Prenatal Diagnosis of Craniosynostosis Using Ultrasound

Background: Craniosynostosis is rarely diagnosed in utero , but rather postnatally through clinical exam and radiographic findings. Prenatal diagnosis would allow for improved parental counseling and facilitate timely intervention. The authors’ purpose is to determine if prenatal ultrasound can be used to diagnose nonsyndromic craniosynostosis, by quantitatively comparing calvarial dimensions of fetuses with known craniosynostosis, to age-matched controls. Methods: The authors reviewed 22 prenatal ultrasounds of infants known to have nonsyndromic craniosynostosis and 22 age matched controls. Cross sectional images at the plane used to measure biparietal diameter (BPD) were selected, and cranial shape of each subject was parameterized with a radial spoke model. Cephalic indices were calculated from the cross-sectional ultrasound images for cases of sagittal synostosis and compared to age-matched controls without craniosynostosis. We used the radial parameterization to discriminate affected patients from controls. The results from quantitative shape analysis were compared to results from a blinded visual inspection of ultrasound images conducted by the two senior authors (SRS, HOT). Results: Among the 22 patients, the most common diagnosis was sagittal synostosis (11), followed by metopic synostosis (6). The average gestational age at time of ultrasound of both controls and synostotic patients was 26 weeks and 6.8 days, at the junction of the second and third trimesters. The controls and synostotic cases segregated into statistically different populations by their shape profiles (P<0.001). An automatic shape classifier using leave-one-out cross validation correctly classified the 44 images as normals vs. synostotic cases 85% of the time (sensitivity 82%, specificity 87%). Cephalic index was a poor indicator of sagittal synostosis (45% sensitivity). Visual inspection alone demonstrated only a fair level of accuracy (40-50% agreement) in identifying cases of synostosis (kappa 0.09-0.23). Conclusions: Cases of craniosynostosis can be identified on prenatal ultrasound with good sensitivity using formal shape analysis. Cephalic index and visual inspection alone performed poorly in identifying cases of craniosynostosis. CLINICAL QUESTION/LEVEL OF EVIDENCE: Diagnostic, II.