Magnetic resonance imaging of cerebral central sulci: a study of monozygotic twins

The cerebral central sulci, seat of the sensorimotor cortex, vary anatomically in form, length and depth among individuals and present a left/right asymmetry. The purpose of this work was to measure central sulcus's lengths, at the surface and in-depth, in each hemisphere of monozygotic twins in order to evaluate the influence of environmental factors on the morphometry and asymmetry of this structure. A measurement technique on MR images of the brains using 3 D software was developed. Two operators applied this technique to measure central sulcus lengths at the surface of the brain and in-depth in each hemisphere. Besides the fact that the technique developed gave high Intraclass Correlation Coefficients (ICC) for the surface lengths (mean value 0.94), and slightly less high for the in-depth length (mean value 0.87), we found a weak (from 0.57 to 0.73 for raw data) but significant ICC between homologous sulci in pairs of twins. In addition, the ICC for asymmetry indices were not significant. Hence, if central sulcus morphometry is in part genetically influenced, these results show that nongenetic factors are nonetheless important in their development.