Typical Neurological Development
- Morphological and Functional Development
- Development of the CNS is highly coordinated and complex.
- Morphological disorders (CNS malformations) can arise due to genetic or external factors such as inflammation and maternal substance abuse.
- Traditional classifications of CNS malformations are based on phenotypical and temporal criteria (proliferation, migration, organization).
- Recent classifications incorporate aetiological (especially genetic) factors.
- Timing of injury influences morphological outcomes significantly, e.g. in cerebral palsy.
- Brain maturation continues postnatally, extending into adulthood.
- Brain plasticity and reorganization are inherent to immature brains, facilitating recovery post-injury.
- Language and motor areas can reorganize functionally, depending on lesion timing and extent.
- Neuronal Group Selection Theory (NGST)
- Interaction between genetic and environmental determinants shapes infant motor activity.
- Motor pattern selection from abundant variations occurs at specific ages relevant to each function.
- see Neuronal Group Selection Theory (NGST)
Main Stages of CNS Development
- 2 weeks: Neural plate formation (enterogenous cysts, fistulae).
- 3−4 weeks: Dorsal induction/neurulation (blastopathies: anencephaly, encephaloceles, spina bifida, meningoceles).
- 4−7 weeks: Caudal neural-tube formation (diastematomyelia, Dandy-Walker syndrome, cerebellar hypoplasia).
- 5−6 weeks: Ventral induction (holoprosencephaly, median cleft face syndrome).
- 8−16 weeks: Neuronal/glial proliferation (microcephaly, megalencephaly).
- 12−20 weeks: Migration (lissencephaly, heterotopias, agenesis corpus callosum).
- 24 weeks onwards: Organization (polymicrogyria, cortical dysplasias).
- 24 weeks to 2 years post-term: Myelination (dysmyelination, white matter damage, cortical-subcortical damage).
Typical Developmental Milestones
- Wide biological variation in milestone attainment (e.g., walking from 8-18 months).
- Developmental milestones in preterm infants adjusted by corrected age for first 2 years.
- Milestones typically follow a predictable sequence with intermittent rapid progress and stable periods.
- Skills acquired typically not lost in normal development.
- No significant sex differences in motor or language milestones.
- Developmental screening important for early intervention opportunities.
Gross Motor Milestones (WHO Standards)
- Sitting without support: by 9 months
- Hands-and-knees crawling: by 14 months
- Standing with assistance: by 11 months
- Walking with assistance: by 14 months
- Standing alone: by 17 months
- Walking alone: by 18 months
Fine Motor Milestones
- Reaching for an object: by 4 months
- Grasping with whole hand: by 5 months
- Transferring objects hand to hand: by 7 months
- Pincer grasp: by 11 months
Language and Social Milestones
- Canonical babbling: 6−10 months
- Recognizing name: 8 months
- Understanding single words: 8−10 months
- First true words: 10−12 months
- Social smile: by 3 months
- Stranger anxiety: around 7 months
- Interactive play and joint attention: 8−12 months
- Absence of these milestones requires further assessment (visual/hearing/autism evaluation).
Structured Neurodevelopmental Scales
- Scales evaluate functioning rather than providing categorical diagnoses.
- Multidimensional profiles common; some scales are unidimensional.
- Scales must be administered by trained examiners; time-consuming but valuable.
- Examples:
- Bayley Scales of Infant and Toddler Development
- Griffiths Mental Development Scales
- Mullen Scales of Early Learning
- Battelle Developmental Inventory
- Alberta Infant Motor Scale
| Name | Age Range | Duration | Domains |
|---|---|---|---|
| Bayley Scales of Infant Development, Second Edition | 1−42 months | 25−60 min | Mental Development, Motor Development, Behaviour Rating Scale |
| Bayley Scales of Infant and Toddler Development, Third Edition | 1−42 months | 30−90 min | Cognitive, Language, Motor, Social-Emotional (parent report), Adaptive Behaviour (parent report) |
| Griffiths Scales of Child Development, Third Edition | Birth to 6 years | 35−60 min | Foundations of Learning, Language and Communication, Eye and Hand Coordination, Personal-Social-Emotional, Gross Motor |
| Mullen Scales of Early Learning | Birth to 5 years 8 months | 15−30 min (depends on age) | Gross Motor, Fine Motor, Visual Reception, Receptive Language, Expressive Language |
| Battelle Developmental Inventory II | Birth to 8 years | 1−2 h | Personal-Social, Adaptive, Motor, Communication, Cognitive |
| Merrill-Palmer Revised | 1 month to 6 years 6 months | 30−40 min | Cognitive, Fine Motor, Receptive Language, Memory, Visual-Motor, Speed of Processing, Expressive Language, Gross Motor, Social-Emotional, Self-Help/Adaptive Temperament |
| Alberta Infant Motor Scale | Birth to 18 months | 20−30 min | Gross Motor Skills (assessed in four postures) |
| Peabody Developmental Motor Scales, 2nd edn. | Birth to 5 years 11 months | 45−60 min | Gross and Fine Motor |
Main Items of Clinical Neurological Assessment
- Systematic History Taking
- Pregnancy/birth details
- Milestones achieved
- Behavioral patterns
- Health/medications history
- Parental concerns
- Family history
- Physical Examination
- Growth and head circumference
- General physical health and development patterns
- Neurological Examination (e.g., Dubowitz method)
- Orientation/behavior (visual/auditory responses, consolability)
- Tone and posture evaluation
- Reflexes (Moro, grasp, placing)
- Movement quality and quantity
- Abnormal signs (tremors, posturing)
- Hammersmith Infant Neurological Examination (HINE)
- Assessment of cranial nerves, posture, spontaneous movements, muscle tone, reflexes/protective reactions.
👉 see also Hammersmith Infant Neurological Examination (HINE)
General Movement (GM) Assessment (Prechtl’s Method)
- Observational method to assess infant spontaneous movements.
- Predictive value for cerebral palsy and other developmental disorders.
- Writhing (9−49 weeks post-menstrual) and Fidgety (46−64 weeks) movements assessed.
- Cramped-synchronized and absent fidgety movements highly predictive of cerebral palsy.
👉 see also General Movement Assessment
Practical Conclusions
- Neurological clinical examination remains crucial despite advances in imaging/genetics.
- Examiners must distinguish between typical variability and abnormal development.
- Standardized assessments and comprehensive evaluations are crucial for accurate diagnosis and interventions.
- Repeated assessments provide developmental trajectories, essential for diagnosis, reassurance, and treatment planning.
