Children with craniosynostosis almost universally have surgery to reopen the sutures and allow normal growth of the boney plates of the skull. Premature closure of sutures causes the skull and the brain beneath to deform. However, the researchers had few CT and MRI images to work with because even if both CT and MRI are acquired for a patient, they are rarely obtained the same day.
"We are extremely conservative in requiring that the two types of images be taken within a 24-hour period," says Richtsmeier. "Early brain and skull growth are so rapid that if the images were taken weeks apart, they would not be an exact fit." T scans record a three-dimensional image of the skull while MRIs provide a three-dimensional brain image.
The researchers caution that the number of infants studied in this way is small at this point, but they found that the brain and skull are strongly integrated.
"We also expected to see higher correlation among those brain and skull measures that were close to each other anatomically, but we did not," says Richtsmeier. "We found that the stronger statistical relationships existed between neural structures located near the top of the brain and boney features at the base of the skull."
To look at the correlations between the skull and the brain, the researchers first had to find locations that could be accurately found again and again. Locating reliable markers was easier on the rigid skull than on the brain. Co-author of the paper, Kristina Aldridge, former postdoctoral researcher at Penn State and now at Washington University, looked at the reproducibility of standard anatomical features on the skull and brain.
"We found that the brain landmarks people often use were highly variable and had the biggest errors in reproducibility," says Richtsmeier. "We eventually chose brain locations that were easier to identify reliably such as the most posterior point or the centroid of small neural structures."