Volumetric analysis of cranial vault distraction for cephalocranial disproportion.

The purpose of this study was to provide an objective analysis and quantify the intracranial volume change produced by cranial vault distraction osteogenesis. We recently published a technique to expand the cranial vault by distraction in symptomatic patients with findings of cephalocranial disproportion. Resolution of symptoms was documented in that publication. In this current study, we analyzed postdistraction intracranial volume changes in 11 consecutive patients retrospectively from 10/2001 to 11/2010 with institutional review board approval. These 11 patients were treated by cranial vault distraction osteogenesis for symptomatic cephalocranial disproportion. Pre- and postoperative CT DICOM data were analyzed using specialized software to generate finite element models. Intracranial and ventricular volumes were calculated. Topographical surface maps were generated to document and quantify areas of change. Possible effects on brain physiology are discussed. Pre- and postoperative CT scans were obtained at an average of 3.5 months prior to, and 4.2 months following distraction, respectively. Average age at distraction was 55.72 months (range 26-104 months). Operative time averaged 2 h 44 min (range 127-198 min, SD = 30.6). Intracranial and ventricular volumes increased by an average of 77.01 and 4.85 ml, respectively. Nonventricular intracranial volumes increased by 5.91%, 71.67 ml following distraction. All postoperative volume changes were statistically significant (p ≤ 0.000025). The ability to use the same methodology to quantify ventricular volume changes was unexpected. The fact that all ventricles expanded after distraction at approximately 10% of the total intracranial volume increase indicates that compensatory mechanisms had been activated. We conclude that this occurs at the expense of cerebral blood flow.