Correlation Between Gyral Window and Corpus Callosum: An MRI Study

Background:  In a previous study conducted by our lab comparing 14 male autistic individuals and 28 matched controls, the size of the gyral window directly correlated to the size of the corpus callosum. In our present study, we sought to increase our confidence in using gyral window and corpus callosum measurements as a biomarker in autism by validating our earlier findings using a new series of control subjects and identifying a normative range of measure. We investigated the measurements of and the relationship between the gyral window and corpus callosum in over 400 subjects ranging from ages 4.8 to 22.3, from the NIH Pediatric MRI data repository for normative developmental studies, the largest non-bias, multi-center, demographically balanced longitudinal study to date.

Objectives:  This study seeks to identify normative measurements of and the relationship between the gyral window and corpus callosum in control subjects in relation to age and gender during normal brain development.

Methods:  Using Release 4.0 of the NIH Pediatric MRI Data Repository for normative developmental studies, we identified the normalized gyral window depth by segmenting all gyral white matter by lobe using the parameters established by the NIH. A Euclidean distance map (EDM) of gyral white matter was constructed using MatLab. Measurement of gyral shape was identified by calculating the d tilde of each segment. The size of the d tilde correlates to the amount of gyrification in which the smaller the d tilde, the greater the gyrification; likewise, the larger the d tide, the lesser the gyrification. Following the same methods in our previous study, the displacement of the corpus callosum was then calculated and the relationship between gyral window and interhemispheric communication was analyzed separately using linear regression of gyral window with respect to corpus callosum displacement.

Results:  Gyral window measurements indicated that gyrification increased with age in both males and females in the frontal, temporal and parietal lobes and decreased with age in both males and females in the occipital lobe. There was no significant age difference between male and female groups overall, but there was significant dependence of gyral window upon age, lobe, hemisphere, age*sex, age*lobe, and age*hemisphere. There was evidence of a concomitant relationship between changes in gyral window measurements and corpus callosum.

Conclusions:  Results of this study provide a normative range for gyral window and corpus callosum measurements that can be used to distinguish variations in growth patterns that will allow us to accurately diagnose neurodevelopmental disorders such as autism through non-invasive MRI.