Fontanelle
- 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)
- 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
- 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 of 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 hypothyroid
- trisomy 21
- rickets
- achondroplasia
- increased icp
- Small fontanelle or early closure
- Early closure may be normal
- Always evaluate for microcephaly
- craniosynostosis