Cognitive Development: From the Glenn to Fontan

Written By Glory Avina

Big Picture

Toddlers with HLHS are at elevated risk for neurodevelopmental differences due to a combination of:

  • Altered brain development before birth

  • Periods of reduced oxygen delivery (especially pre-Fontan)

  • Cardiopulmonary bypass and ICU exposures

  • Medical stress, hospitalizations, and feeding challenges

Many children show subtle, uneven profiles rather than global intellectual disability.

Key Takeaways

  • HLHS toddlers post-Norwood/Glenn often have mild, uneven cognitive profiles

  • Language, attention, processing speed, and executive skills are most commonly affected

  • Fatigue and oxygenation significantly influence performance

  • Early intervention can substantially improve outcomes

  • Outcomes are highly individual and not predictive of future intelligence

A breakdown by various areas of cognitive development

1. Global Cognitive Development

  • Mildly lower average cognitive scores compared with healthy peers (often still within normal range)

  • Slower acquisition of new skills, especially under fatigue or illness

  • Greater variability day-to-day in attention and learning capacity

Important: Severe intellectual disability is not typical in the absence of major neurological injury.

2. Language Development

Common patterns

  • Delayed expressive language (talking) more than receptive language (understanding)

  • Smaller vocabulary and shorter sentences

  • Slower speech processing speed

Contributing factors

  • Prolonged intubation or reduced early vocalization

  • Frequent hospitalizations limiting language-rich interaction

  • Fatigue limiting sustained speech effort

3. Executive Function (Early Signs)

Even in toddlerhood, early executive skills may show differences:

  • Reduced working memory (holding information briefly)

  • Difficulty with task switching

  • Slower problem-solving

  • Less cognitive flexibility during play

These often become more noticeable at preschool age.

4. Attention & Processing Speed

  • Shorter attention span

  • Easily overwhelmed in noisy or busy environments

  • Slower response time to instructions

  • Fatigue significantly worsens attention

This is often physiological, not behavioral.

5. Motor–Cognitive Integration

Motor delays (common in HLHS) affect cognition indirectly:

  • Delayed crawling/walking → fewer opportunities for exploration-based learning

  • Poor endurance limits sustained play

  • Fine motor delays impact early problem-solving and play skills

6. Memory & Learning

  • Difficulty consolidating new information

  • Learning improves with repetition and structure

  • Better performance in familiar routines than novel situations

7. Sensory Processing Differences

Some toddlers exhibit:

  • Heightened sensitivity to sound, touch, or movement

  • Difficulty regulating arousal (over- or under-responsive)

  • These can interfere with attention and learning

8. Emotional Regulation & Social Cognition

  • Greater emotional reactivity or withdrawal

  • Difficulty self-soothing

  • Increased reliance on caregivers for regulation

  • Social interest is usually intact but may be fatigue-limited

9. Effects Specific to the Pre-Fontan Period

Before Fontan completion:

  • Lower oxygen saturation can affect endurance, alertness, and processing speed

  • Cognitive performance may fluctuate with hydration, illness, or oxygenation

  • Some gains accelerate after Fontan, but not all challenges resolve

10. Strengths Often Observed

Despite risks, many toddlers with HLHS show:

  • Strong social engagement

  • Good receptive language

  • Curiosity and motivation to interact

  • Resilience and adaptability in familiar environments

Glory Avina
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Summary of Glenn Head