The high complexity of cortical convolutions in humans remains a mystery for both engineers to measure and compare it, and for biologists to understand it. We developed a method for the quantification of the cortical area allowed by the process of folding. Our method uses accurate three-dimensional cortical reconstruction and compute local measurements of gyrification at thousands of points over the whole cortical surface. The potential of our method to identify and localize subregional gyrification abnormalities is illustrated by a clinical study on a group of children affected by 22q11 Deletion Syndrome compared to control individuals.