Neurodevelopmental Disorders

Neurodevelopmental Disorders

Overview of Neurodevelopmental Disorders in DSM-5

  • Definition: Neurodevelopmental disorders are a group of conditions with onset in the developmental period that impact personal, social, academic, or occupational functioning.
  • Characteristics:
    • Chronic and lifelong conditions.
    • Impairments range from specific to global.
    • Shift from categorical to dimensional approaches.

DSM-5 Neurodevelopmental Disorders

  • Categories:
    • Intellectual Developmental Disorder (IDD)
    • Global Developmental Delay (GDD)
    • Communication Disorders (Language Disorder, Speech Sound Disorder, Childhood-Onset Fluency Disorder, Social Communication Disorder)
    • Autism Spectrum Disorder (ASD)
    • Attention-Deficit/Hyperactivity Disorder (ADHD)
    • Specific Learning Disorder (SLD)
    • Motor Disorders (Developmental Coordination Disorder (DCD), Stereotypic Movement Disorder, Tic Disorders)
  • Specifiers: Used for individual clinical characteristics, severity of symptoms, and levels of support.

Cognition & Learning

  • Intellectual Developmental Disorder (IDD):
    • Deficits in general cognitive abilities.
    • Impacts adaptive functioning, personal independence, and social responsibility.
  • Global Developmental Delay (GDD):
    • Applies to children under 5 when expected developmental milestones are not met.
    • Considers cognitive capacity (IQ) and adaptive functioning.
  • Specific Learning Disorder (SLD):
    • Difficulties in perceiving/processing information for academic skills.
    • Unexpected academic underachievement.
    • Manifests during schooling years, including difficulties in:
      • Inaccurate or effortful reading.
      • Difficulties in comprehension, spelling, and/or writing.
      • Difficulties in mastering number sense.
    • Not a consequence of lack of learning opportunity.
  • Attention-Deficit/Hyperactivity Disorder (ADHD):
    • Characterized by inattention and/or hyperactivity-impulsivity.
    • Inconsistent with age or developmental level.
    • Can overlap with externalizing disorders in childhood.
Inattention
  • Unsustained attention during activities.
  • Mind seems elsewhere.
  • Difficulties organizing tasks and activities.
  • Distractible or forgetful.
Hyperactivity-Impulsivity
  • Overactivity or restlessness.
  • Fidgeting.
  • Difficulty waiting for a turn.
  • Interrupting or intruding on others.

Lived Experience: ADHD

  • Frustration with repeated failures despite best efforts.
  • Inability to filter and prioritize stimuli.
  • Paradoxical perfectionism combined with struggles in simple tasks.
  • Feeling like a mismatch to societal expectations.
  • Importance of self-awareness and positive reinforcement.
  • Value of acceptance and recognizing diverse competencies.

Social & Communication

  • Communication Disorders:
    • Language Disorder
    • Speech Sound Disorder
    • Social (Pragmatic) Communication Disorder (SPCD)
  • Social (Pragmatic) Communication Disorder (SPCD):
    • Social impairments not explained by low abilities in structural language, IDD, or ASD.
  • Childhood-Onset Fluency Disorder (Stuttering):
    • Disturbance of normal fluency and motor production of speech.
  • Autism Spectrum Disorder (ASD):
    • Umbrella term (DSM-5) for previously separate disorders:
      • Autistic disorder
      • Pervasive developmental disorder-not otherwise specified
      • Childhood disintegrative disorder
      • Asperger’s Disorder
    • Difficulties in social communication and social interaction.
    • Restricted, repetitive patterns of behavior.
  • Specifiers: Used for individual clinical characteristics, severity of symptoms, and levels of support.

Lived Experience: ASD

  • Sensory sensitivities (e.g., discomfort with bright lights and noises).

Motor & Coordination

  • Developmental Coordination Disorder (DCD):
    • Impairment in coordinated motor skills.
    • Manifests as clumsiness, slowness, or inaccuracy of performance.
    • Young children may show delays in motor milestones.
    • Movement execution may be awkward, slow, or less precise.
    • Handwriting competence is frequently affected (impact distinguished from SLD).
  • Stereotypic Movement Disorder:
    • Repetitive, driven, seemingly purposeless motor behaviors.
    • Individually patterned 'signature' behavior.
    • Specifiers: with or without self-injurious behavior.
  • Tic Disorder:
    • Sudden, rapid, recurrent, and nonrhythmic motor movements or vocalizations (e.g., Tourette’s disorder).
    • Localized uncomfortable sensation prior to a tic.

Lived Experience: DCD

  • Impact for DCD Report:
    • Largest survey in Australia to identify challenges experienced by children with DCD and their families.
    • Domains: diagnosis, activity and participation, education, therapy, and social and emotional health.
    • Responses from 443 children aged 4-18 years (73.5% male).
Key Findings from Impact for DCD Report
  • Diagnosis:
    • Many children are not diagnosed until two to four years after seeking help.
    • Inconsistent terminology and standardized practice in Australia.
    • 37% of parents reported diagnosis was helpful but were frustrated by inconsistent and inaccurate labeling.
    • Nine separate diagnostic terms used; more children diagnosed with dyspraxia than DCD.
  • Activity and Participation:
    • Top five difficult activities: dressing, eating using utensils, self-care, drawing/writing, and using scissors.
    • 84% of families reported their child was more tired at the end of the day than other children.
    • 49% reported their child did not enjoy physical activity.
    • 61% of parents were concerned about the impact their child's movement difficulties were having on their physical health.
  • Education:
    • 82% of parents felt movement difficulties negatively impacted education.
    • Top challenges: teacher awareness, fatigue, keeping up in class, making friends, inclusion in playground, and bullying.
    • Most parents reported their child's learning needs were not being met.

Co-morbidities

  • Co-occurrences of two or more different disorders.
  • Common; can exacerbate functional impairments.
  • Inconsistencies in prevalence due to heterogeneity across studies (samples, design).
  • Concurrent vs. successive comorbidities.
  • Possible common aetiology or neural pathways.

Neuroimaging Findings: ADHD, ASD & DCD

  • Why Neuroimaging in NDDs?
    • Reveal structural differences (e.g., reduced prefrontal cortex, hippocampus in IDD).
    • Map functional connectivity (e.g., altered connectivity in language-related areas in communication disorders).
    • Track brain development over time or lifespan (e.g., accelerated brain growth in ASD during infancy, slowed growth afterward).
    • Aid early diagnosis and/or intervention (e.g., early biomarkers, early identifications and supports).
    • Link brain-behavior relationships (e.g., reduced activity in prefrontal cortex in ADHD related to impulse control).
    • Assess and personalize interventions (e.g., changes following intervention, not a one-size-fits-all approach).

Structural and Functional Studies

  • Structural neuroimaging in ADHD (e.g., brain volumes, cortical thinning).
  • Functional neuroimaging in ASD (e.g., brain connectivity and activation).
  • Structural and/or functional neuroimaging in DCD (e.g., white matter, connectivity).
ADHD: Grey Matter and Subcortical Volumes
  • Whole and subcortical region volume reduction.
    • Hoogman et al. (2017): Smaller volumes of subcortical regions in ADHD (only in children); delayed subcortical volume maturation.
  • Grey matter volume reduction.
    • Global.
    • Prefrontal cortex, basal ganglia, cerebellum.
    • Maier et al. (2016): Reduction in grey matter in ADHD is global rather than localized.
ADHD: Cortical Thinning and Maturation
  • Developmental cortical changes involve growth of neurons and synapses, followed by synaptic pruning.
  • Patterns of cortical thinning in ADHD involve delayed trajectory of cortical maturation.
    • Shaw et al. (2011): Higher levels of hyperactivity/impulsivity related to slower rate of cortical thinning; children with ADHD had slowest rate of thinning; continuum of symptoms.
ASD: Social Network Connectivity
  • Underconnectivity in regions related to processing of social information.
    • Hoffmann et al. (2016): Processing of facial, vocal, and audiovisual social signals; reduced connectivity between temporal voice area (TVA) and frontal brain areas; higher AQ traits, lower connectivity.
ASD: Sensory Responses
  • Increased activation in sensory cortices, suggesting differential processing of sensory information.
    • Green et al. (2013): Greater activation in primary sensory cortical areas in ASD; increased brain activation related to higher sensory over-responsivity during mildly aversive stimuli presentation (fMRI).
ASD: Cognitive Flexibility
  • Differences in activation in regions related to switching/set-shifting tasks.
    • Yerys et al. (2015): Wisconsin Card Sorting Test; 'switch cost' in both groups, ASD less accurate; similar regions activated, but altered levels of connectivity in ASD.
DCD: White Matter Structure
  • Reductions in white matter microstructure in those with DCD.
    • Brown-Lum et al. (2020): Diffusion Tensor Imaging (DTI); lower fractional anisotropy (FA) and axial diffusivity (AD) in white matter regions in DCD; lower FA & AD can indicate reduced structural integrity or disorganisation of white matter tracts.
DCD: Altered Connectivity
  • Altered connectivity between sensorimotor network and other brain regions in DCD.
    • Rinat et al. (2020): Resting fMRI to identify brain regions with parallel activation; less functional connectivity between sensory motor network and other areas (e.g., posterior cingulate cortex, posterior middle temporal gyrus) in DCD.

Inconsistencies in Findings

  • Variability in study design (e.g., sample size, participant characteristics, imaging techniques).
  • Inconsistencies in diagnostic criteria (e.g., diagnostic variability, subtypes, or heterogenous presentations).
  • Methodological differences (e.g., data acquisition or processing, control groups, functional vs. structural findings).

Examples of Meta-Analyses and Systematic Reviews

  • Brain alterations in children/adolescents with ADHD revisited: A neuroimaging meta-analysis of 96 structural and functional studies.
  • A systematic review and meta-analysis of the fMRI investigation of autism spectrum disorders.
  • Behavioral and Neuroimaging Research on Developmental Coordination Disorder (DCD): A Combined Systematic Review and Meta-Analysis of Recent Findings.
  • Cognitive and neuroimaging findings in developmental coordination disorder: new insights from a systematic review of recent research.

Future Research

  • Longitudinal studies (e.g., track changes and trajectories over time).
  • Multimodal approaches (e.g., combining techniques, integrating other types of data).
  • Standardisation of protocols and methods (e.g., reduce variability across studies, improve comparability of findings).

Diagnostic Assessments

  • Diagnoses rely on behavioural presentations.

    • Clinical interviews, standardised assessments, behavioural checklists and observations.

  • Range of cognitive and behavioral domains:

    • Attention
    • Learning & memory
    • Language ability

  • Combination of tests for a more comprehensive understanding of individual cognitive profile.

  • Useful in both diagnosing and ruling out NDDs.

    • Assessing impaired and intact skills in key cognitive domains.
    • Simplified example: A child with academic struggles (reading) and difficulties focusing in school:
      • SLD? ADHD?
      • Reading & phonological processing tests (SLD).
      • Attention/executive functioning tests (ADHD).
      • Comorbidities?

Suitability/Appropriateness of Tests

  • Age considerations
    • Age-appropriate norms and tests designed for correct developmental stage
  • Cultural and socioeconomic backgrounds
  • Language and communication proficiency
  • Sensory and motor impairments

Lecture Take Aways

  • Neurodevelopmental disorders are complex and heterogenous.
  • Ongoing research in neuroimaging will continue to enhance our understanding.
  • Thoughtful approaches to assessments can lead to more reliable results and appropriate supports.
  • Remember the people behind the diagnoses.