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Section 9 — Neurology Pending expert review v1.0 · July 2026

Chapter 9.8 — Developmental Neurology & the Neonatal Neurologic Examination: A Framework

Board-review synthesis · pending expert review

Educational guideline — verify locally. Provides an integrative framework complementing the condition-specific guidelines: HIE (9.1), IVH (9.2), seizures (9.3), PVL (9.4), stroke (9.5), hypotonia (9.6), neural tube defects (9.7). Cross-references those for management detail.

1. Clinical Overview

Clinical Overview

Neonatal neurology is developmental neurology: the brain is unfinished — still migrating neurons, building connections, and myelinating — so timing determines everything. Which malformation occurs, which region is vulnerable to injury at which gestation, why seizures look unlike those of older children, and why the examination must be read against maturity all follow from that immaturity. This framework ties the pieces together: date the malformation by stage, read the examination as a serial instrument interpreted against gestation, and localise problems (e.g., hypotonia along the neuraxis) before reaching for a differential.

2. Key Clinical Points

Key Clinical Points
  • Developmental stages date malformations: neurulation → neural tube defects (anencephaly, spina bifida); prosencephalic development → holoprosencephaly (+ midline facial anomalies), corpus callosum agenesis; proliferation → microcephaly; neuronal migration → lissencephaly, heterotopia, polymicrogyria.
  • Neural tube defects are largely preventable by PRECONCEPTIONAL folic acid (the tube closes before pregnancy is recognised); detectable prenatally (elevated maternal AFP, ultrasound); risk raised by maternal diabetes and some antiepileptics; spina bifida → high latex-allergy rate. Cover an open defect sterilely, prevent infection, arrange urgent closure, watch for hydrocephalus.
  • Hydrocephalus in the open-sutured newborn → rapidly enlarging head circumference, full/bulging fontanelle, splayed sutures, later sunsetting eyes; serial head circumference is a free screening tool — an upward-crossing centile demands imaging.
  • The neurologic examination is read against MATURITY: assess state first (alertness is the earliest, most sensitive sign of encephalopathy), then tone (flexion matures from the legs upward with gestation), then reflexes (asymmetry localises; persistence suggests cortical dysfunction). Its greatest value is serial repetition — the trend (improving/static/deteriorating) outweighs any single finding.
  • Imaging/EEG answer different questions: cranial ultrasound (bedside, screens preterm for IVH/ventricular dilatation/cystic injury); MRI (defines HIE pattern, stroke, subtle white-matter injury, malformations; prognostic — timed ~end of first week); EEG/aEEG (cortical function and electrographic seizures).
  • IVH originates in the germinal matrix (fragile vessels that involute by term) → a preterm disease with risk falling as gestation rises; the pressure-passive preterm brain transmits BP swings/hypercarbia to those vessels — so stable, gentle early care is neuroprotection. Grades track outcome; parenchymal 'grade IV' is a venous infarction, not simple extension.
  • Periventricular leukomalacia: watershed location + pressure-passive circulation + vulnerable pre-myelinating oligodendrocytes; inflammation is central (chorioamnionitis, sepsis, NEC) as well as ischaemia. Leg fibres run nearest the ventricle → classic spastic diplegia (legs>arms). Antenatal corticosteroids reduce IVH; maternal magnesium sulphate reduces cerebral palsy.
  • Neonatal seizures are usually acute-symptomatic (not epilepsy), subtle (eye deviation, lip-smacking, pedalling, apnea without early bradycardia), and frequently electrographic-only. Electroclinical uncoupling (worse after anticonvulsants) means EEG monitoring, not observation, guides therapy; correct metabolic causes first (glucose, then Ca/Na/Mg); treat electrographic as well as clinical seizures (burden adds injury); jitteriness stops when the limb is held (no eye deviation/autonomic change).
  • Hypotonia is solved by localisation: central (brain) = floppy but preserved strength, normal/brisk reflexes, depressed alertness ± seizures (HIE, trisomy 21, Prader-Willi, malformations, IEM, maternal magnesium); peripheral (motor unit) = floppy AND weak, reduced/absent reflexes, preserved alertness, ± wasting/fasciculations/contractures/respiratory weakness. An alert, weak, areflexic infant is peripheral until proven otherwise — SMA (anterior horn cell: tongue fasciculations, respiratory involvement) now has disease-modifying therapy and newborn screening in some regions.
  • Microcephaly: primary (brain never grew — genetic/chromosomal/proliferation disorders) vs acquired (grew then injured — severe HIE, congenital infection [CMV, Zika, toxoplasmosis]); the growth trajectory distinguishes them. Craniosynostosis (fused suture, palpable ridge, surgical) must be distinguished from positional plagiocephaly (open sutures, resolves with positioning).

3. References to Verify

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