MD Notes

creation date: 2026-08-28 16:17
tags: Pathologies

Autism Spectrum Disorder

Background

Definitions

Autism spectrum disorder (ASD) is a multifacet neurodevelopmental disorder. It is heterogeneous (spectrum) with a broad range of manifestations.

ASD has a pooled prevalence of 1.01% in North America. More males are diagnosed than females. Females who meet criteria may also not receive a prompt diagnosis due to masking skills.

Advocates generally prefer identify-first (“autistic individual”) over person-first language, and the term autism over autism spectrum disorder. This page uses ASD as it is the diagnostic terminology but care should be taken to patient preference.

Etiology

ASD is caused by a combination of genetic predisposition and environmental factors. Genetic heritability is estimated to be about 50%.

Possible environmental and perinatal factors associated include:

  • Prenatal exposure to rubella, influenza, or cytomegalovirus infections and fevers
  • Gestational diabetes and maternal obesity
  • Maternal use of SSRIs (may be confounded by pre-existing psychiatric conditions)
  • Maternal antibiotic use
  • Prenatal exposure to phthalates, air pollutants, and heavy metals

Pathophysiology

Hypotheses implicate the impairment of neural connectivity and damaged synaptogenesis. In these patients, an increased number of neurons in autistic patients impair shaping and fine-tuning of neural circuits.

Clinical Presentation

Signs & Symptoms

There is a broad range of clinical presentations:

  • Presentation within first 2 years with characteristic features (typically speech/language delays)
  • Plateau of social skills after typical early development (regression/plateau around 15-24 months)
  • Lack of interest in socializing, absent or delayed speech/language skills, marked resistance to change, restricted interests in older toddlers/preschoolers
  • Late presentation with behavioural disturbances in kindergarten or later

The clinical findings of pervasive difficulty in social communication and restricted and repetitive behaviours are described as part of the diagnostic criteria below.

Additionally, a number of associated conditions are related to ASD:

  • Intellectual impairment
  • Language impairment
  • Anxiety disorder
  • ADHD
  • Oppositional defiant disorder and other disruptive behaviour disorders
  • Depression and mood disorders
  • Tic disorders
  • Schizophrenia
  • Learning difficulties
  • Sleep problems
  • Feeding problems (sensory/texture related)
  • Epilepsy

Other findings include:

  • Motor deficits (eg. abnormal gait, clumsiness, toe walking, hypotonia)
  • Macrocephaly
  • Special skills (in memory, mathematics, music, art, or puzzles) despite profound deficiencies in other domains

History & Physical Exam

History is typically obtained from parent/caregivers. Important aspects include:

  • Early ASD symptoms (<5 years)
    • Developmental history (especially early social-emotional and language milestones)
    • Play skills and behaviours
    • Repetitive behaviours/restricted interests
    • Loss of skills
  • ASD symptoms in school-aged children
    • Social and communication behaviours to family members, peers, adults
    • Ritualized behaviours
  • Associated symptoms and conditions
    • Significant disturbances in eating, sleep, or toileting
    • Self-injury
    • Seizures
    • Depression and anxiety
    • Language and learning difficulties
    • Challenges with attention
  • Family history
    • Neurologic and developmental conditions
    • Behavioural and psychiatric conditions
    • Genetic syndromes
  • Psychosocial history (family supports, stresses, exposure to trauma)

Physical examination includes:

  • Weight
  • Head circumference
  • Neurologic exam

Diagnostic tools can be used to aid data collection but is typically used by specialist.

Diagnosis

Criteria

The diagnostic criteria according to the DSM-5-TR requires all of the following:

  • Pervasive difficulty in social communication across multiple contexts, as manifested by all of the following (currently, or by history):
    • Deficits in social-emotional reciprocity ranging from abnormal social approach to failure of normal back-and-forth conversation
    • Deficits in nonverbal communicative behaviours
    • Deficits in developing, maintaining, and understanding relationships
  • Restricted, repetitive patterns of behaviour, interests, or activities, as manifested by at least 2 of the following (currently, or by history):
    • Stereotyped or repetitive motor movements, use of objects, or speech
    • Insistence on sameness, inflexible adherence to routine, or ritualized patterns of verbal or nonverbal behaviours
    • Highly restricted, fixated interests that are abnormal in intensity of focus
    • Hyper- or hyporeactivity to sensory input or unusual interest in sensory aspects of the environment
  • Symptoms must be present in the early developmental period
  • Symptoms cause clinically significant impairment in social, occupational, or other important areas
  • Disturbances are not better explained by intellectual developmental disorder or global developmental delay

The DSM-5-TR recommends classification of the severity and level of support needed for each domain:

  • Level 1 (“Requiring support”)
  • Level 2 (“Requiring substantial support”)
  • Level 3 (“Requiring very substantial support”)

Work-up

Evaluation for associated conditions
Evaluation may include:

  • Sleep and language assessment by SLP
  • Developmental/intelligence testing
  • Vision and hearing assessment

Genetic testing may be performed.

Further laboratory studies may be indicated based on findings but there are no routine tests.

Differential

Alternative diagnoses include those that impair social skills and/or are associated with restricted or stereotypic movements.

Atypical social interaction:

  • Global delay/intellectual disability
  • Social (pragmatic) communication disorder
  • Nonverbal learning disorder
  • Attachment disorder
  • Landau-Kleffner syndrome (epileptic aphasia)

Repetitive/restricted behaviours

  • Obsessive compulsive disorder
  • Stereotypic movement disorder
  • Tic disorder/Tourette syndrome
  • Rett syndrome

Other mimics without atypical social interaction or repetitive behaviours:

  • Intellectual giftedness (especially with comorbid ADHD, learning disability, or anxiety)
  • Language disorder/language-based learning disorder
  • Hearing loss
  • Anxiety disorder
  • ADHD

Red Flags / Complications

Management

ASD is a chronic condition that requires comprehensive approach to management. Management must be individualized to the specific needs and age.

The goal of treatment is to:

  • Improve social functioning and play skills
  • Improve communication skills
  • Improve adaptive skills
  • Decrease nonfunctional or negative behaviours
  • Promote academic functioning and cognition

Management team often consist of:

  • Developmental pediatrician, child neurologist, child psychiatrist
  • Psychologist or neuropsychologist
  • Geneticist or genetics counselor
  • Speech language pathologist
  • Occupational therapist
  • Audiologist
  • Social worker

Symptom Management

ADHD

In many children with ASD, comorbid ADHD is present. ADHD medications commonly used include:

  • Biphentin
  • Concerta
  • Vyvanse

Adjunctive guanfacine may also be used.

Sleep

ASD patients often have disrupted sleep at baseline, but this is worsened if stimulants are used.

  • Melatonin (up to 10 mg) 1-2 hours before bed

Agitation

For patients with agitation concerns, a common first line option is:

  • Risperidone 1mg, titrated up as needed

References

Tools / Guidelines

Additional Reading