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Fontanelle
Aka: Fontanelle, Fontanel, Anterior Fontanelle, Posterior Fontanelle
- See Also
- Newborn Head and Neck Exam
- Newborn Neurologic Exam
- Head Circumference
- Craniosynostosis
- Definitions
- Fontanelle size measurement
- Obtain anteroposterior diameter (AP)
- Obtain transverse diameter (T)
- Size = (AP + T) / 2
- Anterior Fontanelle
- Junction of coronal Suture and sagittal Suture
- Mean newborn size: 2.1 cm (larger in black infants) and may range up to 3-6 cm diameter
- Often enlarges in first few months of life
- Closes between 4 to 26 months (median 13.8 months)
- Closes by 3 months in 1% of infants
- Closes by 24 months in 96% of infants
- Posterior Fontanelle
- Junction of lambdoidal Suture and sagittal Suture
- Mean newborn size: 0.5 to 0.7 cm and may range up to 1 to 1.5 cm
- Closes by 2 months
- Exam: Anterior Fontanelle
- Palpate Fontanelle with infant sitting upright quietly
- Fontanelle should feel soft
- Fontanelle should not be sunken or bulging
- Other examination features
- Auscultate for bruit (suggests AV malformation)
- Macewen's Sign (percussion of Fontanelle)
- Dull cracked-pot sound suggests increased ICP
- Causes: Abnormal Anterior Fontanelle
- Bulging Fontanelle causes
- Crying, coughing or Vomiting
- Increased Intracranial Pressure
- Hydrocephalus
- Meningitis or Encephalitis
- Hypoxic-ischemic injury
- Trauma
- Intracranial Hemorrhage
- Dermoid tumors of the scalp
- Sunken Fontanelle causes
- Decreased Intracranial Pressure (dehydration)
- Large Fontanelle or delayed closure
- Congenital Hypothyroidism
- Trisomy 21 (Down Syndrome)
- Rickets (with Hypophosphatemia)
- Achondroplasia
- Increased Intracranial Pressure
- Small Fontanelle or early closure
- Early closure may be normal
- Always evaluate for Microcephaly
- Craniosynostosis
- References
- Bates (1991) Physical Exam, Lippincott, p. 586
- Fuloria (2002) Am Fam Physician 65(1):61-8 [PubMed]
- Kiesler (2003) Am Fam Physician 67(12):2547-52 [PubMed]