ULTRASONIC PRENATAL-DIAGNOSIS OF CORONAL SUTURE SYNOSTOSIS

The present study was designed to assess the utility and validity of s tandard prenatal ultrasonography in identifying individuals with coron al suture synostosis by examining sutural abnormalities before the dev elopment 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 Zea land White rabbits with simple, nonsyndromic craniosynostosis. Each mo ther was sedated with general anesthesia, and the gravid uterine hems were exposed via a laparotomy procedure. The fetal calvariae were exam ined using a no. 7 transducer at 7.0 mHz. Each coronal suture was scan ned using ultrasonography by first identifying bregma (the anterior fo ntanelle) al the intersection of the sagittal, interfrontal, and coron al 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 a s it progressed laterally. This finding is in accordance with the natu ral history of the synostotic foci and coronal suture fusion progressi on in these rabbits. In addition, the sagittal and interfrontal suture s in each synostotic rabbit appeared wider along their course compared with normal. This reflects early enhanced compensatory transverse gro wth resulting from the anteroposterior growth restrictions from corona l suture fusion. No other cranial shape abnormalities were recognizabl e at this stage of fetal development. The validity of the ultrasound d iagnoses was tested by direct ex utero inspection of 9 of the 17 synos totic fetuses. Gross morphological examination showed that 8 of 9 rabb it fetuses (89%) had fused coronal sutures, Statistical analysis revea led no significant difference (chi(2) = 0.22 P > 0.05) between the dia gnostic accuracy of standard ultrasonography and direct examination. I n conclusion, we have shown that standard ultrasonography of the calva rial sutures, in the absence of other craniofacial malformations, may he a feasible method of diagnosing simple, nonsyndromic craniosynostos is in utero, a condition that is typically missed during routine prena tal ultrasonic screening examinations.