Intracranial volume change in craniosynostosis

There is still controversy regarding the optimum time to perform surgery for craniosynostosis. Some recommend surgery soon after birth and others delay until the age of 12 months. Intracranial pressure has been measured in an attempt to provide a scientific rationale, but many questions remain unanswered. To date, little attention has been given to intracranial volume and its changes during the first few years of life in children with craniosynostosis. The authors' goal was to focus on intracranial volume during this period and to compare measurements obtained in patients with craniosynostosis with measurements obtained in healthy individuals.

Using the technique of segmentation, the intracranial volume of 84 children with various forms of craniosynostosis was measured on preoperative computerized tomography scans. The change in average volume that occurs with increasing age was calculated and compared with a model of normal intracranial volume growth. The age at presentation for children with craniosynostosis was 1 to 39 months; 76% of the patients were younger than 12 months. In eight patients in whom only one cranial expansion procedure was performed, postoperative intracranial volumes were measured as well. Several interesting observations emerged. 1) There was little difference in head growth between boys and girls with craniosynostosis during the first few months of life. After the age of 12 months, however, the difference in intracranial volume normally seen between the two genders was observed in the craniosynostosis group as well. 2) Excluding children with complex pansynostosis, who have smaller heads, children with all other types of craniosynostosis have similar head growth after the 1st year of life, with no difference between the number of and type of suture affected. Children with Apert's syndrome develop greater than normal intracranial volumes after the 1st year of life. 3) Although children with craniosynostosis are born with a smaller intracranial volume, by the age of 6 months volume has reached normal levels, and from that point on volume follows the pattern of normal head growth. 4) Children who presented after the age of 6 months and later developed recurrent craniosynostosis after initial successful treatment had a small intracranial volume at their initial presentation. 5) Of the patients whose postoperative intracranial volumes were measured, all but one had preoperative volumes at or above normal values, and their postoperative volumes were considerably higher than normal for their age. These children all followed a growth curve parallel to that of healthy children but at higher volume value. One patient with a smaller-than-normal initial intracranial volume was surgically treated at a very young age and, despite cranial expansion surgery, postoperative volume did not reach normal levels. It is postulated that this was due to the fact that the operation was performed at a time when craniosynostosis was still active.

The results of this study indicate that the underlying mechanism leading to craniosynostosis and constriction of head volume "exhausts" its effect during the first few months of life. Measurement of intracranial volume in clinical practice could be used to "fine tune" the optimum time for surgery. In late-presenting children, this may be useful in predicting possible recurrence.