What is the name of the soft spot in a baby's head?

The Fontanelle: Understanding the "Soft Spot" in a Baby's Head

The soft spot in a baby's head is called the anterior fontanelle. This is a normal anatomical feature present at birth that allows for brain growth and facilitates passage through the birth canal 1.

Anatomy and Characteristics of the Anterior Fontanelle

• The anterior fontanelle is the largest of six fontanelles present at birth 2
• It is located at the junction between the frontal and parietal bones of the skull 1
• Average size at birth is approximately 2.1 cm 2
• Normal fontanelle feels firm but slightly soft to touch, neither bulging nor sunken
• The anterior fontanelle typically closes at a median age of 13.8 months 2

Clinical Significance

The anterior fontanelle serves as an important "window to the brain" and has significant diagnostic value:

• Size assessment: Normal width at birth is about 2.0 cm, decreasing to 0.6 cm by 12 months of age 3
• Closure timing: Boys tend to have slightly earlier closure than girls 3
• Pressure indicators:
  • Bulging fontanelle may indicate increased intracranial pressure
  • Sunken fontanelle often suggests dehydration 2

Abnormal Findings and Associated Conditions

Abnormalities of the anterior fontanelle may indicate underlying conditions:

• Large fontanelle or delayed closure may suggest:

  • Achondroplasia
  • Hypothyroidism
  • Down syndrome
  • Increased intracranial pressure
  • Rickets 2

• Bulging fontanelle may indicate:

  • Increased intracranial pressure
  • Intracranial or extracranial tumors
  • Hydrocephalus
  • Meningitis 2, 4

• Premature closure may suggest:

  • Craniosynostosis
  • Microcephaly

Examination Techniques

When examining the anterior fontanelle:

• Position the infant upright to minimize venous pressure effects
• Use gentle palpation to assess size, tension, and pulsations
• Measure both anterior-posterior and transverse diameters
• Note any associated findings like widened sutures or rapid head circumference growth 4

Imaging Considerations

If abnormalities are detected:

• Ultrasonography through the fontanelle can provide valuable brain imaging in infants 3
• CT or MRI may be indicated for suspected increased intracranial pressure or structural abnormalities 2
• Plain films may help identify craniosynostosis

Evolutionary Significance

The anterior fontanelle is considered a derived human feature that facilitates:

• Fetal head molding during birth
• Accommodation of rapid brain growth in early infancy 5

The anterior fontanelle's examination provides crucial information about an infant's neurological status and overall health, making it an essential component of pediatric assessment.