Macewen’s sign is a “cracked-pot” sound heard on light percussion over an infant’s or young child’s anterior fontanel, indicating increased intracranial pressure or abnormal cranial cavity expansion. It is an early clinical indicator of hydrocephalus and may also occur in cerebral abscesses.

Pathophysiology

Normal physiology:

• The anterior fontanel in infants is soft and compressible, with normal intracranial pressure allowing normal percussion sounds.

Abnormal physiology (hydrocephalus or cerebral abscess):

• Accumulation of cerebrospinal fluid or mass effect increases intracranial pressure, causing separation of cranial bones and tension at the sutures.

• Light percussion produces a resonant “cracked-pot” sound due to the air–fluid–bone interface and widened sutures.

• Early detection allows timely intervention before cranial deformity or neurological deficits occur.

Associated findings: May include rapid head growth, bulging fontanel, vomiting, irritability, or sunset eyes in hydrocephalus.

Examination Technique

• Patient positioning: Infant should be supine and calm, preferably gently restrained by a caregiver.

• Percussion: Using one finger, lightly percuss over the anterior fontanel.

• Observation: Listen for a “cracked-pot” or resonant metallic sound, suggesting increased intracranial pressure.

• Documentation: Record fontanel size, tension, percussion sound quality, and associated neurological or systemic findings.

Clinical Features

Differential Diagnosis

Special populations

Neonates and infants:

• Fontanel must still be open to elicit the sign; closed sutures prevent detection.

Premature infants:

• Smaller fontanels may make percussion more challenging; light touch is critical to avoid injury.

Limitations

• Requires open anterior fontanel, limiting use to infants and young children.

• Percussion is subjective, requiring clinical experience.

• Subtle cases may be missed, and sound may vary with fontanel size, thickness, and skull tension.

• Should always be interpreted alongside other clinical signs of raised intracranial pressure.

Patient counseling

• Explain that the sound indicates possible increased intracranial pressure or cranial abnormality.

• Advise urgent pediatric or neurosurgical evaluation for imaging (ultrasound, CT, or MRI).

• Monitor for head growth, vomiting, lethargy, or neurological changes, and report promptly.

Conclusion

Macewen’s sign is an early clinical indicator of hydrocephalus or cerebral abscess, detected as a “cracked-pot” sound over the anterior fontanel on light percussion. Recognition facilitates timely imaging, diagnosis, and intervention, potentially preventing neurological complications.

References

1. Macewen W. The diagnosis of hydrocephalus. Lancet. 1877;2:125–127.

2. Oakes WJ, Swanson JW. Hydrocephalus in children: Clinical features and management. Pediatr Clin North Am. 1992;39:253–267.

3. Swaiman KF, Ashwal S, Ferriero DM, Schor NF. Swaiman’s Pediatric Neurology. 6th ed. Philadelphia: Elsevier; 2017.

4. Albright AL, Pollack IF, Adelson PD. Principles and Practice of Pediatric Neurosurgery. 3rd ed. New York: Thieme; 2012.