Asperger syndrome

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Overview
Asperger's syndrome (also called Asperger syndrome, Asperger's disorder, Asperger's or AS) is the autism spectrum disorder (ASD) in which there is no general delay in language or cognitive development. As in other ASDs, people with AS have difficulties in social interaction and restricted, stereotyped patterns of behavior, interests and activities. Although not mentioned in standard diagnostic criteria for AS, physical clumsiness and atypical use of language are frequently reported.

Asperger's syndrome is named after Austrian pediatrician Hans Asperger who, in 1944, described children in his practice who lacked nonverbal communication skills, demonstrated limited empathy with their peers, and were physically clumsy. Fifty years later, AS was standardized as a diagnosis, but questions about many aspects of AS remain. For example, there is lingering doubt about the distinction between AS and high-functioning autism (HFA); partly due to this, the prevalence of AS is not firmly established. The exact cause of AS is unknown, although research supports the likelihood of a genetic basis; brain imaging techniques have not identified a clear common pathology.

There is no single treatment for Asperger's syndrome, and the effectiveness of particular interventions is supported by only limited data. Intervention is aimed at improving symptoms and function. The mainstay of management is behavioral therapy, focusing on specific deficits to address poor communication skills, obsessive or repetitive routines, and physical clumsiness. Most individuals with AS can learn to cope with their differences, but may continue to need moral support and encouragement to maintain an independent life. Researchers and people with AS have advocated a shift in attitudes toward the view that AS is a difference, rather than a disability that must be treated or cured.

Classification
Asperger's syndrome is one of the autism spectrum disorders (ASD) or pervasive developmental disorders (PDD), which are a spectrum of psychological conditions that are characterized by abnormalities of social interaction and communication that pervade the individual's functioning, and by restricted and repetitive interests and behavior. Like other psychological development disorders, ASD begins in infancy or childhood, has a steady course without remission or relapse, and has impairments that result from maturation-related changes in various systems of the brain. ASD, in turn, is a subset of the broader autism phenotype (BAP), which describes individuals who may not have ASD but do have autistic-like traits, such as social deficits. Of the other four ASD forms, autism is the most similar to AS in signs and likely causes but its diagnosis requires impaired communication and allows delay in cognitive development; Rett syndrome and childhood disintegrative disorder share several signs with autism, but may have unrelated causes; and pervasive developmental disorder not otherwise specified (PDD-NOS) is diagnosed when the criteria for a more specific disorder are unmet. The extent of the overlap between AS and high-functioning autism (HFA—autism unaccompanied by mental retardation) is unclear. The current ASD classification may not reflect the true nature of the conditions.

Characteristics
A pervasive developmental disorder, Asperger's syndrome is distinguished by a pattern of symptoms rather than a single symptom. It is characterized by qualitative impairment in social interaction, by stereotyped and restricted patterns of behavior, activities and interests, and by no clinically significant delay in cognitive development or general delay in language. Intense preoccupation with a narrow subject, one-sided verbosity, restricted prosody, and physical clumsiness are typical of the condition, but are not required for diagnosis.

Social interaction
The lack of demonstrated empathy is possibly the most dysfunctional aspect of Asperger syndrome. Individuals with Asperger's syndrome experience difficulties in basic elements of social interaction, which may include a failure to develop friendships or to seek shared enjoyments or achievements with others (for example, showing others objects of interest); a lack of social or emotional reciprocity; and impaired nonverbal behaviors in areas such as eye contact, facial expression, posture, and gesture.

Unlike those with autism, people with AS are not usually withdrawn around others; they approach others, even if awkwardly, for example by engaging in a one-sided, long-winded speech about a favorite topic while being oblivious to the listener's feelings or reactions, such as signs of boredom or haste to leave. This social awkwardness has been called "active but odd". This failure to react appropriately to social interaction may appear as disregard for other people's feelings, and may come across as insensitive. The cognitive ability of children with AS often lets them articulate social norms in a laboratory context, where they may be able to show a theoretical understanding of other people’s emotions; they typically have difficulty acting on this knowledge in fluid, real-life situations, however. People with AS may analyze and distill their observation of social interaction into rigid behavioral guidelines and apply these rules in awkward ways—such as forced eye contact—resulting in demeanor that appears rigid or socially naïve. Childhood desires for companionship can be numbed through a history of failed social encounters.

The hypothesis that individuals with AS are predisposed to violent or criminal behavior has been investigated but is not supported by data. More evidence suggests children with AS are victims rather than victimizers.

Restricted and repetitive interests and behavior
People with Asperger syndrome display behavior, interests, and activities that are restricted and repetitive and are sometimes abnormally intense or focused. They may stick to inflexible routines or rituals, move in stereotyped and repetitive ways, or preoccupy themselves with parts of objects.

Pursuit of specific and narrow areas of interest is one of the most striking features of AS. Individuals with AS may collect volumes of detailed information on a relatively narrow topic such as dinosaurs or deep fat fryers, without necessarily having genuine understanding of the broader topic. For example, a child might memorize camera model numbers while caring little about photography. This behavior is usually apparent by grade school, typically age 5 or 6 in the United States. Although these special interests may change from time to time, they typically become more unusual and narrowly focused, and often dominate social interaction so much that the entire family may become immersed. Because topics such as dinosaurs often capture the interest of children, this symptom may go unrecognized.

Stereotyped and repetitive motor behaviors are a core part of the diagnosis of AS and other ASDs. They include hand movements such as flapping or twisting, and complex whole-body movements. These are typically repeated in longer bursts and look more voluntary or ritualistic than tics, which are usually faster, less rhythmical and less often symmetrical.

Speech and language
Although individuals with Asperger syndrome acquire language skills without significant general delay and their speech typically lacks significant abnormalities, language acquisition and use is often atypical. Abnormalities include verbosity; abrupt transitions; literal interpretations and miscomprehension of nuance; use of metaphor meaningful only to the speaker; auditory perception deficits; unusually pedantic, formal or idiosyncratic speech; and oddities in loudness, pitch, intonation, prosody, and rhythm.

Three aspects of communication patterns are of clinical interest: poor prosody, tangential and circumstantial speech, and marked verbosity. Although inflection and intonation may be less rigid or monotonic than in autism, people with AS often have a limited range of intonation; speech may be unusually fast, jerky or loud. Speech may convey a sense of incoherence; the conversational style often includes monologues about topics that bore the listener, fails to provide context for comments, or fails to suppress internal thoughts. Individuals with AS may fail to monitor whether the listener is interested or engaged in the conversation. The speaker's conclusion or point may never be made, and attempts by the listener to elaborate on the speech's content or logic, or to shift to related topics, are often unsuccessful.

Children with AS may have an unusually sophisticated vocabulary at a young age and have been colloquially called "little professors", but have difficulty understanding figurative language and tend to use language literally. Children with AS appear to have particular weaknesses in areas of nonliteral language that include humor, irony, and teasing. Although individuals with AS usually understand the cognitive basis of humor they seem to lack understanding of the intent of humor to share enjoyment with others. Despite strong evidence of impaired humor appreciation, there are anecdotal reports of humor in individuals with AS, which challenge theories of humor in AS.

Other
Individuals with Asperger syndrome may have signs or symptoms that are independent of the diagnosis, but can affect the individual or the family. These include differences in perception and problems with motor skills, sleep, and emotions.

Individuals with AS often have excellent auditory and visual perception. Children with ASD often demonstrate enhanced perception of small changes in patterns such as arrangements of objects or well-known images; typically this is domain-specific and involves processing of fine-grained features. Conversely, compared to individuals with HFA, individuals with AS have deficits in some tasks involving visual-spatial perception, auditory perception, or visual memory. Many accounts of individuals with AS and ASD report other unusual sensory and perceptual skills and experiences. They may be unusually sensitive or insensitive to sound, light, touch, texture, taste, smell, pain, temperature, and other stimuli, and they may exhibit synesthesia; these sensory responses are found in other developmental disorders and are not specific to AS or to ASD. There is little support for increased fight-or-flight response or failure of habituation in autism; there is more evidence of decreased responsiveness to sensory stimuli, although several studies show no differences.

Hans Asperger’s initial accounts and other diagnostic schemes include descriptions of physical clumsiness. Children with AS may be delayed in acquiring skills requiring motor dexterity, such as riding a bicycle or opening a jar, and may seem to move awkwardly or feel "uncomfortable in their own skin". They may be poorly coordinated, or have an odd or bouncy gait or posture, poor handwriting, or problems with visual-motor integration. They may show problems with proprioception (sensation of body position) on measures of apraxia (motor planning disorder), balance, tandem gait, and finger-thumb apposition. There is no evidence that these motor skills problems differentiate AS from other high-functioning ASDs.

Children with AS are more likely to have sleep problems, including difficulty in falling asleep, frequent nocturnal awakenings, and early morning awakenings. AS is also associated with high levels of alexithymia, which is difficulty in identifying and describing one's emotions. Although AS, lower sleep quality, and alexithymia are associated, their causative relationship is unclear.

Causes
Hans Asperger described common symptoms among his patients' family members, especially fathers, and research supports this observation and suggests a genetic contribution to Asperger syndrome. Although no specific gene has yet been identified, multiple factors are believed to play a role in the expression of autism, given the phenotypic variability seen in this group of children. Evidence for a genetic link is the tendency for AS to run in families and an observed higher incidence of family members who have behavioral symptoms similar to AS but in a more limited form (for example, slight difficulties with social interaction, language, or reading). Most research suggests that all autism spectrum disorders have shared genetic mechanisms, but AS may have a stronger genetic component than autism. There is probably a common group of genes where particular alleles render an individual vulnerable to developing AS; if this is the case, the particular combination of alleles would determine the severity and symptoms for each individual with AS.

A few ASD cases have been linked to exposure to teratogens (agents that cause birth defects) during the first eight weeks from conception. Although this does not exclude the possibility that ASD can be initiated or affected later, it is strong evidence that it arises very early in development. Many environmental factors have been hypothesized to act after birth, but none has been confirmed by scientific investigation.

Mechanism
Asperger syndrome appears to result from developmental factors that affect many or all functional brain systems, as opposed to localized effects. Although the specific underpinnings of AS or factors that distinguish it from other ASDs are unknown, and no clear pathology common to individuals with AS has emerged, it is still possible that AS's mechanism is separate from other ASD. Neuroanatomical studies and the associations with teratogens strongly suggest that the mechanism includes alteration of brain development soon after conception. Abnormal migration of embryonic cells during fetal development may affect the final structure and connectivity of the brain, resulting in alterations in the neural circuits that control thought and behavior. Several theories of mechanism are available; none are likely to be complete explanations.

The underconnectivity theory hypothesizes underfunctioning high-level neural connections and synchronization, along with an excess of low-level processes. It maps well to general-processing theories such as weak central coherence theory, which hypothesizes that a limited ability to see the big picture underlies the central disturbance in ASD. A related theory—enhanced perceptual functioning—focuses more on the superiority of locally oriented and perceptual operations in autistic individuals.

The mirror neuron system (MNS) theory hypothesizes that alterations to the development of the MNS interfere with imitation and lead to Asperger's core feature of social impairment. For example, one study found that activation is delayed in the core circuit for imitation in individuals with AS. This theory maps well to social cognition theories like the theory of mind, which hypothesizes that autistic behavior arises from impairments in ascribing mental states to oneself and others, or hyper-systemizing, which hypothesizes that autistic individuals can systematize internal operation to handle internal events but are less effective at empathizing by handling events generated by other agents.

Other possible mechanisms include serotonin dysfunction and cerebellar dysfunction.

Screening
Parents of children with Asperger syndrome can typically trace differences in their children's development to as early as 30 months of age. Developmental screening during a routine check-up by a general practitioner or pediatrician may identify signs that warrant further investigation. The diagnosis of AS is complicated by the use of several different screening instruments, including the Asperger Syndrome Diagnostic Scale (ASDS), Autism Spectrum Screening Questionnaire (ASSQ), Childhood Asperger Syndrome Test (CAST), Gilliam Asperger’s Disorder Scale (GADS), Krug Asperger’s Disorder Index (KADI), and the Autism Spectrum Quotient (AQ). None have been shown to reliably differentiate between AS and other ASDs.

Diagnosis
Standard diagnostic criteria require impairment in social interaction, and repetitive and stereotyped patterns of behavior, activities and interests, without significant delay in language or cognitive development. Unlike the international standard, U.S. criteria also require significant impairment in day-to-day functioning. Other sets of diagnostic criteria have been proposed by Szatmari et al. and by Gillberg and Gillberg.

Diagnosis is most commonly made between the ages of four and eleven. A comprehensive assessment involves a multidisciplinary team  that observes across multiple settings, and includes neurological and genetic assessment as well as tests for cognition, psychomotor function, verbal and nonverbal strengths and weaknesses, style of learning, and skills for independent living. The current "gold standard" in diagnosing ASDs combines clinical judgment with the Autism Diagnostic Interview-Revised (ADI-R)—a semistructured parent interview—and the Autism Diagnostic Observation Schedule (ADOS)—a conversation and play-based interview with the child. Delayed or mistaken diagnosis can be traumatic for individuals and families; for example, misdiagnosis can lead to medications that worsen behavior. Many children with AS are initially misdiagnosed with attention-deficit hyperactivity disorder (ADHD). Diagnosing adults is more challenging, as standard diagnostic criteria are designed for children and the expression of AS changes with age. Conditions that must be considered in a differential diagnosis include other ASDs, the schizophrenia spectrum, ADHD, obsessive compulsive disorder, depression, semantic pragmatic disorder, nonverbal learning disorder, Tourette syndrome, stereotypic movement disorder and bipolar disorder.

Underdiagnosis and overdiagnosis are problems in marginal cases. The cost of screening and diagnosis and the challenge of obtaining payment can inhibit or delay diagnosis. Conversely, the increasing popularity of drug treatment options and the expansion of benefits has motivated providers to overdiagnose ASD. There are indications AS has been diagnosed more frequently in recent years, partly as a residual diagnosis for children of normal intelligence who do not have autism but have social difficulties. There are questions about the external validity of the AS diagnosis, that is, it is unclear whether there is a practical benefit in distinguishing AS from HFA and from PDD-NOS; the same child can receive different diagnoses depending on the screening tool.

Management
Asperger syndrome treatment attempts to manage distressing symptoms and to teach age-appropriate social, communication and vocational skills that are not naturally acquired during development, with intervention tailored to the needs of the individual child, based on multidisciplinary assessment. Although progress has been made, data supporting the efficacy of particular interventions are limited.

The ideal treatment for AS coordinates therapies that address core symptoms of the disorder, including poor communication skills and obsessive or repetitive routines. While most professionals agree that the earlier the intervention, the better, there is no single best treatment package. AS treatment resembles that of other high-functioning ASDs, except that it takes into account the linguistic capabilities, verbal strengths, and nonverbal vulnerabilities of individuals with AS. A typical program generally includes:
 * the training of social skills for more effective interpersonal interactions;
 * cognitive behavioral therapy to improve stress management relating to anxiety or explosive emotions, and to cut back on obsessive interests and repetitive routines;
 * medication, for coexisting conditions such as depression and anxiety;
 * occupational or physical therapy to assist with poor sensory integration and motor coordination;
 * social communication intervention, which is specialized speech therapy to help with the pragmatics of the give and take of normal conversation;
 * the training and support of parents, particularly in behavioral techniques to use in the home.

Of the many studies on behavior-based early intervention programs, most are case studies of up to five participants, and typically examine a few problem behaviors such as self-injury, aggression, noncompliance, stereotypies, or spontaneous language; unintended side effects are largely ignored. Despite the popularity of social skills training, its effectiveness is not firmly established. A randomized controlled study of a model for training parents in problem behaviors in their children with AS showed that parents attending a one-day workshop or six individual lessons reported fewer behavioral problems, while parents receiving the individual lessons reported less intense behavioral problems in their AS children. Vocational training is important to teach job interview etiquette and workplace behavior to older children and adults with AS, and organization software and personal data assistants to improve the work and life management of people with AS are useful.

No medications directly treat the core symptoms of AS. Although research into the efficacy of pharmaceutical intervention for AS is limited, it is essential to diagnose and treat comorbid conditions. Deficits in self-identifying emotions or in observing effects of one's behavior on others can make it difficult for individuals with AS to see why medication may be appropriate. Medication can be effective in combination with behavioral interventions and environmental accommodations in treating comorbid symptoms such as anxiety, depression, inattention and aggression. The atypical neuroleptic medications risperidone and olanzapine have been shown to reduce the associated symptoms of AS; risperidone can reduce repetitive and self-injurious behaviors, aggressive outbursts and impulsivity, and improve stereotypical patterns of behavior and social relatedness. The selective serotonin reuptake inhibitors (SSRIs) fluoxetine, fluvoxamine and sertraline have been effective in treating restricted and repetitive interests and behaviors.

Care must be taken with medications; abnormalities in metabolism, cardiac conduction times, and an increased risk of type 2 diabetes have been raised as concerns with these medications, along with serious long-term neurological side effects. SSRIs can lead to manifestations of behavioral activation such as increased impulsivity, aggression and sleep disturbance. Weight gain and fatigue are commonly reported side effects of risperidone, which may also lead to increased risk for extrapyramidal symptoms such as restlessness and dystonia and increased serum prolactin levels. Sedation and weight gain are more common with olanzapine, which has also been linked with diabetes. Sedative side-effects in school-age children have ramifications for classroom learning. Individuals with AS may be unable to identify and communicate their internal moods and emotions or to tolerate side effects that for most people would not be problematic.

Prognosis
There is some evidence that as many as 20% of children with AS "grow out" of it, and fail to meet the diagnostic criteria as adults. As of 2006, no studies addressing the long-term outcome of individuals with Asperger syndrome are available and there are no systematic long-term follow-up studies of children with AS. Individuals with AS appear to have normal life expectancy but have an increased prevalence of comorbid psychiatric conditions such as depression and anxiety that may significantly affect prognosis. Although social impairment is lifelong, outcome is generally more positive than with individuals with lower functioning autism spectrum disorders; for example, ASD symptoms are more likely to diminish with time in children with AS or HFA. Although most students with AS/HFA have average mathematical ability and test slightly worse in mathematics than in general intelligence, some are gifted in mathematics and AS has not prevented some adults from major accomplishments such as winning the Nobel Prize.

Children with AS may require special education services because of their social and behavioral difficulties although many attend regular education classes. Adolescents with AS may exhibit ongoing difficulty with self-care, organization and disturbances in social and romantic relationships; despite high cognitive potential, most remain at home, although some do marry and work independently. The "different-ness" adolescents experience can be traumatic. Anxiety may stem from preoccupation over possible violations of routines and rituals, from being placed in a situation without a clear schedule or expectations, or from concern with failing in social encounters; the resulting stress may manifest as inattention, withdrawal, reliance on obsessions, hyperactivity, or aggressive or oppositional behavior. Depression is often the result of chronic frustration from repeated failure to engage others socially, and mood disorders requiring treatment may develop.

Education of families is critical in developing strategies for understanding strengths and weaknesses; helping the family to cope improves outcome in children. Prognosis may be improved by diagnosis at a younger age that allows for early interventions, while interventions in adulthood are valuable but less beneficial. There are legal implications for individuals with AS as they run the risk of exploitation by others and may be unable to comprehend the societal implications of their actions.

Epidemiology
Prevalence estimates vary enormously. A 2003 review of epidemiological studies of children found prevalence rates ranging from 0.03 to 4.84 per 1,000, with the ratio of autism to Asperger syndrome ranging from 1.5:1 to 16:1; combining the average ratio of 5:1 with a conservative prevalence estimate for autism of 1.3 per 1,000 suggests indirectly that the prevalence of AS might be around 0.26 per 1,000. Part of the variance in estimates arises from differences in diagnostic criteria. For example, a relatively small 2007 study of 5,484 eight-year-old children in Finland found 2.9 children per 1,000 met the ICD-10 criteria for an AS diagnosis, 2.7 per 1,000 for Gillberg and Gillberg criteria, 2.5 for DSM-IV, 1.6 for Szatmari et al., and 4.3 per 1,000 for the union of the four criteria. Boys seem to be at higher risk for AS than girls; estimates of the sex ratio range from 1.6:1 to 4:1, using the Gillberg and Gillberg criteria.

Anxiety and depression are the most common other conditions seen at the same time; comorbidity of these in persons with AS is estimated at 65%. Depression is common in adolescents and adults; children are likely to present with ADHD. Reports have associated AS with medical conditions such as aminoaciduria and ligamentous laxity, but these have been case reports or small studies and no factors have been associated with AS across studies. One study of males with AS found an increased rate of epilepsy and a high rate (51%) of nonverbal learning disorder. AS is associated with tics, Tourette syndrome, and bipolar disorder, and the repetitive behaviors of AS have many similarities with the symptoms of obsessive-compulsive disorder and obsessive-compulsive personality disorder. Although many of these studies are based on psychiatric clinic samples without using standardized measures, it seems reasonable to conclude that comorbid conditions are relatively common.

History
Named after the Austrian pediatrician Hans Asperger (1906–80), Asperger syndrome is a relatively new diagnosis in the field of autism. In 1944, Asperger described four children in his practice who had difficulty in integrating themselves socially. The children lacked nonverbal communication skills, failed to demonstrate empathy with their peers, and were physically clumsy. Asperger called the condition "autistic psychopathy" and described it as primarily marked by social isolation. Unlike today's AS, autistic psychopathy could be found in people of all levels of intelligence, including those with mental retardation. He called his young patients "little professors", and believed some would be capable of exceptional achievement and original thought later in life. His paper was published during wartime and in German, so it was not widely read elsewhere.

Lorna Wing popularized the term Asperger syndrome in the English-speaking medical community in her 1981 publication of a series of case studies of children showing similar symptoms, and Uta Frith translated Asperger's paper to English in 1991. Sets of diagnostic criteria were outlined by Gillberg and Gillberg in 1989 and by Szatmari et al. in the same year. AS became a standard diagnosis in 1992, when it was included in the tenth edition of the World Health Organization’s diagnostic manual, International Classification of Diseases (ICD-10); in 1994, it was added to the fourth edition of the American Psychiatric Association's diagnostic reference, Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

Hundreds of books, articles and websites now describe AS, and prevalence estimates have increased dramatically for ASD, with AS recognized as an important subgroup. Whether it should be seen as distinct from high-functioning autism is a fundamental issue requiring further study. There is little consensus among clinical researchers about the use of the terms Asperger's syndrome or Asperger's disorder, and there are questions about the empirical validation of the DSM-IV and ICD-10 criteria.

Cultural aspects
People with Asperger syndrome may refer to themselves in casual conversation as aspies, coined by Liane Holliday Willey in 1999. The word neurotypical (abbreviated NT) describes a person whose neurological development and state are typical, and is often used to refer to non-autistic people. The Internet has allowed individuals with AS to communicate and celebrate with each other in a way that was not previously possible due to their rarity and geographic dispersal. A subculture of aspies has formed. Internet sites like Wrong Planet have made it easier for individuals to connect.

Autistic people have contributed to a shift in perception of autism spectrum disorders as complex syndromes rather than diseases that must be cured. Proponents of this view reject the notion that there is an "ideal" brain configuration and that any deviation from the norm is pathological; they promote tolerance for what they call neurodiversity. These views are the basis for the autistic rights and autistic pride movements.

Simon Baron-Cohen has argued that AS and high-functioning autism are different cognitive styles, not disabilities, and that a diagnosis of AS/HFA should not be received as a family tragedy, but as interesting information, such as learning that a child is left-handed. According to Baron-Cohen, "people with AS/HFA might not necessarily be disabled in an environment in which an exact mind, attracted to detecting small details, is an advantage." Tony Attwood argues, "the unusual profile of abilities that we define as Asperger's syndrome has probably been an important and valuable characteristic of our species throughout evolution."