INTRACRANIAL VOLUME IN CRANIOSYNOSTOTIC RABBITS

Although craniosynostosis alters brain growth direction resulting in c ompensatory changes in the neurocranium, it has been suggested that su ch compensations occur with little reduction in intracranial volume (I CV). This hypothesis was tested in a rabbit model with nonsyndromic, f amilial coronal suture synostosis. Cross-sectional three-dimensional c omputed tomographic head scans were obtained from 79 rabbits (25 norma l, 28 with delayed-onset synostosis, and 26 with early-onset synostosi s) at 25, 42, and 126 days of age. Intracranial contents were reconstr ucted and indirect ICV was calculated. Results revealed that by 25 day s of age the intracranial contents from early-onset synostosed rabbit skulls showed rostral (anterior) constrictions and a ''beaten copper'' morphology in the parietal and temporal regions compared with the oth er two groups. These deformities increased in severity with age. Quant itatively, ICV was significantly reduced (p < 0.05) by 7% in rabbits w ith early-onset synostosis compared with both control rabbits and rabb its with delayed-onset synostosis at 25 days of age. By 126 days of ag e, ICV in rabbits with synostosis was significantly reduced (p < 0.05) by 11% in early-onset synostosis and by 8% in delayed-onset synostosi s compared with normal rabbits. Results suggest that in rabbits with u ncorrected craniosynostosis, compensatory changes in the neurocranium were not adequate to allow normal expansion of the neurocapsular matri x. Further research is needed to determine if ICV reduction is correla ted with cerebral atrophy or cerebral spinal fluid (i.e., ventricular or subarachnoid) space compression in this model.