Pediatric Neuroradiology

Pediatric Neuro: Dev & Congenital - Brain Blueprints

• Neurulation (3-4 wks): Neural tube forms. Defects:
  • Anencephaly: Absent cerebrum/vault, "frog-eye" sign.
  • Encephalocele: Cranial content herniation, occipital common.
  • Spina Bifida: Often with Chiari II malformation.
• Prosencephalic Development (5 wks): Forebrain cleavage. Defect:
  • Holoprosencephaly (HPE): Alobar, semilobar, lobar. Facial anomalies common. ⭐ > Holoprosencephaly is strongly associated with maternal diabetes and Patau syndrome (Trisomy 13).
• Neuronal Migration (8-20 wks): Neurons travel to cortex. Defects:
  • Lissencephaly: Smooth brain (agyria-pachygyria), "figure-8" MRI.
  • Heterotopia: Ectopic gray matter.
• Organization (20 wks - postnatal): Cortical folding & layering. Defects:
  • Polymicrogyria: Many small, disorganized gyri.
  • Schizencephaly: Gray matter-lined CSF clefts.
• Myelination (Birth - ~2 yrs): Pattern: Caudal→cranial, posterior→anterior, central→peripheral.
  • MRI: T1W ↑ (hyperintense), T2W ↓ (hypointense) with maturation.
  • Posterior Limb Internal Capsule (PLIC) myelinated by 7 months. Largely complete by 2 years.

Pediatric Neuro: HIE & Infections - Brain Battles

• Hypoxic-Ischemic Encephalopathy (HIE): Brain injury from O₂ deprivation.
  • Term Infants:
    • Pattern: Deep gray matter (basal ganglia, thalami), brainstem, perirolandic cortex, watershed zones.
    • MRI: Early DWI changes (within 24-48 hrs), later T1 hyperintensity. MRS: ↑Lactate, ↓NAA.
  • Preterm Infants:
    • Pattern: Periventricular Leukomalacia (PVL) - white matter injury, esp. near trigones.
    • MRI: Cystic changes, gliosis.
• Infections:
  • TORCH (Transplacental):
    • CMV: Most common. Periventricular calcifications, ventriculomegaly, polymicrogyria, white matter abnormalities.
    • Toxoplasmosis: Diffuse/basal ganglia calcifications, hydrocephalus, chorioretinitis (classic triad with convulsions).
    • HSV: Hemorrhagic necrosis (temporal/frontal lobes), diffusion restriction early.
  • Bacterial Meningitis:
    • Complications: Hydrocephalus (communicating/obstructive), infarcts (vasculitis), empyema, ventriculitis, abscess.
    • MRI: Leptomeningeal enhancement, DWI for pus/infarcts.

⭐ CMV is the most common congenital infection causing brain abnormalities, classically presenting with periventricular calcifications and migrational defects like polymicrogyria.

Pediatric Neuro: Tumors - Tiny Tumors, Big Trouble

• General: Infratentorial common (childhood); supratentorial (infancy/adolescence).
• Medulloblastoma (PNET):
  • Malignant. Cerebellar vermis. 📌 Malignant, Midline, Metastasis (CSF).
  • Imaging: Hyperdense CT, restricted diffusion MRI, avid enhancement.
• Pilocytic Astrocytoma (WHO I):
  • Most common benign. Cerebellum, optic pathway.
  • Cystic with enhancing mural nodule ("cyst with a dot"). Rosenthal fibers.
• Ependymoma:
  • 4th ventricle common. "Plastic tumor" - extends via foramina. Calcification (~50%).
• Craniopharyngioma:
  • Suprasellar. Adamantinomatous (children): cystic, lobulated, calcification (90%), "machine oil".
• Germ Cell Tumors:
  • Pineal (boys) or suprasellar. Germinoma (radiosensitive); Non-germinomatous (↑AFP/β-hCG).

⭐ Infratentorial tumors are more common than supratentorial tumors in children (approx. 2:1 ratio), reversing in adulthood. ``

Pediatric Neuro: Syndromes & Trauma - Skin & Skull Signs

• Neurocutaneous Syndromes (Phakomatoses):
  • NF-1: Café-au-lait spots, axillary freckling, Lisch nodules. Skull: Sphenoid wing dysplasia, lambdoid suture defects.
  • TSC: Ash-leaf spots (hypopigmented), facial angiofibromas, shagreen patch. Skull: Cortical/subependymal tubers (calcify), sclerotic lesions.
  • Sturge-Weber Syndrome (SWS): Port-wine stain (facial nevus flammeus, V1 distribution). Skull: Gyriform cortical calcifications ("tram-track").

    ⭐ Sturge-Weber Syndrome: Unilateral facial port-wine stain (V1/V2), ipsilateral leptomeningeal angiomatosis, glaucoma. "Tram-track" gyriform calcifications on CT are pathognomonic.

  • Encephalocraniocutaneous Lipomatosis (ECCL): Scalp lipomas, alopecia. Skull: Cranial asymmetry, intracranial lipomas.
• Pediatric Head Trauma - Skull Signs:
  • Fractures: Linear, depressed, diastatic (suture separation > 2-3 mm), growing skull fracture (leptomeningeal cyst).
  • Cephalohematoma: Subperiosteal, does not cross suture lines; may calcify.
  • Caput Succedaneum: Subcutaneous edema, crosses suture lines; resolves quickly.
• Other Skull Findings:
  • Craniosynostosis: Premature suture fusion (e.g., Apert, Crouzon syndromes).
  • Wormian bones: Intrasutural bones (e.g., osteogenesis imperfecta, cleidocranial dysostosis).

High‑Yield Points - ⚡ Biggest Takeaways

• Medulloblastoma: Most common malignant pediatric brain tumor, typically posterior fossa.
• Hypoxic-Ischemic Encephalopathy (HIE): Term infants - basal ganglia/thalamus; Preterm - periventricular white matter.
• TORCH infections: CMV - periventricular calcifications; Toxoplasmosis - diffuse calcifications.
• Chiari II malformation is almost always associated with myelomeningocele.
• Neurofibromatosis Type 1 (NF1): Characterized by optic pathway gliomas and UBOs.
• Tuberous Sclerosis Complex (TSC): Presents with cortical tubers, subependymal nodules, and SEGAs.
• Dandy-Walker malformation: Key features are cystic dilation of 4th ventricle and vermian hypoplasia.