Changes in orbital volume during childhood in cases of craniosynostosis.

OBJECT

Controversy remains concerning the timing of frontoorbital advancement (FOA) surgery performed for craniosynostosis. Reduced orbital volume and degree of exorbitism are often cited as reasons for early surgical intervention. To date, however, little attention has been given to orbital volume and its changes during the first few years of life as an indicator of orbital growth in children with craniosynostosis. Knowledge of orbital volume and growth patterns in individuals with craniosynostosis and those with normal cranial structures will enable surgeons to refine both the type and timing of surgical intervention required, thus obtaining the optimum outcome for their patients.

METHODS

Using the procedure of segmentation, orbital volumes in 50 children with various forms of craniosynostosis were measured on preoperative computerized tomography scans. Changes in average volume that occur with increasing age were calculated and compared with a model of normal orbital volume growth. At presentation the children with craniosynostosis ranged in age from 1 to 29 months, with 82% of them within the 1st year of life. Several interesting observations emerged from this study. Excluding patients with unilateral coronal synostosis, there was no difference between orbital volumes measured on the right and left sides, allowing mean orbital volume measurements to be used for comparative purposes. Although children with craniosynostosis begin life with significantly smaller orbital volumes, overall normal mean volumes for both sexes are attained by 13 months of age, with volumes approaching normal by 6 months of age in male infants and by 8 months of age in female infants. Changes in orbital volume associated with age generally appear to be similar in most forms of craniosynostosis. There appears to be no significant difference in changes in orbital volume between children with syndromic or nonsyndromic forms of bicoronal synostosis. Orbital volume is significantly reduced on the ipsilateral affected side in cases of unicoronal synostosis in comparison with the contalateral side, but it is not significantly lower than that of normal. Finally, FOA surgery appears to restore normal growth of orbital volume.

CONCLUSIONS

The results of this study indicate that the underlying mechanism leading to craniosynostosis and restriction of orbital volume "burns out" and begins to lose its major effects within the first few months of life. It would appear that FOA surgery should be delayed until the end of the second half of the 1st year of life, thus maximizing the effects of accelerated normal orbital growth and reducing the risks of relapse.