II. Definitions

  1. Fontanelle size measurement
    1. Obtain anteroposterior diameter (AP)
    2. Obtain transverse diameter (T)
    3. Size = (AP + T) / 2
  2. Anterior Fontanelle
    1. Junction of coronal Suture and sagittal Suture
    2. Mean newborn size: 2.1 cm (larger in black infants) and may range up to 3-6 cm diameter
    3. Often enlarges in first few months of life
    4. Closes between 4 to 26 months (median 13.8 months)
    5. Closes by 3 months in 1% of infants
    6. Closes by 24 months in 96% of infants
  3. Posterior Fontanelle
    1. Junction of lambdoidal Suture and sagittal Suture
    2. Mean newborn size: 0.5 to 0.7 cm and may range up to 1 to 1.5 cm
    3. Closes by 2 months

III. Exam: Anterior Fontanelle

  1. Palpate Fontanelle with infant sitting upright quietly
    1. Fontanelle should feel soft
    2. Fontanelle should not be sunken or bulging
  2. Other examination features
    1. Auscultate for bruit (suggests AV malformation)
    2. Macewen's Sign (percussion of Fontanelle)
      1. Dull cracked-pot sound suggests increased ICP

IV. Causes: Abnormal Anterior Fontanelle

  1. Bulging Fontanelle causes
    1. Crying, coughing or Vomiting
    2. Increased Intracranial Pressure
      1. Hydrocephalus
      2. Meningitis or Encephalitis
      3. Hypoxic-ischemic injury
      4. Trauma
      5. Intracranial Hemorrhage
      6. Dermoid tumors of the scalp
  2. Sunken Fontanelle causes
    1. Decreased Intracranial Pressure (dehydration)
  3. Large Fontanelle or delayed closure
    1. Congenital Hypothyroidism
    2. Trisomy 21 (Down Syndrome)
    3. Rickets (with Hypophosphatemia)
    4. Achondroplasia
    5. Increased Intracranial Pressure
  4. Small Fontanelle or early closure
    1. Early closure may be normal
    2. Always evaluate for Microcephaly
    3. Craniosynostosis

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Ontology: Structure of fontanel of skull (C0224548)

Definition (NCI) The four gaps in the skull of a neonate or fetus where the sutures converge. The bulging or depression of the membranous soft spots can be indicative of intracranial fluid buildup or systemic dehydration.
Concepts Body Space or Junction (T030)
SnomedCT 79361005
English Fontanelles, Set of fontanelles, Fontanelle, Fontanelles set, Fonticulus cranii, fontanelles, fontanelle, Fontanel of skull, Structure of fontanel of skull (body structure), Structure of fontanel of skull, Fontanel of skull, NOS
Spanish estructura de la fontanela del cráneo (estructura corporal), estructura de la fontanela del cráneo, fontanela del cráneo

Ontology: Structure of anterior fontanel of skull (C0224549)

Concepts Body Space or Junction (T030)
MSH D055762
SnomedCT 77564006
English AF - anterior fontanelle, Anterior fontanelle, Fonticulus anterior, Fontanelles, Anterior, Fontanel, Anterior, Fontanelle, Anterior, Anterior Fontanelle, Anterior Fontanels, Anterior Fontanelles, Anterior Fontanel, Fontanels, Anterior, anterior fontanelle, Anterior fontanel of skull, Structure of anterior fontanel of skull (body structure), Structure of anterior fontanel of skull
French Fontanelle antérieure
German Vordere Fontanelle
Czech fonticulus anterior, fonticulus major, čtyřcípý velký lupínek
Norwegian Fremre fontanelle, Pannefontanelle, Fonticulus anterior, Store fontanelle
Spanish estructura de la fontanela anterior del cráneo (estructura corporal), estructura de la fontanela anterior del cráneo, fontanela anterior del cráneo