What is the role of transcranial ultrasound (US) in the diagnosis and treatment of craniosynostosis?

Role of Transcranial Ultrasound in Craniosynostosis

Transcranial ultrasound (TCUS) should be used as the first-line imaging modality for suspected craniosynostosis in infants under 12 months of age, as it provides sufficient diagnostic information with no radiation exposure. 1

Advantages of Transcranial Ultrasound in Craniosynostosis

• No radiation exposure: Unlike CT scans which expose infants to ionizing radiation
• High diagnostic accuracy: Multiple studies show sensitivity and specificity approaching 100% for detecting suture closure 2, 3
• Cost-effective: Less expensive than CT or MRI
• No sedation required: Can be performed quickly without the need for sedation
• Real-time imaging: Allows direct visualization of cranial sutures and fontanelles
• Bedside availability: Can be performed at the bedside for unstable infants 4

Diagnostic Algorithm for Suspected Craniosynostosis

1. Initial evaluation: Clinical assessment of head shape, palpation of sutures, and fontanelle examination

2. First-line imaging: TCUS for infants younger than 12 months (optimal results under 6 months) 1, 2

3. TCUS findings interpretation:

   • Negative TCUS: No further imaging needed; clinical follow-up and potential physical therapy for positional plagiocephaly 2, 5
   • Positive TCUS: Referral to neurosurgery
   • Inconclusive TCUS: Proceed to CT or MRI

4. Advanced imaging indications:

   • Surgical planning
   • Complex or syndromic craniosynostosis
   • Evaluation of intracranial complications
   • Children older than 12 months where TCUS is less reliable 1

Evidence Supporting TCUS Use

Studies consistently demonstrate excellent correlation between TCUS and 3D-CT findings. In a cohort of 196 infants with suspected craniosynostosis, TCUS showed high diagnostic accuracy with only two false positives in the early learning phase 2. Another study of 40 infants found 100% sensitivity and specificity when comparing TCUS to 3D-CT 3.

Limitations and Considerations

• Operator dependence: TCUS accuracy depends on the sonographer's experience and expertise 2
• Age limitation: Most effective in infants younger than 8-12 months 6
• Learning curve: Requires training and experience to achieve optimal results
• Visualization challenges: Some sutures may be more difficult to visualize than others

Radiation Risk Reduction

Avoiding unnecessary CT scans is particularly important in young infants. One study demonstrated that in 97.1% of 137 infants with suspected single-suture craniosynostosis, diagnosis was achieved through clinical examination alone, with only rare need for additional imaging 5. When imaging is needed, TCUS should be the first choice to avoid radiation exposure.

When to Use Other Imaging Modalities

• CT scan: Reserved for surgical planning or when TCUS is inconclusive 1
• MRI with black bone sequence: Preferred for evaluation of suspected intracranial hypertension 1
• Plain radiographs: May be postponed until the date of surgery or the end of the first year 5

By implementing TCUS as the first-line imaging modality for suspected craniosynostosis in infants, clinicians can achieve accurate diagnosis while minimizing radiation exposure and avoiding unnecessary advanced imaging.