Single most likely diagnosis
- Craniosynostosis: This condition involves the premature closure of the cranial sutures, which can lead to a small anterior fontanelle. It is a common cause of this finding in neonates.
Other Likely diagnoses
- Deformational plagiocephaly: This condition occurs when the head is consistently in one position, causing the bones to shift and potentially leading to a smaller fontanelle.
- Intrauterine growth restriction (IUGR): Babies with IUGR may have smaller fontanelles due to restricted growth and development.
- Premature closure of the metopic suture: This can also result in a smaller anterior fontanelle.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Cranial bone disorders (e.g., osteopetrosis, craniodiaphyseal dysplasia): These rare conditions can lead to abnormal bone growth and small fontanelles, and are critical to diagnose due to potential complications.
- Meningoencephalocele or other neural tube defects: Although less common, these conditions can cause a small fontanelle and require prompt diagnosis and treatment.
Rare diagnoses
- Apert syndrome: A rare genetic disorder characterized by craniosynostosis and other abnormalities.
- Crouzon syndrome: Another rare genetic disorder involving craniosynostosis and facial abnormalities.
- Other rare genetic syndromes (e.g., Pfeiffer syndrome, Saethre-Chotzen syndrome): These conditions often involve craniosynostosis and other distinctive features.