What is the sensitivity of Transcranial Ultrasound (TCUS) in craniosynostosis?

Sensitivity of Transcranial Ultrasound (TCUS) in Craniosynostosis

Transcranial ultrasound has a high sensitivity ranging from 71% to 100% for diagnosing craniosynostosis in infants under 12 months of age, with most studies reporting sensitivity values above 90% and specificity between 86% and 100%. 1

Diagnostic Accuracy of TCUS in Craniosynostosis

TCUS has emerged as an excellent first-line imaging modality for evaluating cranial sutures in infants with suspected craniosynostosis. The evidence demonstrates:

• Sensitivity ranges from 71% to 100% across studies, with most reporting values above 90% 1
• Specificity is consistently high, ranging from 86% to 100% 1, 2
• In a prospective study of 126 children, TCUS demonstrated 100% sensitivity and 98% specificity for detecting craniosynostosis 2
• Another study of 196 infants confirmed high diagnostic accuracy with only two false positives reported during the initial learning phase 3

Advantages of TCUS Over Other Imaging Modalities

TCUS offers several advantages as a first-line imaging tool:

• Non-ionizing radiation technique, unlike skull radiographs and CT scans 2, 4
• No sedation required 4
• Rapid acquisition time 4
• Can be performed portably even on unstable infants 5
• Cost-effective screening tool 3

Technical Considerations and Limitations

The accuracy of TCUS depends on several factors:

• Age limitation: Best results are obtained in infants under 6 months of age, with decreasing utility as fontanels close 3
• Operator dependence: There is a learning curve, and the technique requires experienced ultrasonographers 3
• Suture-specific accuracy: Some studies report challenges in accurately assessing the metopic suture compared to other sutures 2
• Technical aspects: High-frequency linear transducers (7-12 MHz) provide optimal visualization of cranial sutures 4

Clinical Algorithm for Suspected Craniosynostosis

1. For infants under 12 months with suspected craniosynostosis, TCUS should be the first-line imaging modality
2. If TCUS shows normal patent sutures, further imaging can be avoided, and clinical follow-up is appropriate 4, 3
3. If TCUS confirms craniosynostosis, proceed to CT scan for surgical planning 4
4. For inconclusive TCUS results or infants older than 12 months, proceed directly to CT scan 3

Emerging Applications

Recent research has explored additional applications:

• Prenatal diagnosis of craniosynostosis using ultrasound, though this requires formal shape analysis rather than visual inspection or cephalic index alone 6
• Quantitative shape analysis of cranial contours can improve diagnostic accuracy 6

Common Pitfalls and Caveats

• TCUS is less sensitive for detecting craniosynostosis in infants older than 12 months due to natural narrowing of sutures 3
• The metopic suture may be more challenging to assess accurately, with some studies reporting disagreement between readers 2
• Case centralization is advisable due to the operator-dependent nature of the technique 3
• TCUS should be performed and interpreted by experienced radiologists familiar with normal suture appearance at different ages 3

In conclusion, TCUS represents a highly sensitive and specific first-line imaging modality for diagnosing craniosynostosis in infants under 12 months of age, allowing for reduction in unnecessary radiation exposure while maintaining excellent diagnostic accuracy.