Boiagina O. D., Kostilenko Ju. P., Mangov A. V., Inyutochkina I. A.

MORPHOLOGY

Scentific article

Numerous studies of the corpus callosum conducted with traditional morphometric methods revealed a number of differences in the shape and size of the corpus callosum. However, there is no certainty as for their relation to age, gender and brain size. We set out as a goal to develop a simple method of corpus callosum metric analysis, which will enable further study of adults corpus callosum in order to identify individual diversity of its sexual dimorphism. Two samples from a series of head MRI tomograms of mentally healthy men and women (20 variants in each group) aged 32-56, performed in sagittal plane on T1, T2 wi, were used as data for study. Visual metric analysis was performed using the software RadiAnt Dicom Viewer. The proposed method is based on a geometric morphometric analysis of the shape of interhemispheric side profile of the corpus callosum, which is bordered by two arched circles closely fit to each other (in the area of rostrum and splenium). Each of the arched circles is a conjunction of the curves with different radius of the circle. We put its entire contour profile within the scalene rectangle, the long side of which is equal to its longitudinal dimension, and the short one is equal to the maximum height of the upper trunk prominence. The former we regard as the distance between the most protruding anterior point of the corpus callosum genu and the most protruding backward point of corpus callosum splenium and we call it the length of the corpus callosum along the subtense, meaning that this size does not coincide its actual length, because in its trunk corpus callosum forms an obtuse angle, opened downwards. The top of its corner curve corresponds to the most elevated point of its convexity and enables identifying of two thighs in the corpus callosum – the front one and back one. Their length can be determined by two lines connecting this corner point with forward-protruding genu point and back-protruding splenium point. Their total length will relate to the subtense as the sum of two legs to hypotenuse, and will be approximately equal to the actual length of the corpus callosum. Thus, in this study we achieved more objective assessment of individual variability of sexual dimorphism of the corpus callosum median profile on the basis of MRI scans due to the innovative changes we introduced in its morphometry technique. Those changes are based on the correct geometric approach to the analysis of planimetric figures with complex configuration. The resulting metric parameters in graphical format, being correlated with the values of the longitudinal dimension of the cranium, indicate that: a) while there is a direct relationship between the lengths of the corpus callosum along subtense and braincase, there is no corresponding correlation of its actual length, and the ratio coefficient between them (both of men and women) is absolutely the same (it is equal to 2.3, which is 0.3 less than along the subtense). Therefore, these measurements in adults can be rightfully assumed as constant values that express regularity in the proportional relationship between the corpus callosum and the size of the brain, as its volume is in direct proportion to that of the cranium; b) individual variability of both actual length, and separately, of two thighs of the corpus callosum is more pronounced in men, suggesting that the corpus callosum size of women is more stable; c) the average actual length of the corpus callosum in males is approximately 6 mm more than that of women; d) sexual dimorphism of the corpus callosum is also expressed in some non-equivalence between the length of its front and rear thighs. The latter in men is on the average of about 4 mm longer than in women.

corpus callosum, individual variation, sexual dimorphism, MRI

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«Bulletin of problems biology and medicine» Issue 2 part 1 (128), 2016 year, 353-359 pages, index UDK 611.813.9:616-071.3-073.763.5-053.85-055.1/.3