Neonatology Book

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FontanelleAka: Fontanel, Anterior Fontanelle, Posterior Fontanelle

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  1. See Also
    1. Newborn Head and Neck Exam
    2. Newborn Neurologic Exam
    3. Head Circumference
    4. Craniosynostosis
  2. 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)
      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
      3. Closes by 2 months
  3. 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
  4. Causes of 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
      4. Achondroplasia
      5. Increased Intracranial Pressure
    4. Small fontanelle or early closure
      1. Early closure may be normal
      2. Always evaluate for Microcephaly
      3. See Craniosynostosis
  5. References
    1. Bates (1991) Physical Exam, Lippincott, p. 586
    2. Fuloria (2002) Am Fam Physician 65(1):61
    3. Kiesler (2003) Am Fam Physician 67(12):2547

Structure of fontanel of skull (C0224548)

ConceptsBody Space or Junction (T030)
EnglishFontanel of skull, Fontanelle, Fontanelles, Set of fontanelles, Structure of fontanel of skull
Spanishestructura de la fontanela del cráneo, estructura de la fontanela del craneo, fontanela del cráneo, fontanela del craneo
CreditsDerived from the NIH UMLS (Unified Medical Language System)


Structure of anterior fontanel of skull (C0224549)

ConceptsBody Space or Junction (T030)
EnglishAnterior fontanel of skull, Anterior fontanelle, Structure of anterior fontanel of skull
Spanishestructura de la fontanela anterior del cráneo, estructura de la fontanela anterior del craneo, fontanela anterior del cráneo, fontanela anterior del craneo
CreditsDerived from the NIH UMLS (Unified Medical Language System)



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