Ultrasonic prenatal diagnosis of coronal suture synostosis

Abstract

The present study was designed to assess the utility and validity of standard prenatal ultrasonography in identifying individuals with coronal suture synostosis by examining sutural abnormalities before the development of secondary craniofacial dysmorphologies. An Accusson 128 XP ultrasound machine was used to scan the coronal sutures of 31 twenty-five-day-old fetuses (term = 31 days) from four timed-pregnant New Zealand White rabbits with simple, nonsyndromic craniosynostosis. Each mother was sedated with general anesthesia, and the gravid uterine horns were exposed via a laparotomy procedure. The fetal calvariae were examined using a no. 7 transducer at 7.0 mHz. Each coronal suture was scanned using ultrasonography by first identifying bregma (the anterior fontanelle) at the intersection of the sagittal, interfrontal, and coronal sutures and then following the coronal sutures laterally. Seventeen of the 31 fetuses were diagnosed with unilateral or bilateral coronal suture fusion. In fetuses with synostosis, the suture was echolucent and patent in the midline but then rapidly tapered off to fused bone as it progressed laterally. This finding is in accordance with the natural history of the synostotic foci and coronal suture fusion progression in these rabbits. In addition, the sagittal and interfrontal sutures in each synostotic rabbit appeared wider along their course compared with normal. This reflects early enhanced compensatory transverse growth resulting from the anteroposterior growth restrictions from coronal suture fusion. No other cranial shape abnormalities were recognizable at this stage of fetal development. The validity of the ultrasound diagnoses was tested by direct ex utero inspection of 9 of the 17 synostotic fetuses. Gross morphological examination showed that 8 of 9 rabbit fetuses (89%) had fused coronal sutures. Statistical analysis revealed no significant difference (chi 2 = 0.22, P > 0.05) between the diagnostic accuracy of standard ultrasonography and direct examination. In conclusion, we have shown that standard ultrasonography of the calvarial sutures, in the absence of other craniofacial malformations, may be a feasible method of diagnosing simple, nonsyndromic craniosynostosis in utero, a condition that is typically missed during routine prenatal ultrasonic screening examinations.