Autism Spectrum Disorder

Pervasive developmental disorders (PDD), or Autism Spectrum Disorders (ASD), range from a severe form, called Autistic Disorder, to a milder form, Asperger Syndrome.  All children with ASD have problems with social interaction, verbal and nonverbal communication, and exhibit repetitive behaviors or interests. In addition, they will often have unusual responses to sensory experiences, such as certain sounds or the way objects look. Each of these symptoms can be mild to severe, and present in each individual child differently.

The following chart, included in the DSM-IV, the diagnostic manual of the American Psychiatry Academy, details the range of symptoms that are present in 5 different types of autism spectrum disorders:

Autistic Disorder
Severely disordered verbal and non verbal language with onset prior to 3 years of age; unusual behaviors, abnormal functioning in social interaction and/or symbolic imaginative play.
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Asperger Syndrome
Relatively normal verbal language development with “milder” non-verbal language problems; limited social skills and range of interests; repetitive patterns of behavior and activities.
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Pervasive developmental disorders – Not Otherwise Specified (PDD-NOS)
Non-verbal language problems not meeting strict criteria for other pervasive development disorders; characteristics may include late age of onset, or atypical symptomatology.
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Rett’s Disorder
Rare neurodegenerative disorder present in girls in which loss of social engagement occurs early on and is accompanied by poor gait coordination and severely impaired language development.
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Childhood Disintegrative Disorder
Neurodegenerative disorder in which there is normal development during the first 2 years, followed by significant loss up till the age of 10 in at least 2 of the following areas: language development, social skills, bowel or bladder control, play, or motor skills.
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Since the DSM-IV was published, other autistic spectrum disorders have been identified as follows:

Non Verbal Learning Disabilities (NVLD)
Cluster of symptoms related to poor ability to integrate information from the right hemisphere of the brain, i.e. “see the big picture”, large motor problems, visual-spatial-orientation integration problems leading to the inability to form visual images; resulting social communication problems.
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Semantic-Pragmatic Communication Disorder
Difficulty understanding the literal meaning of words and sentences; difficulty with abstract words, words about emotions, etc.; difficulty getting central idea; trouble with conversational rules.
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Autistic spectrum symptoms are accompanied by a capacity for rote reading.  At 18-24 months hyperlexic children have taught themselves the ability to name letters and numbers.  By 3 they may read, exceeding their ability to talk.
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The classification of Autism Spectrum Disorders continues to be refined.  The problems in each disorder can overlap, cause each other, occur simultaneously in different combinations and severities, and change over time. However, it is important to continue to classify each disorder so that treatment can be customized and targeted.  This is why screening is so important, and why even a “well child” check-up should include a developmental screening test.  Several screening instruments have been developed to quickly gather information about a child's social and communicative development within medical settings. Among them are:

  • Checklist of Autism in Toddlers (CHAT)
  • Modified Checklist for Autism in Toddlers (M-CHAT)
  • Screening Tool for Autism in Two-Year-Olds (STAT)
  • Social Communication Questionnaire (SCQ) (for children 4 years of age and older) 

During the last few years, screening instruments have been devised to screen for Asperger Syndrome and higher functioning autism. The Autism Spectrum Screening Questionnaire (ASSQ), the Australian Scale for Asperger Syndrome, and the most recent, the Childhood Asperger Syndrome Test (CAST), are some of the instruments that are reliable for identification of school-age children with Asperger syndrome or higher functioning autism. These tools concentrate on social and behavioral impairments in children without significant language delay.

If a health care provider detects a problem, then a more comprehensive diagnostic evaluation performed by a multidisciplinary team (psychologist, neurologist, psychiatrist, speech therapist, etc.) will be recommended, which should include neurologic and genetic assessment, along with in-depth cognitive and language testing. In addition, measures developed specifically for diagnosing autism are often used. These include the Autism Diagnosis Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS-G). The ADI-R is a structured interview that contains over 100 items and is conducted with a caregiver.  It consists of four main factors—the child's communication, social interaction, repetitive behaviors, and age-of-onset symptoms. The ADOS-G is an observational measure used to "press" for socio-communicative behaviors that are often delayed, abnormal, or absent in children with ASD.