Coronal Suture Fusion Research Articles

A new in utero sheep model for unilateral coronal craniosynostosis.

Several animal models have been designed in the past to analyze the pathophysiology and management of craniosynostosis, very few of which were intrauterine. Those that were interuterine had problems with either a short gestation or limited availability that prevented most researchers from using them in treatment analysis. We desired to create a biologically sound intrauterine model of craniosynostosis, using an animal with a long gestation and an early calvarial bone formation, which was easy to manipulate in utero, that could be created by any researcher studying this disorder. Using biologic data available regarding growth factors thought to be involved in bone growth and cranial suture closure, we developed a new in utero fetal lamb model for the study of craniosynostosis. Ten 70-day gestation fetal lambs (term gestation 140 days) received a midline coronal incision to expose both coronal sutures. The entire right coronal suture was then excised along with a 4-mm bony margin. In each animal, the site was packed with 25 mg of demineralized sheep bone powder augmented with 50 microg of bone morphogenetic protein-2 (BMP-2) and 1 microg of poly-transforming growth factor-beta. The scalp was closed, and the sheep were returned to the uterus until either 90 or 140 days of gestation. Complete fusion of the right coronal suture occurred in all fetuses by 90 days gestation. In every animal, right-sided frontal bone flattening and supraorbital rim elevation were evident. Histologic analysis showed bony synostosis at the suture site without evidence of suture regeneration. By 140 days, this isolated suture fusion led to marked craniofacial abnormalities including right supraorbital rim elevation, significant frontal bone flattening, a decrease in the anterior-posterior length of the cranial vault, and flattening of the cranial base. In conclusion, we have developed a new model for the study of the secondary effects induced by the process of cranial suture fusion, which produces abnormalities seen in naturally occurring cases of isolated right coronal suture synostosis. In addition, this model confirms that isolated coronal suture fusion alone can lead to the multiple cranial and facial abnormalities seen with this disorder, even in the absence of associated cranial base suture fusions.

Ultrasonic prenatal diagnosis of coronal suture synostosis.

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.

Iron-Induced Rat Coronal Suture Fusion In Vitro

The presumptive coronal sutures of rat fetuses at gestation days 19 and 20 have been shown to fuse prematurely when grown in the absence of dura mater in culture. In the present study, the representative enzymes of glucose metabolism and the antioxidative pathway were assayed during the process of suture fusion. The coronal sutures of fetal day 19.5 (F19) and neonatal day 1 rats were grown in the presence or absence of dura mater in serum-free culture. The enzymes assayed were hexokinase (HK) and pyruvate kinase (PK) of glycolysis, and glucose 6-phosphate dehydrogenase (G6PD) and glutathione reductase (GR) of the antioxidative pathway. F19 sutures cultured without dura mater, which fused, showed significant increases in enzyme activities over the preculture levels. HK increased by 200% to 300% of the preculture levels, G6PD by 400% to 500%, GR by 200%, and PK by 400% to 500%. The fetal sutures cultured with dura mater, which did not fuse, showed little alterations of HK, G6PD, and GR activities, but showed a significant 200% to 400% increase in PK activity. Neonatal sutures showed significant increases in enzyme activities during culture, but the presence of dura mater did not significantly affect enzyme activities. High activity levels of enzymes of the antioxidative pathway in F19 sutures coincided with the period of premature suture fusion. Treatment of fetal calvaria with prooxidant (induced by ferrous iron and ascorbic acid) produced suture fusion even in the presence of dura mater. Treatment with deferoxamine (an iron chelator and antioxidant) during the culture prevented suture fusion. The results suggest that fusing sutures experience increased biosynthetic demands and are placed under oxidative stress. When oxidative stress overwhelms the dural influence, the sutures undergo premature fusion.

Prolonged General Anesthesia for Experimental Craniofacial Surgery in Fetal Swine

A protocol utilizing high preoperative doses of altrenogest (Regu-Mate) and a “balanced” general anesthesia regimen consisting of isoflurane at subanesthetic doses supplemented with intravenous doses of sodium thiopental was developed to prevent preterm labor, minimize intracranial fetal cerebral edema, and decrease post-partum mortality of fetal swine after undergoing complex in utero craniofacial procedures. A total of 20 fetal piglets at 75% gestation were exposed to prolonged (>3 h) anesthesia conditions of which 7 piglets were randomly selected to undergo experimental craniofacial procedures consisting of periosteal stripping of frontal and parietal bone segments with/without extensive coronal suture fusion procedures. Neither sows nor piglets were lost to anesthetic complications during the initial laparotomy or subsequent cesarean delivery. None of the sows experienced uterine sepsis or underwent preterm labor. The overall survival rate for all piglets exposed to prolonged anesthesia conditions was 95% at 4 weeks and 45% at 11 weeks after surgery. The experimental group's survival was 85.7% at 4 weeks and 28.5% at 11 weeks after surgery.

Surgical model to assess the effects and optimal timing of craniofacial fixation.

An in utero swine model of craniofacial deformity was developed as a potential alternative to neonatal models currently used for evaluating the optimal timing and long-term effects of rigid fixation techniques on a growing cranium. At 75% gestation, seven fetal piglets were randomly selected to undergo periosteal stripping of frontal and parietal bone segments with and without extensive coronal suture fusion procedures with cyanoacrylate adhesive. Fetal swine were killed postpartum at 4 and 11 weeks after fusion to assess craniofacial deformity. Piglets undergoing coronal fusion had slight deviation of the nose-snout toward the side of fusion and taller cranial vaults. The vertical cranial index of the experimental fusion group was 0.34 in comparison to a vertical index of 0.27 for the controls, suggesting abnormal vertical height expansion. There was no difference in the horizontal cranial index of either control or experimental fusion groups. Neither sows nor piglets were lost to anesthetic complications, uterine sepsis, or preterm labor during the initial laparotomy or subsequent cesarean delivery.