Development of a Strain of Rabbits with Congenital Simple Nonsyndromic Coronal Suture Synostosis Part II: Somatic and Craniofacial Growth Patterns

Abstract

In the March 1993 issue of The Cleft Palate-Craniofacial Journal we reported a female rabbit born in our laboratory with complete bilateral coronal suture (CS) synostosis. This follow-up study presents our attempts to breed the animal and establish a strain of craniosynostotic rabbits. The second part of this study presents longitudinal somatic and craniofacial growth data in offspring with coronal suture synostosis. Serial growth data from 72 animals were collected for the present study. The sample consisted of 11 animals (10 offspring and the original female) with complete nonsyndromic unilateral (plagiocephalic) or bilateral (brachycephalic) CS synostosis, 19 animals with partial CS synostosis, and 42 unaffected control litter mates. At 10 days of age, all animals had radiopaque amalgam markers placed on either side of the frontonasal, coronal, anterior lambdoidal, and sagittal sutures. Body weights and serial lateral and dorsoventral head radiographs were taken at 1.5 (10 days), 6, 12, and 18 weeks of age. All animals showed similar body weights at 1.5 weeks of age, while completely synostosed animals exhibited a slight (about 12%), but significantly (p < .001) lowered body weight by 18 weeks of age. Results revealed that by 1.5 weeks of age the completely synostosed animals already exhibited brachycephalic cranial vaults, mid-facial hypoplasia, and increased flattening of the cranial base compared to unaffected siblings. This pattern continued through 18 weeks of age, with the partially synostosed animals exhibiting Intermediate morphologies. Compensatory overgrowths were noted primarily at the sagittal and frontonasal sutures, especially for completely synostosed animals. Findings revealed that the craniosynostotic rabbits followed predictable compensatory craniofacial growth patterns and exhibited secondary deformities similar to those reported for cases of human coronal suture synostosis. Such findings support continued efforts at developing this model to help understand, In part, the etiopathogenesis of this condition in human populations.