The World of Autism.

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Autism Menu
Introduction
Primary Characteristics
Associated Feature
Differential Diagnosis
Demography & Epidemiology
Etiology
Neurological Correlates
Theories of Autism
Treatment

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Autism is the most severe of the developmental disabilities with an incidence of approximately 1 per 1000 live births. Originally thought of as an emotional disorder caused by inadequate mothering, it is now recognised as having an organic basis. The primary problem in autism is the way the brain processes and integrates information, resulting in problems of social interaction, communication and behaviour. Several causes have been identified and a variety of neurological mechanisms are involved. Although autism is a severely handicapping condition, outcomes for autistic people are improving as more effective interventions and more appropriate community resources are developed, most autistic people have a normal life span, if they are to achieve their potential there is a compelling need for more community- based, cost effective resources.

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Primary characteristics

The primary characteristics of autism include impaired reciprocal social interactions, impaired communication, and restricted behaviours. The impaired social interactions are among the most conspicuous of the autistic deficits and were the reason leo kanner used the term "autism" to describe the syndrome in 1943. Social difficulties of autism include impaired social play, a general preference for isolation in the presence of others, failure to seek comfort at times of distress, indifference to others and an inability to understand social rules and conventions.

Communication and language problems are also primary in autism. Approximately 50% of autistic people do not develop meaningful communicative language and most autistic people also have problems with other forms of communication. Verbal autistic youngsters are frequently echolalic and cannot engage in social conversations. Non-verbal youngsters have difficulty understanding or being understood and consequently often retreat from interactions with others. Play is impaired in most autistic youngsters, lacking the social and creative aspects generally seen in non-handicapped children.

The third primary characteristic of those with autism is their restricted range of behaviours, activities and interests. Lower functioning autistic people frequently engage in repetitive bodily movements, self stimulatory behaviours and sometimes even self abuse. Their play patterns are restricted and repetitive. Higher level autistic people may focus on some topics that are narrow and generally uninteresting to others: bus schedules, airplane timetables, geography, or numbers.

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Associated features

In addition to the primary characteristics that define the autism syndrome, there are associated features that are frequently present as well. Although these features are not essential for a diagnosis of autism, they are often observed in this group and can have important implications for the treatment of autistic children: abnormalities in the development of cognitive skills, abnormalities of posture and motor behaviour, unusual sensory responses, abnormalities in eating, drinking or sleeping, abnormalities of mood, and self-injurious behaviours.

Several cognitive abnormalities are frequently observed in autistic youngsters: distractibility, poor organisational ability, difficulties with abstractions and a strong focus on details. Mental retardation is an additional cognitive disability in about 70% of autistic people and there is often an uneven cognitive profile with some skills being strong while other aspects of cognitive functioning are quite limited.

Abnormalities of posture and motor behaviour include stereotypes like arm flapping and grimacing, abnormal gaits, and odd posturing with the hands. Under and over-responsivity to sensory input are common; some autistic people resist being touched while others ignore sensations like pain. Many autistic people are fascinated by specific sounds or tastes.

Abnormalities of drinking, eating, and sleeping behaviour and fluctuations of mood are also frequently observed. Eating, drinking and sleeping problems often resolve themselves by adolescence but can be troublesome prior to then. Eating a limited variety of foods and staying up all night are among the most difficult of the ongoing problems parents face with autistic youngsters. A liability to changes of mood is also common and is observed in several variations: giggling or weeping for no apparent reason, absence of emotional responses or reactions to danger, excessive fearfulness, or generalized anxiety.

Self-injurious behaviours, such as head banging and finger or hand biting, are the most extreme and frightening of the behaviours accompanying autism. These occur in less than 10% of the population but can be the most difficult to control or to suggest a remedy for. In their most extreme form these behaviours require treatment in hospital.

Although age of onset is no longer a diagnostic criteria, autism begins early in life (almost always before age 3 and rarely after age 5). Most autistic children show signs of deterioration of social, cognitive, behavioural and communicative skills. In these instances deterioration following normal language development is usually the first indication of a problem.

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Differential diagnosis

One of the most troubling aspects of having a child with autism is the confusion among professionals concerning diagnostic issues. Diagnosing autism can be difficult because it resembles other disabilities of behaviour, communication and learning. Because autism is also a rare disorder, most professionals do not see enough cases for them to consistently identify subtle distinctions between this syndrome and related disabilities. The historical confusion between autism and emotional difficulties has further clouded the diagnostic picture. Over a period of time, autism has been mis-diagnosed as many different disabilities: mental retardation, schizophrenia, development language problem, hearing impairment, or pervasive developmental disorder, not otherwise specified.

The relationship between autism and mental retardation has been a source of confusion for several decades. Many have noted the intellectual impairments in people with autism that resemble the limitations of mentally retarded people. Compared with mentally retarded people, however, individuals with autism have more intellectual strengths - which can even be above average in some areas - and a wider spread between their skills and deficits. Gross motor skills of autistic children also tend to be stronger. Mentally retarded children, on the other hand, generally have better social and communication skills in relation to their overall developmental levels. A major source of the confusion between these two disabilities has been the historical notion that autism is a relatively "pure" disability that cannot co-exist with other syndromes like mental retardation.

The relationship between autism and mental retardation has been clarified more recently with the acknowledgement that autism, as a behavioural syndrome, can and does co-exist with other disabilities. The most common of these co-occuring disabilities is mental retardation. Current estimates are that approximately 70% of individuals with autism have an additional diagnosis of mental retardation.

In identifying autism, leo kanner described it as the earliest form of childhood schizophrenia because of the similarities he observed between the conditions. Today, autism and schizophrenia are seen as distinct and different; autism is viewed as a developmental disorder and schizophrenia is classified as a mental illness. The other major differences are the hallucinations and delusions in schizophrenia, absent in autism, and the earlier onset of autism (almost always before age 5), the onset of schizophrenia is most frequently during adolescence.

Investigators have recently identified other important distinctions between autism and schizophrenia. The family histories of children in these diagnostic groups are generally different; children with autism have stronger family histories of developmental disabilities and families of schizophrenics have stronger histories of personality, affective, and other emotional disorders. Autistic children are physically healthier and have better motor skills on the average. While autistic children never form appropriate interpersonal relationships, schizophrenia is viewed as a withdrawal from presumably unsatisfactory relationships, often because of a particular traumatic event. Finally, schizophrenics generally have higher iqs that children with autism and they also have periods of remisions when their behaviour returns to near normal.

Language and hearing impairments can also be confused with autism. Language impairments in children with autism include delayed development of vocal expression and language comprehension, echolalia, pronoun reversals and problems with sequencing. These communication difficulties can occur and sometimes limit the social relationships of children with language impairments, though not nearly as much as in children with autism. Compared with autistic children, those with communication handicaps use alternative forms of communication more effectively (e.g. Gestures), have higher iqs, engage in more imaginative play and have a better prognosis.

Non-responsive and indifferent to others, children with autism can also be mis-diagnosed as hearing impaired. Recent advances in testing have reduced the frequency of this problem; audiologists have now better ways of testing non-verbal children. There is also a growing awareness that non-responsiveness does not mean that a child cannot hear. Other differences between hearing impaired and autistic children include higher iqs, better relationships, better non-verbal communication, and a better prognosis for children with hearing impairments.

A recent source of diagnostic confusion has been the introduction of pervasive developmental disorder, not otherwise specified (pddnos) into the current diagnostic system, dsm-111-r. Within this scheme, autism is classified as a pervasive developmental disorder (pdd); pddnos is the only other subclassification under pdd. According to dsm-111-r, pddnos is designed to classify those children with characteristics of autism but not the full syndrome. Unfortunately, a lack of precision has made it unclear exactly what these pddnos children should look like. Designed to clarify the boundaries of autism, pddnos has added more confusion than illumination.

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Demography and epidemiology

the prevalence of autism is generally estimated as 1 case per 1000 population. About 70% of those diagnosed as autistic function intellectually within the mentally retarded range with iq scores as stable as those of non-handicapped children and as accurate in predicting later academic performance.

Autism occurs more frequently in males than in females, the sex ratio is approximately 3.5 to 1 which is similar to other developmental disabilities. A lower percentage of females than this ratio predicts, however, appear to be higher functioning. Although the distribution of social class was once thought to differ with autism more frequent in the higher levels, recent studies have invalidated this assumption. Autism is equally distributed among all of the social classes and also among ethnic groups, racial groups and nationalities.

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Etiology

It is generally accepted that autism is not a single entity but a series of behaviours with multiple causes and neurological mechanisms. Of the known causes, one of the most important is genetic with several possible transmissions. Twin studies have shown a concordance rate for autism of greater than 50%. Other studies have demonstrated an increased risk of related language, speech and developmental problems in families with an autistic child. Autism is one of a number of possible outcomes for children with this genetic predisposition for communication or learning problems. Fragile x is another genetically transmitted form of autism. Although all children with this chromosomal abnormality do not have autism, 10-15% probably do.

Other identified causes of autism are infectious diseases, metabolic disorders, and structural abnormalities. Rubella is one prenatal infection that is a proven cause of autism and others are thought to exist as well. Metabolic disorders causing autism are pku and celiacs disease and it is suspected that high uric acid levels and difficulties in metabolizing purines could also be implicated. Structural abnormalities such as hydrocephalus can also cause autism; the developing technology in brain scanning equipment makes it likely that other specific structural deficits will be identified in the near future. One such deficit might relate to an under-development of the cerebellum. Though preliminary, this idea is based on the first study to suggest the specific neurological structure underlying autism. Data on the under-developed cerebellum are limited to higher functioning individuals with autism at present.

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Neurological correlates

Research evidence suggests that autism relates to specific forms of neurological dysfunction, although the precise nature of the neurological impairment remains elusive. Several investigators have identified neurological correlates of autism whose specific relationship to the disability remain unclear.

It is well documented that autistic children have more soft neurological signs that non-handicapped control groups; studies report between 40 - 100% of autistic children show at least one of these signs. Although there is considerable disagreement as to the relevance of neurological soft signs, some believe that they are indications of brain damage, immaturity or poor organisation.

Autistic people also have a higher incidence of abnormal electro-encephalograms (eegs). Studies have reported abnormal eegs in 20-65% of autistic children with abnormalities characterized by focal slowing, spiking, or paroxysmal spike-wave discharges.

In addition to a higher incidence of abnormal eegs, autistic children have seizure disorders more frequently than the general population. Current estimates are that 1/3 of autistic people develop seizure disorders, most frequently during adolescence. The adolescent onset of seizure disorders is unique to this group. There is a negative correlation between iq and seizures; seizures are more common in autistic people with lower iqs.

Finally, autism is often found in association with several nervous system difficulties; retrolental fibroplasia, tuberous sclerosis, congenital syphilis, phenylketonuria and neurolipidosis. The incidence of autism is much higher in children with these neurological conditions than in the normal population.

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Theories of autism

Most early theories of autism were psychogenic, emphasizing the role of parents in causing this severe disability of behaviour and development. Psychogenic theorists argued that parents of autistic parents were intelligent, obsessive and lacking in warmth. These theorists identified the cause of autism in the family environment and described possible mechanisms; lack of maternal communication, pathological parent-child interaction, inadequate stimulation, or reactions to parental rejection. The psycholdynamic theorists, however, have never generated supporting evidence. The only empirically verified studies concerning the emotional status of parents find that the extreme stress of being a parent of an autistic child can cause emotional difficulties. These difficulties, however, are in reaction to having an autistic child and have, in no way, been shown as a cause.

Following the decline of the psychodynamic theories, several organic theories have emerged to explain dysfunctions in autism. Theorists have identified four possible neurological explanations: overarousal of the reticular system, perceptual inconstancy associated with brain stem dysfunction, dysfunction of the limbic system and left hemisphere dysfunction.

Possible problems with the reticular system were hypothesized when autism was first recognised as an organic disorder in the 1960's. Investigators speculated that a chronically high level of non-specific activity in the reticular system might be responsible for the bizarre behaviours observed in autistic children. These behaviours were viewed as attempts to maintain continuity in the presence of this overarousal. Recent studies, however, have not shown any relationships between arousal and ouvert behaviours.

Another early organic theory of autism was perceptual inconstancy. This theory sees autism as an inability to regulate sensory input, making it impossible for autistic youngsters to develop coherent or meaningful concepts of external reality. Perceptual inconstancy has some advocates today although they have never been able to identify the precise nature of the "perceptual instabilities".

A more recent theory of autism suggests that it might be similar to amnesia arising from lesions in the limbic system. Animal models have demonstrated similarities between behaviours resulting from hippocampal lesions and those observed in autism. Although these similarities suggest consistent underlying mechanisms, there are substantial behavioural differences as well, making this theory impatible with the current state of our knowledge.

Other investigators have noted similarities between the specific cognitive and language impairments in autism and functions that are associated with the left hemisphere of the brain. Many autistic children also show superior abilities in right hemisphere functions. Because of the early onset of autism, however, left hemispheric dysfunctions should be compensated for by the right hemisphere of the brain. The apparent lack of right hemispheric compensation for left sided dysfunction suggests a bilateral dysfunction in autism.

Our present theories of autism are inadequate and incomplete. One problem is that autism is not a single entity, different causes and neurological dysfunctions are responsible for this disability in different people. As our sophistication and understanding of brain functioning increases, we can expect that the neurological theories will be more fully developed.

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Treatment

There have been 3 major approaches to treatment for children with autism over the years: psychodynamic, medical and behavioural. Psychodynamically-oriented therapies dominated the early work when autism was viewed as an emotional disorder and some of these interventions are used today. Biological interventions have included drug and vitamin therapies. Behavioural approaches have followed the principles of learning to teach appropriate behaviours and eliminate inappropriate ones in people with autism. Behavioural approaches have also emphasized special education, focusing on the development of academic and school related skills.

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