive partner, and is modifiable by treatment. Social impairment is generally most severe in the preschool years; it is in early childhood that genuine aloofness is seen. Older children may initiate interaction to get their needs met, or may be responsive but noninitiating to others. Older or higher-functioning autistic individuals may approach others in an idiosyncratic, intrusive, and socially insensitive way. These three general styles (aloof, passive, active-but-odd) form the basis of a social typology described by Lorna Wing, and validated by several later studies. Highly structured settings with enforced proximity to peers may elicit the best peer interactions. Relationships with other children are almost always more impaired than the corresponding behavior with adults; other children may be ignored when adults are not. Behavioral deficits in social interaction are varied; among the most important, especially in early life, are (1) poor spontaneous imitation of others' language and behavior, (2) gaze avoidance or other deficits in the use of eye-to-eye gaze to modulate or initiate interaction, and (3) deficits in various joint attention skills, including drawing an adult's attention to an object of interest by showing or pointing, and following an adult's attentional focus in order to share it. On the
other hand, the "pervasive lack of responsiveness" described in DSM-III is actually uncommon; many young autistic children are selectively attached to their parents, derive comfort from their presence, and enjoy physical affection.
2. Communication and Play Older studies were composed primarily of clinical descriptions of language features such as pronoun reversal, echolalia, and metaphorical language. More systematic studies have appeared, based on modern understanding of the separable components of language. The more severely affected autistic child may remain nonverbal or minimally verbal and poorly intelligible. In those who develop more language, phonology, syntax, and (more arguably) semantics are relatively spared, although still often at a lower level than nonverbal skills. Verbal memory, prosody, and pragmatics, on the other hand, represent areas of particular difficulty for the average autistic child. In the domain of pragmatics, it is noted that communicative functions are generally more need-oriented and less affiliative, and that violations of language use rules are common, such as violations of implicit rules concerning interpersonal distance while speaking, and the rules of turn-taking in conversational exchange, as well as word selection which is overly formal or pedantic. Symbolic play is also often observed to be lacking in young autistic children, who sometimes prefer nonsymbolic play activities such as puzzles or other manipulatives. When symbolic play develops, it can be unusually repetitive and inflexible in nature. Some recent evidence suggests that high-functioning autistic children may be not so much incapable as uninterested in engaging in frequent or complex symbolic play.
3. Preoccupations, Perseverations, and Resistance to Change These constitute the third symptom group. These behaviors range from simple or complex motor stereotypies, to "self-stimulatory" sensory behaviors such as watching fans or water, to long-term perseverative interests. The resistance to change is manifested by tantrums or other extreme reactions to changes in environmental features or in routines. Despite the equal role assigned to perseverations/preoccupations and resistance to change in diagnostic criteria, some
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recent data suggest that resistance to change is a less common feature of autism than perseverations/preoccupations.
B. Cognitive Characteristics Overall cognitive level, or presence of mental retardation, is an important feature of the individual autistic child, and powerfully predicts the functional outcome that can be expected for the child. Recent work by several research groups, such as the group headed by Rapin (see Bibliography) suggests that high- and low-functioning autism may be significantly different in behavioral manifestations, history, and prognosis, that approximately half of the autistic population falls into each group, and that an IQ cutoff of about 65 makes the most appropriate division between highand low-functioning autism. Beyond studies of overall cognitive level, many investigators have examined typical cognitive profiles in autism, that is, areas of relative sparing and impairment. Some autistic children, both those with severe impairment and those who are higher functioning, display unusual gifts, especially in rote memory, calculations, and music. A majority of autistic children are known to have relative strengths in visuospatial abilities, while tasks requiring verbal reasoning, social cognition, or flexibility pose relative difficulty for the autistic child. Although this description suggests a typical cognitive profile, studies have shown that there is great heterogeneity in the autistic population, and that no single cognitive deficit is universal in autistic individuals.
I. Language The autistic child's language profile is arguably the syndrome's most distinctive cognitive feature, which has earned it a central position in some theories of the etiology of autism. Many aspects of verbal functioning are impaired in autistic children, as many as 40 to 50% of whom are mute, although this figure is declining with the advent of aggressive early intervention. Those with speech often display echolalia, difficulties with prepositions and pronouns, and inappropriate conversational behaviors. Verbal autistic children generally are able to acquire normal grammatical morphology and syntax, although onset and development are delayed. Some autistic children learn
grapheme-phoneme correspondence, leading to early decoding of words; comprehension, however, lags far behind. Comprehension of oral language is significantly impaired relative to expression, and deficits in the semantic and pragmatic aspects of language are common. They are also deficient in interactive communication, including conversational behavior, nonverbal communication and speech prosody. In general, the more linguistic aspects of communication, including especially phonology and syntax, are spared relative to the pragmatic aspects; pragmatic deficits can be seen in the failure to use language functionally to share or request information, or perform other speech functions that serve social, rather than instrumental, functions.
2. Social Cognition A decade of research has documented substantial deficits in autistic children's ability to understand the behavior, emotions, and cognitive states of other people. They have difficulty in matching pictures of emotional facial expressions to emotion words, to emotional situations, to similar expressions, and to vocal expressions of the same emotion. Much recent interest has been stimulated by exploration of autistic performance on "theory of mind" tasks; in a typical theory of mind task, the subject is asked to predict behavior of a doll in a social scenario. The behavior can only be correctly predicted if the subject has a true theory of mind, that is, truly understands the concept of others' minds, with their own representational capacities, and their own limits on available knowledge. Autistic subjects have been shown to be impaired on these tasks in several studies. A cautionary note here, however, about all of these social cognitive tasks is that many higher functioning autistic individuals do well on them; the deficits are far from universal. Furthermore, verbal IQ explains much of the variance in performance. Therefore, it remains to be demonstrated that deficits in social cognition, including theory of mind, occupy a key causal role in the syndrome; they may be more a concomitant deficit related to the overall social impairment, although opinions differ widely on this.
3. Attention Unusual attentional processes are characteristic of autistic children. Autistic children are generally able to
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sustain attention in tasks adequately when given potent reinforcement or when the task is of interest to them, and higher functioning individuals are able to perform well on standard neuropsychological tests of sustained attention. In contrast, many autistic children appear to have difficulty with tasks requiring the focusing and shifting of attention. They are found to be overseiective in their attention to particular parts of stimuli, and studies indicate that they may have difficulties in shifting attention between stimuli, especially across sensory modalities, perhaps contributing to the perseveration so characteristic of their behavior.
4. Memory Memory abilities in autism have not been as fully investigated as other cognitive functions. Anecdotally, amazing feats of memory have been reported, where autistic individuals recall distant episodes with great clarity and detail; hyperdeveloped memory for stimuli such as routes, spatial arrays, schedules and calendars, and music have also been frequently reported. Tested memory for visual material in high-functioning autistic individuals is often normal. In contrast, memory for linguistic and social material is usually impaired. Autistic individuals appear not to be able to use the intrinsic semantic structure of discourse or stories to aid recall, and in this regard, are more impaired than children with specific language disorders.
5. Executive Functions Executive functioning refers to the higher level cognitive processes of abstract conceptualization, planning, problem solving, and self-monitoring, self-correction and self-control. These processes are thought to be localized to prefrontal cortex, and are assessed with standardized neuropsychological tests developed for evaluation of frontal functions. Some autistic individuals have great difficulty with these tasks, especially in switching from incorrect strategies during tasks. Some researchers have noted similarities between certain symptoms of autism and those of patients with frontal lobe damage (e.g., perseveration, lack of inhibition), and have proposed that frontal executive system impairment causes distinct social cognitive deficits. Furthermore, some findings suggest that executive system adequacy may predict outcome for autistic adolescents better than measures of IQ.
IV. DEVELOPMENTAL COURSE AND PROGNOSIS Autism, as a developmental disorder, cannot be fully described at a single developmental point. The typical description of the autistic child is that he or she lacks interest in relating to others and lacks communicative language. These symptoms are most characteristic of autistic children in the preschool years. Even during this period, there are often signs of increasing social relatedness, especially to caretakers. On the other hand, stereotypies and especially resistance to change, may appear in the preschool years or somewhat later. During middle childhood, autistic children often master some daily living and academic skills and make behavioral adjustments to their parents and teachers. Their behavior may come to resemble that of hyperactive and/or retarded children, or they may develop into socially motivated children, who relate in an odd or idiosyncratic way, with deficits in emotional reciprocity. Early and middle adolescence can be particularly difficult. Besides the onset of seizures that sometimes occurs in early adolescence, a significant minority of PDD children regress behaviorally and even cognitively at this time. Some autistic adolescents show increasing interest in developing peer relationships during these years. Higher functioning individuals with PDD are prone to psychiatric problems, especially anxiety and depression, as they realize the extent of their difference from peers. On the positive side, both social and language skills often continue to improve during adolescence, and even those children who regress during early adolescence may recover and make developmental progress toward the middle or end of adolescence. Increasing interest in relating to other people can also set the stage for psychosocial interventions or behavioral skill training to be more effective. Long-term follow-up studies indicate great variability in adult outcomes, but a generally guarded prognosis for good adjustment must be the rule. About half of all autistic adults require residential care; many of the remainder depend on relatives for daily assistance. Gainful employment and fully independent living may be achieved by about one in five. Even for the best-outcome group, social difficulties remain common, marriage or sexual relationships rare, and many social relationships revolve around work or struc-
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tured activities and interests. It should be noted, however, that the generation of children who have received the benefit of modern special education and behavioral interventions have not yet reached adulthood, and their outcomes, it is hoped, will be significantly better. Follow-up studies are consistent in demonstrating that higher IQ and communicative language by the age of 5 are strong predictors of better outcome, associated neurological signs and symptoms are predictors of poorer outcome.
V. EPIDEMIOLOGY Prevalence rates vary according to the definition of the syndrome. Earlier and more restrictive definitions of autism yielded prevalence estimates of 2-4/10,000. Broader definitions encompassing the full PDD spectrum suggested rates three or more times greater. Recent estimates have increased. This may be attributable to improved detection, more lenient diagnoses, or actual increases in prevalence. Most recent estimates are approximately 10/10,000 for PDD disorder, including autism, and another 10/10,000 with a more broadly defined triad of deficits in social relatedness, communication, and stereotyped behavior plus mental retardation. PDD spectrum disorders are more common in males than in females, with ratios found between 2:1 and 10:1, the higher ratios applying more to the Asperger-type clinical picture.
VI. BOUNDARYCONDITIONS AND COMORBIDITY Specifying the boundary between autism and other PDD spectrum disorder (such as Rett's and Asperger's Disorder), mixed language disorder, or severe mental retardation can be problematic, and differential diagnoses among these conditions can be difficult. Although diagnostic definitions of autism and language disorder appear distinct, in practice, the differential diagnosis can be unclear, especially in preschool children. Studies from Rutter and colleagues in the 1970's and from Rapin's group indicate that the diagnostic groups can be distinguished not only by the presence of autism-related behaviors, but by differences in the
language domain itself. The autistic children tend to have greater delays and deficits in language comprehension than the language-disordered children; in the expressive domain, delayed appearance of Wh-questions is highly discriminating. Regression of acquired language skills is also much more typical of autism, but also characterizes children with Landau-Kleffner syndrome. Landau-Kleffner syndrome, also referred to as acquired epileptic aphasia, refers to loss of language in a child in the context of clinical seizures or a frankly epileptiform EEG. There is disagreement as to whether the term should be reserved for children who have no serious associated behavior or cognitive disorders, or whether the term should be broadened so as to include those children who also develop autistic behaviors or become frankly autistic. Autism may also have increased comorbidity with specific additional disorders. Although still controversial, some investigators present evidence that there is a greater than chance coincidence of autism and Tourette's disorder. When tics occur in autism, they tend to occur in high-functioning autism. The relationship between autism and schizophrenia also remains a matter of debate. At one time, the two disorders were believed to be related, but different ages of onset, patterns of symptomatology, and family histories have convinced many investigators that they are unrelated. Nevertheless, reports exist of schizophrenia developing in previously autistic individuals at a greater than chance rate, and a small number of researchers believe that autism is a particularly early and severe form of childhood schizophrenia. Autism is also related to the presence of seizure disorders. About half of autistic individuals have clinical seizures and/or abnormal EEGs. Infancy and adolescence are high-risk periods for the appearance of seizures. All types of seizures occur; generalized tonicclonic are the most common.
VII. BIOLOGICAL FACTORS A. Associated Biomedical Conditions and Genetic Factors Several specific medical conditions are associated with autism, including phenylketonuria, rubella embryopathy, herpes encephalitis, fragile X syndrome, and neurocutaneous disorders such as tuberous sclerosis.
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Some studies estimate that between one-eighth and one-fourth of autistic children have an associated medical condition, but it is not known whether these conditions play a causal role in the development of autistic symptoms. Of possible prenatal factors, maternal rubella is most commonly associated with autism, the prevalence for which is 100 times that for the general population. Other obstetrical factors are found more frequently in autistic children than in other populations, particularly midpregnancy maternal bleeding. The fragile X genetic syndrome has been identified in an estimated 2 to 10% of the autistic population. Fragile X is a rare X-linked syndrome (most prevalent in boys) that involves intellectual impairment, attention deficits, and identifying physical features (prominent ears, long and narrow face, and macroorchidism). Within the fragile X population, it is estimated that 15 to 30% have autistic features, which are qualitatively distinct compared with those seen in the "typical" autistic child. Fragile X autistic children have been found to show perseverative speech as opposed to echolalia, and display active-but-odd social behaviors rather than aloofness. The specific route of pathology connecting fragile X to the expression of autistic symptoms is unknown. A genetic basis for at least some forms of autism has been demonstrated by family studies. Approximately 3 % of families with an autistic child will produce another child with autism, a prevalence rate which equals 50 to 100 times that of the general population. In addition, the concordance rate for autism in monozygotic twins has been found to range from 40 to 96%. Further support for genetic involvement is found in studies of characteristics in families of autistic children. Siblings of autistic children may be more likely to show superiority in visuospatial over verbal abilities (analogous to the autistic profile), cognitive difficulties such as language disorder, and social disengagement. A few studies have found that some parents of autistic children may be more likely to show unusual social behaviors. The search for specific genetic markers for autism thus far has uncovered two prospects: a marker for a gene that regulates neuron development, and abnormalities of chromosome 15. Taken together, studies suggest that at least a subset of autistic cases are attributable to genetic origin, either familial or mutational. The incidence of autistic
symptoms in medical conditions that are not genetic, however, suggests that the PDD spectrum may represent a variety of etiologies ultimately affecting common brain systems.
B. Neuroanatomical Findings Studies of neuroanatomical abnormalities in autistic patients have relied mainly upon postmortem neuropathology examinations and imaging techniques such as positron emission tomography (PET), computerized tomography (CT) and magnetic resonance imaging (MRI). They have generally focused on cortex, brainstem, limbic areas and cerebellum, and have found great variability in brain pathology. Gross cortical and ventricular abnormalities, for example, have been found in some cases and not others. Two structures of great interest are the amygdala and hippocampus, which are limbic structures involved in social/emotional behaviors and in memory. Abnormalities in limbic areas of the brain have been implicated in several studies, most notably in detailed postmortem examinations performed by Bauman and Kemper. These and other studies have also found abnormalities in the cerebellum, although the nature of these cerebellar abnormalities is not consistent across studies.
C. Neurophysiological Findings Findings from PET studies of regional cerebral blood flow have suggested diminished temporal lobe activity, and possible delayed frontal lobe maturation in autistic children. PET studies of regional glucose metabolism, which reflects brain energy utilization, have indicated abnormal patterns of regional activation. Several others have found global glucose hypermetabolism in autistic patients, which was thought to reflect inefficient processing. This feature, however, is not unique to autism. Studies examining brain waves and oculomotor activity in REM sleep have suggested a developmental immaturity of brain mechanisms controlling sleep and an abnormally suppressed inhibition of sensory responding in autistic children. Brainstem dysfunction has been suggested for a subgroup of autistic individuals by findings of abnormalities in brainstem ERPs, although some studies have failed to support this.
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Many ERP studies offer support for abnormalities of attention and information processing in autism. Highfunctioning autistic subjects of varying ages usually show abnormally small amplitudes for a longer latency wave of the ERP thought to reflect the detection and classification of stimuli. Deficiencies in voluntary selective attention and orientation to novel stimuli also have been shown by diminished amplitudes in waves associated with these functions. Several other neurophysiological studies relying on cerebral electrical recording have indicated disruptions in normal hemispheric lateralization in autism.
D. Neurochemical Findings Investigations of neurotransmitter function have produced inconsistent findings. The most replicated finding among autistic patients is that of elevated blood levels of the neurotransmitter serotonin, which occurs in an estimated one-third of this population, but also is observed in other patient populations. The reason for this elevation is not yet known. Treatments with the drug fenfluramine can greatly reduce levels of serotonin, and sometimes result in improvements in stereotypies and hyperactivity. Studies of the neurotransmitter dopamine are not in agreement, despite reported improvements in many symptoms after treatments with drugs that block dopamine. Overactivity of the opiate peptide beta-endorphin has been suggested by some studies, and supported by findings that opiate blockade improves autistic symptoms in some patients. The peptide oxytocin, shown to promote affiliation in animals, also may be reduced in autistic children. It has been suggested that excess opiates may render social contact unrewarding by producing a state of intrinsic contentment, and may also serve to dysregulate oxytocin.
VIII. CLINICAL ASSESSMENT
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these should be assessed by a pediatric neurologist and a pediatric OT. Some physicians believe that a full medical work-up, including EEG, genetic and chromosomal testing, CT scan, and so on, is indicated; others feel that these investigations have a low yield unless there is a specific indication for their use.
B. Neuropsychological Assessment Children and adolescents with autism or PDD should also have periodic neuropsychological evaluations. These will describe the child's current level and profile of cognitive and language abilities, which will have implications for current education and for long-range goals. Periodic reevaluations to monitor the child's progress will help to detect any deterioration that might signal negative medical or psychological events, and will document the success of treatment and education.
C. Behavioral Assessment Thorough behavioral description is equally important. Included in the behavioral description should be a profile of the individual's adaptive abilities and problem behaviors, including those central to the syndrome (such as social incapacity and resistance to change), those associated with the syndrome (such as self-injury and abnormal motor behaviors) and those sometimes found in association with it (such as hyperactivity, aggressiveness, and passivity). Analysis of antecedent conditions and consequences of the behaviors may clarify the role or function of the behavior for the particular autistic individual, and may dictate changes in stimulus conditions and reinforcements to ameliorate problem behaviors, as well as to foster positive behaviors.
IX. TREATMENT
A. Medical Assessment If the diagnosis is made by a nonphysician and the child has not yet had a medical work-up relative to his/ her autism, the following referrals should be considered. Assessment of hearing is important for successful language treatment; if behavior and cooperation are problematic, a brainstem evoked potential assessment should be done. Motor abnormalities are common;
A. Pharmacological Treatments Pharmacotherapy can be an effective tool in improving the behavior of some autistic children. Serotonergic agents are often used. Fenfluramine is sometimes prescribed, and has been found to reduce hyperactivity and stereotypies in some, but not all, studies. Clomipramine has been found to enhance social relatedness
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and decrease obsessional behavior and aggression. Fluoxetine and other serotonin reuptake inhibitors are also used with some autistic children. Opiate antagonists may help to diminish selfinjury, and reduce social withdrawal and stereotypies. Self-injury and aggression have also reported to be improved by fluoxetine, clomipramine, buspirone and beta-blockers. Neuroleptics, such as haloperidol, and chlorpromazine, have also been found to reduce agitation, aggression and emotional lability, but most physicians are reluctant to use these agents in young children because they can produce movement disorders that may not regress even when the medication is stopped. Lithium is sometimes used to decrease aggressive, perseverative, and hyperactive behavior, and may be tried especially when a family history of bipolar disorder is present. Other common pharmacological treatments are tricyclic antidepressants, which sometimes enhance language and social behavior. Stimulants have been administered for hyperactivity, but some autistic children experience a worsening of stereotypies or thought disorganization. Stimulants may work best in high-functioning autistic children with absent or mild stereotypies. Natural treatments, such as dietary interventions or high-dose vitamin regimens have been advocated by some. Empirical support for the claims rests on a small number of studies, and mainstream physicians generally do not advocate their use.
B. Behavioral and Educational Treatments Special education services and behavioral treatments are crucial in producing an optimal outcome. Recent work indicates that aggressive early intervention (as early as 15 to 18 months)can produce the best outcome. The leading proponent of intensive (ca. 40 hours/week) behavioral "drills" (O. I. Lovaas) has reported highly successful outcomes~almost half of the children being successfully included without support in a typical grade-school class. Others using his methods report results that do not replicate his degree of success, but that are nonetheless highly effective. These behavioral programs can be carried out in an educational setting or, especially for preschoolers, in the home. Other preschool programs emphasize a child-centered, developmentally oriented approach,
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which attempts to stimulate the child to move along a typical developmental trajectory. Any successful program must address each of the behavioral, social, language, and cognitive needs of the children specifically. To be effective, programs should be highly structured and should teach parents behavior management techniques that can be used in the home. Individual differences in the children partly predict outcome: higher IQ, and the presence of communicative language by the age of 5 are positive prognostic signs. The recent trend in special education has been strongly in favor of various forms of "mainstreaming, . . . . integration," and "inclusion," in which the child attends a class that is composed of a mixed group of special needs and typical peers, or of mainly typical peers, for part or all of the school day, sometimes with a one-on-one aide to facilitate participation. Although research has shown that exposure to normal peers can promote social behavior, the degree to which a severely autistic child can benefit from inclusion in a regular classroom remains to be demonstrated. It is clinically obvious that at least some autistic children need more intensive one-on-one teaching than is available in a mainstream setting before they can benefit from the teaching and social opportunities in a regular class. In addition to special education or behavioral treatment, the autistic child often needs additional speech and language therapy, occupational therapy, and adapted physical education. Clinicians must also help families to obtain other necessary services, such as respite care, extended day programs, and summer programs to prevent the behavioral and cognitive regression that can occur. They may also be able to suggest appropriate leisure activities, such as gymnastics, swimming, or play or social groups, that can provide constructive ways to spend after-school hours and opportunities for social interaction with typical children, and can promote selfesteem. Prescription of therapies and services for the autistic individual must always include sensitivity to the often devastating effect of the disability on the family. Social support from other affected families, and keeping abreast of the latest developments in treatment and other research can help families manage their affected children and their own emotional reactions. The Autism Society of America (8601 Georgia Ave.,
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Suite 503, Silver Spring, MD 20910) publishes a regular newsletter with much information useful to parents; another good source of information for parents and professionals on recent developments in autism is Rimland's newsletter Autism Research Review International (4182 Adams Ave., San Diego, CA 92116).
BIBLIOGRAPHY Bauman, M. L., & Kemper, T. L. (Eds.). (1994). The neurobiology of autism. Baltimore: The Johns Hopkins University Press.
Dawson, G. (Ed.). (1989). Autism: Nature, diagnosis and treatment. New York: Guilford Press. Gillberg, C., & Coleman, M. (1992). The biology of the autistic syndromes (2nd ed.). Clinics in Developmental Medicine, 126. London: Mac Keith Press. Rapin, I. (Ed.). (1996). Preschool children with inadequate communication: Developmental language disorder, autism, low IQ. Clinics in Developmental Medicine, 139. London: Mac Keith Press. Schopler, E., & Mesibov, G. (Eds.). (1995). Learning and cognition in autism. New York: Plenum Press. Schopler, E., Van-Bourgondien, M. E., & Bristol, M. (Eds.). (1993). Preschool issues in autism. New York: Plenum Press.
Autism and Pervasive Developmental Disorders
I. II. III. IV. V. VI. VII. VIII. IX.
Deborah Fein and LeeAnne Green
Lynn Waterhouse
University of Connecticut
The College of New Jersey
Historical Development of the Concept of Autism DSM-IV Criteria Behavioral and Cognitive Characteristics Developmental Course and Prognosis Epidemiology Boundary Conditions and Comorbidity Biological Factors Clinical Assessment Treatment
PERVASIVE DEVELOPMENTAL DISORDERS (PDD) is the current term for what is probably a group of related neurodevelopmental disorders characterized by similar behavioral profiles. Autistic Disorder is the most widely studied and best described of these disorders. It is characterized by deficits in social relatedness, deficits in language and communication, and stereotyped and restricted patterns of behavior, and is frequently but not always accompanied by mental retardation.
Echolalia Parrot-like repetition of utterances either immediately after hearing the utterance (immediate echolalia) or at a later time (delayed echolalia). Gaze Avoidance The tendency to avert one's eyes in order to avoid eye-to-eye contact with another. Mainstreaming The integration, or partial integration, of a child with special needs into a classroom of typically developing children. Metaphorical Language Idiosyncratic utterances whose meaning is clear only to those who are familiar with the child's history. Pragmatics The social aspects of language, or the communicative uses to which language is put. Stereotypies Repetitive and often unusual motor movements. Stimulus Overselectivity A tendency to attend to a restricted portion of a stimulus array or a complex stimulus. Theory of Mind An understanding or concept of the existence of mental representations, including knowledge and perspective, in others.
I. HISTORICAL DEVELOPMENT OF THE CONCEPT OF AUTISM Autism was first described by Leo Kanner in 1943 and became known as Infantile Autism or Autistic Disorder. The concept has expanded since that date, and the term "Kanner autism" is sometimes used to refer to cases with symptoms similar to those of Kanner's original sample; such cases are a subset of PDD. Kanner's original description remains influential, and there is a tendency in the literature to assume that persons with "Kanner autism" represent the "nuclear" or "core" form of PDD, an assumption that may not be warranted. Kanner identified symptoms in three main groups: an autistic aloneness, a failure to use language communicatively, and an obsessive insistence on sameness in the environment; these are still the three areas of symptomatology used in current diagnostic systems. Although Kanner originally viewed the autis-
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tic aloneness as probably representing a constitutional defect, the two decades following his original work were marked by an unfortunate shift toward a psychodynamic/environmental view of the causation of autism. This served to derail any significant progress in understanding the disorder, as well as to cause a great deal of additional anguish to parents of autistic children. Beginning with Rimland's seminal work on autism in 1964, psychology and psychiatry began to explore seriously the biological foundations of autism, and theories of autism as resulting from disturbances in attention, language, sensory integration, perceptual constancy, and other neurological functions were promulgated and tested. Beginning in the early to mid1980s, research attention also began to focus seriously on the social and affective aspects of autism, both to clarify the range of heterogeneity in autistic children's functioning, and to posit new core deficits in these areas. Currently, researchers stressing both cognitive and social/affective deficits as primary are in agreement that the fundamental problem is a neurological, and not an environmental, one. Differential diagnosis was a conceptual problem for early autism research. Some clinicians believed that autism was a variant of or precursor to schizophrenia. Only in the 1970s came an awareness that disorders beginning in infancy must be regarded as separate in kind from those with onset in later childhood, adolescence, or adulthood. Autistic-like disorders virtually always begin before age 3, while schizophrenic-like disorders virtually never begin before age 7. This realization revitalized interest in infantile autism as a distinct nosologic entity, leading to the development of more operationally precise diagnostic criteria and a reconceptualization of the syndrome as a pervasive developmental disorder, under which label it was incorporated by the American Psychiatric Association in the third edition of that body's Diagnostic and Statistical Manual of Mental Disorders (DSM-III ); this conceptualization has been retained in DSM-III-R and DSM-
IV. [See SCHIZOPHRENIA.]
II. DSM-IV CRITERIA Current diagnostic practice, as reflected in the DSMIV, classifies Autistic Disorder as one of four specific
entities within Pervasive Developmental Disorder. Autistic Disorder is marked by the presence of symptomatology in three areas: (1) qualitative impairment in social interaction, as manifested by such behaviors as abnormal or reduced eye contact with others, failure to develop peer relationships, lack of spontaneous sharing of interests with others (e.g., showing or pointing out objects of interest to the caregiver), (2) qualitative impairment in communication, as manifested by delayed or deviant language without attempts to compensate through nonverbal communication, poor conversational skills if speech is present, and repetitive and stereotyped language and play, and (3) a restricted and repetitive repertoire of behaviors and interests, including preoccupations and rituals, or severe resistance to environmental changes. The specific behavioral manifestations of these traits differ by degree of accompanying retardation and age. A high-functioning, older autistic individual, for example, may attempt to be social, but violate implicit rules of social behavior and be insensitive to unspoken social signals, while a low-functioning or much younger autistic individual may react to other people as if they were little different from inanimate objects. Similarly, a high-functioning, older autistic individual may have perseverative interests in such topics as constellations, train schedules, or dinosaurs, and attempt to engage others in conversations on these subjects, while a lower functioning or younger autistic individual might engage in repetitive motor rituals. The other specific syndromes classified as Pervasive Developmental Disorders include Rett's Disorder, Asperger's Disorder, and Childhood Disintegrative Disorder. Rett's Disorder has marked behavioral commonalities with Autistic Disorder, including poor social engagement and mental retardation, but differs from Autistic Disorder in several ways: in Rett's Disorder, the retardation is more invariant and more typically severe, the disorder seems to present only in girls, it is marked by a characteristic pattern of head growth deceleration and loss of purposeful hand movements, sometimes accompanied by hand wringing behavior, following a period of normal development. Many girls with Rett syndrome also have epilepsy and other neurologic abnormalities. Asperger's Disorder is often considered a mild form of Autistic Disorder, and there is still controversy about how distinct it is from autism;
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diagnostically, it can be distinguished from autism by normal development of language. Childhood Disintegrative Disorder differs from Autistic Disorder in that the former is marked by a distinctive pattern of developmental regression following at least two years of normal development. This disorder is much rarer than autism, and controversy exists here, too, about the etiological and phenomenological distinctiveness between Childhood Disintegrative Disorder and Autistic Disorder. [See MENTAL RETARDATION AND MENTAL HEALTH.]
III. BEHAVIORAL AND COGNITIVE CHARACTERISTICS A. Behavioral Characteristics in Autism I. Social Behavior Social behavior is considered by many as the hallmark of autism. As with all features of autism, social impairment is highly heterogeneous; it varies with age, with IQ, with setting, and with interactive partner, and is modifiable by treatment. Social impairment is generally most severe in the preschool years; it is in early childhood that genuine aloofness is seen. Older children may initiate interaction to get their needs met, or may be responsive but noninitiating to others. Older or higher-functioning autistic individuals may approach others in an idiosyncratic, intrusive, and socially insensitive way. These three general styles (aloof, passive, active-but-odd) form the basis of a social typology described by Lorna Wing, and validated by several later studies. Highly structured settings with enforced proximity to peers may elicit the best peer interactions. Relationships with other children are almost always more impaired than the corresponding behavior with adults; other children may be ignored when adults are not. Behavioral deficits in social interaction are varied; among the most important, especially in early life, are (1) poor spontaneous imitation of others' language and behavior, (2) gaze avoidance or other deficits in the use of eye-to-eye gaze to modulate or initiate interaction, and (3) deficits in various joint attention skills, including drawing an adult's attention to an object of interest by showing or pointing, and following an adult's attentional focus in order to share it. On the
other hand, the "pervasive lack of responsiveness" described in DSM-III is actually uncommon; many young autistic children are selectively attached to their parents, derive comfort from their presence, and enjoy physical affection.
2. Communication and Play Older studies were composed primarily of clinical descriptions of language features such as pronoun reversal, echolalia, and metaphorical language. More systematic studies have appeared, based on modern understanding of the separable components of language. The more severely affected autistic child may remain nonverbal or minimally verbal and poorly intelligible. In those who develop more language, phonology, syntax, and (more arguably) semantics are relatively spared, although still often at a lower level than nonverbal skills. Verbal memory, prosody, and pragmatics, on the other hand, represent areas of particular difficulty for the average autistic child. In the domain of pragmatics, it is noted that communicative functions are generally more need-oriented and less affiliative, and that violations of language use rules are common, such as violations of implicit rules concerning interpersonal distance while speaking, and the rules of turn-taking in conversational exchange, as well as word selection which is overly formal or pedantic. Symbolic play is also often observed to be lacking in young autistic children, who sometimes prefer nonsymbolic play activities such as puzzles or other manipulatives. When symbolic play develops, it can be unusually repetitive and inflexible in nature. Some recent evidence suggests that high-functioning autistic children may be not so much incapable as uninterested in engaging in frequent or complex symbolic play.
3. Preoccupations, Perseverations, and Resistance to Change These constitute the third symptom group. These behaviors range from simple or complex motor stereotypies, to "self-stimulatory" sensory behaviors such as watching fans or water, to long-term perseverative interests. The resistance to change is manifested by tantrums or other extreme reactions to changes in environmental features or in routines. Despite the equal role assigned to perseverations/preoccupations and resistance to change in diagnostic criteria, some
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recent data suggest that resistance to change is a less common feature of autism than perseverations/preoccupations.
B. Cognitive Characteristics Overall cognitive level, or presence of mental retardation, is an important feature of the individual autistic child, and powerfully predicts the functional outcome that can be expected for the child. Recent work by several research groups, such as the group headed by Rapin (see Bibliography) suggests that high- and low-functioning autism may be significantly different in behavioral manifestations, history, and prognosis, that approximately half of the autistic population falls into each group, and that an IQ cutoff of about 65 makes the most appropriate division between highand low-functioning autism. Beyond studies of overall cognitive level, many investigators have examined typical cognitive profiles in autism, that is, areas of relative sparing and impairment. Some autistic children, both those with severe impairment and those who are higher functioning, display unusual gifts, especially in rote memory, calculations, and music. A majority of autistic children are known to have relative strengths in visuospatial abilities, while tasks requiring verbal reasoning, social cognition, or flexibility pose relative difficulty for the autistic child. Although this description suggests a typical cognitive profile, studies have shown that there is great heterogeneity in the autistic population, and that no single cognitive deficit is universal in autistic individuals.
I. Language The autistic child's language profile is arguably the syndrome's most distinctive cognitive feature, which has earned it a central position in some theories of the etiology of autism. Many aspects of verbal functioning are impaired in autistic children, as many as 40 to 50% of whom are mute, although this figure is declining with the advent of aggressive early intervention. Those with speech often display echolalia, difficulties with prepositions and pronouns, and inappropriate conversational behaviors. Verbal autistic children generally are able to acquire normal grammatical morphology and syntax, although onset and development are delayed. Some autistic children learn
grapheme-phoneme correspondence, leading to early decoding of words; comprehension, however, lags far behind. Comprehension of oral language is significantly impaired relative to expression, and deficits in the semantic and pragmatic aspects of language are common. They are also deficient in interactive communication, including conversational behavior, nonverbal communication and speech prosody. In general, the more linguistic aspects of communication, including especially phonology and syntax, are spared relative to the pragmatic aspects; pragmatic deficits can be seen in the failure to use language functionally to share or request information, or perform other speech functions that serve social, rather than instrumental, functions.
2. Social Cognition A decade of research has documented substantial deficits in autistic children's ability to understand the behavior, emotions, and cognitive states of other people. They have difficulty in matching pictures of emotional facial expressions to emotion words, to emotional situations, to similar expressions, and to vocal expressions of the same emotion. Much recent interest has been stimulated by exploration of autistic performance on "theory of mind" tasks; in a typical theory of mind task, the subject is asked to predict behavior of a doll in a social scenario. The behavior can only be correctly predicted if the subject has a true theory of mind, that is, truly understands the concept of others' minds, with their own representational capacities, and their own limits on available knowledge. Autistic subjects have been shown to be impaired on these tasks in several studies. A cautionary note here, however, about all of these social cognitive tasks is that many higher functioning autistic individuals do well on them; the deficits are far from universal. Furthermore, verbal IQ explains much of the variance in performance. Therefore, it remains to be demonstrated that deficits in social cognition, including theory of mind, occupy a key causal role in the syndrome; they may be more a concomitant deficit related to the overall social impairment, although opinions differ widely on this.
3. Attention Unusual attentional processes are characteristic of autistic children. Autistic children are generally able to
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sustain attention in tasks adequately when given potent reinforcement or when the task is of interest to them, and higher functioning individuals are able to perform well on standard neuropsychological tests of sustained attention. In contrast, many autistic children appear to have difficulty with tasks requiring the focusing and shifting of attention. They are found to be overseiective in their attention to particular parts of stimuli, and studies indicate that they may have difficulties in shifting attention between stimuli, especially across sensory modalities, perhaps contributing to the perseveration so characteristic of their behavior.
4. Memory Memory abilities in autism have not been as fully investigated as other cognitive functions. Anecdotally, amazing feats of memory have been reported, where autistic individuals recall distant episodes with great clarity and detail; hyperdeveloped memory for stimuli such as routes, spatial arrays, schedules and calendars, and music have also been frequently reported. Tested memory for visual material in high-functioning autistic individuals is often normal. In contrast, memory for linguistic and social material is usually impaired. Autistic individuals appear not to be able to use the intrinsic semantic structure of discourse or stories to aid recall, and in this regard, are more impaired than children with specific language disorders.
5. Executive Functions Executive functioning refers to the higher level cognitive processes of abstract conceptualization, planning, problem solving, and self-monitoring, self-correction and self-control. These processes are thought to be localized to prefrontal cortex, and are assessed with standardized neuropsychological tests developed for evaluation of frontal functions. Some autistic individuals have great difficulty with these tasks, especially in switching from incorrect strategies during tasks. Some researchers have noted similarities between certain symptoms of autism and those of patients with frontal lobe damage (e.g., perseveration, lack of inhibition), and have proposed that frontal executive system impairment causes distinct social cognitive deficits. Furthermore, some findings suggest that executive system adequacy may predict outcome for autistic adolescents better than measures of IQ.
IV. DEVELOPMENTAL COURSE AND PROGNOSIS Autism, as a developmental disorder, cannot be fully described at a single developmental point. The typical description of the autistic child is that he or she lacks interest in relating to others and lacks communicative language. These symptoms are most characteristic of autistic children in the preschool years. Even during this period, there are often signs of increasing social relatedness, especially to caretakers. On the other hand, stereotypies and especially resistance to change, may appear in the preschool years or somewhat later. During middle childhood, autistic children often master some daily living and academic skills and make behavioral adjustments to their parents and teachers. Their behavior may come to resemble that of hyperactive and/or retarded children, or they may develop into socially motivated children, who relate in an odd or idiosyncratic way, with deficits in emotional reciprocity. Early and middle adolescence can be particularly difficult. Besides the onset of seizures that sometimes occurs in early adolescence, a significant minority of PDD children regress behaviorally and even cognitively at this time. Some autistic adolescents show increasing interest in developing peer relationships during these years. Higher functioning individuals with PDD are prone to psychiatric problems, especially anxiety and depression, as they realize the extent of their difference from peers. On the positive side, both social and language skills often continue to improve during adolescence, and even those children who regress during early adolescence may recover and make developmental progress toward the middle or end of adolescence. Increasing interest in relating to other people can also set the stage for psychosocial interventions or behavioral skill training to be more effective. Long-term follow-up studies indicate great variability in adult outcomes, but a generally guarded prognosis for good adjustment must be the rule. About half of all autistic adults require residential care; many of the remainder depend on relatives for daily assistance. Gainful employment and fully independent living may be achieved by about one in five. Even for the best-outcome group, social difficulties remain common, marriage or sexual relationships rare, and many social relationships revolve around work or struc-
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tured activities and interests. It should be noted, however, that the generation of children who have received the benefit of modern special education and behavioral interventions have not yet reached adulthood, and their outcomes, it is hoped, will be significantly better. Follow-up studies are consistent in demonstrating that higher IQ and communicative language by the age of 5 are strong predictors of better outcome, associated neurological signs and symptoms are predictors of poorer outcome.
V. EPIDEMIOLOGY Prevalence rates vary according to the definition of the syndrome. Earlier and more restrictive definitions of autism yielded prevalence estimates of 2-4/10,000. Broader definitions encompassing the full PDD spectrum suggested rates three or more times greater. Recent estimates have increased. This may be attributable to improved detection, more lenient diagnoses, or actual increases in prevalence. Most recent estimates are approximately 10/10,000 for PDD disorder, including autism, and another 10/10,000 with a more broadly defined triad of deficits in social relatedness, communication, and stereotyped behavior plus mental retardation. PDD spectrum disorders are more common in males than in females, with ratios found between 2:1 and 10:1, the higher ratios applying more to the Asperger-type clinical picture.
VI. BOUNDARYCONDITIONS AND COMORBIDITY Specifying the boundary between autism and other PDD spectrum disorder (such as Rett's and Asperger's Disorder), mixed language disorder, or severe mental retardation can be problematic, and differential diagnoses among these conditions can be difficult. Although diagnostic definitions of autism and language disorder appear distinct, in practice, the differential diagnosis can be unclear, especially in preschool children. Studies from Rutter and colleagues in the 1970's and from Rapin's group indicate that the diagnostic groups can be distinguished not only by the presence of autism-related behaviors, but by differences in the
language domain itself. The autistic children tend to have greater delays and deficits in language comprehension than the language-disordered children; in the expressive domain, delayed appearance of Wh-questions is highly discriminating. Regression of acquired language skills is also much more typical of autism, but also characterizes children with Landau-Kleffner syndrome. Landau-Kleffner syndrome, also referred to as acquired epileptic aphasia, refers to loss of language in a child in the context of clinical seizures or a frankly epileptiform EEG. There is disagreement as to whether the term should be reserved for children who have no serious associated behavior or cognitive disorders, or whether the term should be broadened so as to include those children who also develop autistic behaviors or become frankly autistic. Autism may also have increased comorbidity with specific additional disorders. Although still controversial, some investigators present evidence that there is a greater than chance coincidence of autism and Tourette's disorder. When tics occur in autism, they tend to occur in high-functioning autism. The relationship between autism and schizophrenia also remains a matter of debate. At one time, the two disorders were believed to be related, but different ages of onset, patterns of symptomatology, and family histories have convinced many investigators that they are unrelated. Nevertheless, reports exist of schizophrenia developing in previously autistic individuals at a greater than chance rate, and a small number of researchers believe that autism is a particularly early and severe form of childhood schizophrenia. Autism is also related to the presence of seizure disorders. About half of autistic individuals have clinical seizures and/or abnormal EEGs. Infancy and adolescence are high-risk periods for the appearance of seizures. All types of seizures occur; generalized tonicclonic are the most common.
VII. BIOLOGICAL FACTORS A. Associated Biomedical Conditions and Genetic Factors Several specific medical conditions are associated with autism, including phenylketonuria, rubella embryopathy, herpes encephalitis, fragile X syndrome, and neurocutaneous disorders such as tuberous sclerosis.
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Some studies estimate that between one-eighth and one-fourth of autistic children have an associated medical condition, but it is not known whether these conditions play a causal role in the development of autistic symptoms. Of possible prenatal factors, maternal rubella is most commonly associated with autism, the prevalence for which is 100 times that for the general population. Other obstetrical factors are found more frequently in autistic children than in other populations, particularly midpregnancy maternal bleeding. The fragile X genetic syndrome has been identified in an estimated 2 to 10% of the autistic population. Fragile X is a rare X-linked syndrome (most prevalent in boys) that involves intellectual impairment, attention deficits, and identifying physical features (prominent ears, long and narrow face, and macroorchidism). Within the fragile X population, it is estimated that 15 to 30% have autistic features, which are qualitatively distinct compared with those seen in the "typical" autistic child. Fragile X autistic children have been found to show perseverative speech as opposed to echolalia, and display active-but-odd social behaviors rather than aloofness. The specific route of pathology connecting fragile X to the expression of autistic symptoms is unknown. A genetic basis for at least some forms of autism has been demonstrated by family studies. Approximately 3 % of families with an autistic child will produce another child with autism, a prevalence rate which equals 50 to 100 times that of the general population. In addition, the concordance rate for autism in monozygotic twins has been found to range from 40 to 96%. Further support for genetic involvement is found in studies of characteristics in families of autistic children. Siblings of autistic children may be more likely to show superiority in visuospatial over verbal abilities (analogous to the autistic profile), cognitive difficulties such as language disorder, and social disengagement. A few studies have found that some parents of autistic children may be more likely to show unusual social behaviors. The search for specific genetic markers for autism thus far has uncovered two prospects: a marker for a gene that regulates neuron development, and abnormalities of chromosome 15. Taken together, studies suggest that at least a subset of autistic cases are attributable to genetic origin, either familial or mutational. The incidence of autistic
symptoms in medical conditions that are not genetic, however, suggests that the PDD spectrum may represent a variety of etiologies ultimately affecting common brain systems.
B. Neuroanatomical Findings Studies of neuroanatomical abnormalities in autistic patients have relied mainly upon postmortem neuropathology examinations and imaging techniques such as positron emission tomography (PET), computerized tomography (CT) and magnetic resonance imaging (MRI). They have generally focused on cortex, brainstem, limbic areas and cerebellum, and have found great variability in brain pathology. Gross cortical and ventricular abnormalities, for example, have been found in some cases and not others. Two structures of great interest are the amygdala and hippocampus, which are limbic structures involved in social/emotional behaviors and in memory. Abnormalities in limbic areas of the brain have been implicated in several studies, most notably in detailed postmortem examinations performed by Bauman and Kemper. These and other studies have also found abnormalities in the cerebellum, although the nature of these cerebellar abnormalities is not consistent across studies.
C. Neurophysiological Findings Findings from PET studies of regional cerebral blood flow have suggested diminished temporal lobe activity, and possible delayed frontal lobe maturation in autistic children. PET studies of regional glucose metabolism, which reflects brain energy utilization, have indicated abnormal patterns of regional activation. Several others have found global glucose hypermetabolism in autistic patients, which was thought to reflect inefficient processing. This feature, however, is not unique to autism. Studies examining brain waves and oculomotor activity in REM sleep have suggested a developmental immaturity of brain mechanisms controlling sleep and an abnormally suppressed inhibition of sensory responding in autistic children. Brainstem dysfunction has been suggested for a subgroup of autistic individuals by findings of abnormalities in brainstem ERPs, although some studies have failed to support this.
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Many ERP studies offer support for abnormalities of attention and information processing in autism. Highfunctioning autistic subjects of varying ages usually show abnormally small amplitudes for a longer latency wave of the ERP thought to reflect the detection and classification of stimuli. Deficiencies in voluntary selective attention and orientation to novel stimuli also have been shown by diminished amplitudes in waves associated with these functions. Several other neurophysiological studies relying on cerebral electrical recording have indicated disruptions in normal hemispheric lateralization in autism.
D. Neurochemical Findings Investigations of neurotransmitter function have produced inconsistent findings. The most replicated finding among autistic patients is that of elevated blood levels of the neurotransmitter serotonin, which occurs in an estimated one-third of this population, but also is observed in other patient populations. The reason for this elevation is not yet known. Treatments with the drug fenfluramine can greatly reduce levels of serotonin, and sometimes result in improvements in stereotypies and hyperactivity. Studies of the neurotransmitter dopamine are not in agreement, despite reported improvements in many symptoms after treatments with drugs that block dopamine. Overactivity of the opiate peptide beta-endorphin has been suggested by some studies, and supported by findings that opiate blockade improves autistic symptoms in some patients. The peptide oxytocin, shown to promote affiliation in animals, also may be reduced in autistic children. It has been suggested that excess opiates may render social contact unrewarding by producing a state of intrinsic contentment, and may also serve to dysregulate oxytocin.
VIII. CLINICAL ASSESSMENT
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these should be assessed by a pediatric neurologist and a pediatric OT. Some physicians believe that a full medical work-up, including EEG, genetic and chromosomal testing, CT scan, and so on, is indicated; others feel that these investigations have a low yield unless there is a specific indication for their use.
B. Neuropsychological Assessment Children and adolescents with autism or PDD should also have periodic neuropsychological evaluations. These will describe the child's current level and profile of cognitive and language abilities, which will have implications for current education and for long-range goals. Periodic reevaluations to monitor the child's progress will help to detect any deterioration that might signal negative medical or psychological events, and will document the success of treatment and education.
C. Behavioral Assessment Thorough behavioral description is equally important. Included in the behavioral description should be a profile of the individual's adaptive abilities and problem behaviors, including those central to the syndrome (such as social incapacity and resistance to change), those associated with the syndrome (such as self-injury and abnormal motor behaviors) and those sometimes found in association with it (such as hyperactivity, aggressiveness, and passivity). Analysis of antecedent conditions and consequences of the behaviors may clarify the role or function of the behavior for the particular autistic individual, and may dictate changes in stimulus conditions and reinforcements to ameliorate problem behaviors, as well as to foster positive behaviors.
IX. TREATMENT
A. Medical Assessment If the diagnosis is made by a nonphysician and the child has not yet had a medical work-up relative to his/ her autism, the following referrals should be considered. Assessment of hearing is important for successful language treatment; if behavior and cooperation are problematic, a brainstem evoked potential assessment should be done. Motor abnormalities are common;
A. Pharmacological Treatments Pharmacotherapy can be an effective tool in improving the behavior of some autistic children. Serotonergic agents are often used. Fenfluramine is sometimes prescribed, and has been found to reduce hyperactivity and stereotypies in some, but not all, studies. Clomipramine has been found to enhance social relatedness
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and decrease obsessional behavior and aggression. Fluoxetine and other serotonin reuptake inhibitors are also used with some autistic children. Opiate antagonists may help to diminish selfinjury, and reduce social withdrawal and stereotypies. Self-injury and aggression have also reported to be improved by fluoxetine, clomipramine, buspirone and beta-blockers. Neuroleptics, such as haloperidol, and chlorpromazine, have also been found to reduce agitation, aggression and emotional lability, but most physicians are reluctant to use these agents in young children because they can produce movement disorders that may not regress even when the medication is stopped. Lithium is sometimes used to decrease aggressive, perseverative, and hyperactive behavior, and may be tried especially when a family history of bipolar disorder is present. Other common pharmacological treatments are tricyclic antidepressants, which sometimes enhance language and social behavior. Stimulants have been administered for hyperactivity, but some autistic children experience a worsening of stereotypies or thought disorganization. Stimulants may work best in high-functioning autistic children with absent or mild stereotypies. Natural treatments, such as dietary interventions or high-dose vitamin regimens have been advocated by some. Empirical support for the claims rests on a small number of studies, and mainstream physicians generally do not advocate their use.
B. Behavioral and Educational Treatments Special education services and behavioral treatments are crucial in producing an optimal outcome. Recent work indicates that aggressive early intervention (as early as 15 to 18 months)can produce the best outcome. The leading proponent of intensive (ca. 40 hours/week) behavioral "drills" (O. I. Lovaas) has reported highly successful outcomes~almost half of the children being successfully included without support in a typical grade-school class. Others using his methods report results that do not replicate his degree of success, but that are nonetheless highly effective. These behavioral programs can be carried out in an educational setting or, especially for preschoolers, in the home. Other preschool programs emphasize a child-centered, developmentally oriented approach,
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which attempts to stimulate the child to move along a typical developmental trajectory. Any successful program must address each of the behavioral, social, language, and cognitive needs of the children specifically. To be effective, programs should be highly structured and should teach parents behavior management techniques that can be used in the home. Individual differences in the children partly predict outcome: higher IQ, and the presence of communicative language by the age of 5 are positive prognostic signs. The recent trend in special education has been strongly in favor of various forms of "mainstreaming, . . . . integration," and "inclusion," in which the child attends a class that is composed of a mixed group of special needs and typical peers, or of mainly typical peers, for part or all of the school day, sometimes with a one-on-one aide to facilitate participation. Although research has shown that exposure to normal peers can promote social behavior, the degree to which a severely autistic child can benefit from inclusion in a regular classroom remains to be demonstrated. It is clinically obvious that at least some autistic children need more intensive one-on-one teaching than is available in a mainstream setting before they can benefit from the teaching and social opportunities in a regular class. In addition to special education or behavioral treatment, the autistic child often needs additional speech and language therapy, occupational therapy, and adapted physical education. Clinicians must also help families to obtain other necessary services, such as respite care, extended day programs, and summer programs to prevent the behavioral and cognitive regression that can occur. They may also be able to suggest appropriate leisure activities, such as gymnastics, swimming, or play or social groups, that can provide constructive ways to spend after-school hours and opportunities for social interaction with typical children, and can promote selfesteem. Prescription of therapies and services for the autistic individual must always include sensitivity to the often devastating effect of the disability on the family. Social support from other affected families, and keeping abreast of the latest developments in treatment and other research can help families manage their affected children and their own emotional reactions. The Autism Society of America (8601 Georgia Ave.,
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Suite 503, Silver Spring, MD 20910) publishes a regular newsletter with much information useful to parents; another good source of information for parents and professionals on recent developments in autism is Rimland's newsletter Autism Research Review International (4182 Adams Ave., San Diego, CA 92116).
BIBLIOGRAPHY Bauman, M. L., & Kemper, T. L. (Eds.). (1994). The neurobiology of autism. Baltimore: The Johns Hopkins University Press.
Dawson, G. (Ed.). (1989). Autism: Nature, diagnosis and treatment. New York: Guilford Press. Gillberg, C., & Coleman, M. (1992). The biology of the autistic syndromes (2nd ed.). Clinics in Developmental Medicine, 126. London: Mac Keith Press. Rapin, I. (Ed.). (1996). Preschool children with inadequate communication: Developmental language disorder, autism, low IQ. Clinics in Developmental Medicine, 139. London: Mac Keith Press. Schopler, E., & Mesibov, G. (Eds.). (1995). Learning and cognition in autism. New York: Plenum Press. Schopler, E., Van-Bourgondien, M. E., & Bristol, M. (Eds.). (1993). Preschool issues in autism. New York: Plenum Press.