Write a short note on Anterior Fontanelle — Clinical Importance.

Anatomy

• The anterior fontanelle is the diamond-shaped membranous gap at the junction of the two frontal and two parietal bones (where the coronal and sagittal sutures meet).
• It is the largest of the six fontanelles and an important clinical 'window' in infancy.

Normal Facts

• Size at birth ~2.5 cm (diagonal); normally flat and pulsatile.
• Normally closes by 9–18 months (the posterior fontanelle closes by 6–8 weeks).
• Allows moulding of the head during birth and accommodates rapid brain growth in infancy.

Examination Technique

Palpate with the infant calm and held upright (crying or lying flat transiently makes it bulge). Assess tension, size and pulsation; a bulging non-pulsatile fontanelle is more concerning.

Bulging (tense) Fontanelle

• Raised intracranial pressure — meningitis, encephalitis, intracranial haemorrhage, tumour.
• Hydrocephalus; benign intracranial hypertension; hypervitaminosis A; lead encephalopathy.

Depressed (sunken) Fontanelle

• Dehydration (a key clinical sign in infantile diarrhoea).
• Severe undernutrition / wasting.

Large / Delayed-closing Fontanelle

• Hypothyroidism, rickets, Down syndrome.
• Raised ICP / hydrocephalus; osteogenesis imperfecta; IUGR; prematurity; achondroplasia.

Early / Small Closure

• Microcephaly, craniosynostosis, hyperthyroidism.

Clinical Approach

• The fontanelle is examined as part of every infant assessment.
• Combine the finding with the head circumference, level of consciousness, and hydration status to localise the problem — e.g. A bulging fontanelle + fever + lethargy points to meningitis, whereas a sunken fontanelle + reduced skin turgor points to dehydration.