Morphometry of corpus callosum: an anatomical study

There is a number of studies in literature concerning the diameters, morphology, size, age and sex-related differences of corpus callosum (CC) [1-8]. This scientific interest is due in the performance of callosotomies for intractable epilepsy and in the clinical features and experimental evaluations and observations related to the shape and size of CC. CC is the main fiber tract connecting the two cerebral hemispheres [9]. There is a topographic organization of callosal fibers, which represents the cortical regions to be connected [10]. Topographically, fibers connecting frontal regions travel through the front of CC and those connecting occipital cortices travel through the posterior part of CC. The role of CC in brain function is still a matter of debate. Agenesis of CC is a congenital abnormality with unclear etiology and pathogenesis, which results in various clinical pictures [11]. In contrast, total corpus callosotomy represents the therapy of choice for patients with intractable epilepsy. In this study we have measured the longitudinal diameters of human CC itself and its parts, the vertical and longitudinal diameters of brain hemispheres and the distances of CC to the frontal and occipital poles, in order to define the topographic location of CC in brain hemispheres and the way these anatomical structures interact to each other. Material and Methods The longitudinal diameters of CC in relation to vertical and longitudinal diameters of brain hemispheres were studied in 42 (23 males and 19 females, aged 30-40 years) formalin fixed adult brains. The brains were removed during autopsies were lack of any visible pathological findings. The technique used was as follows: immediately after removal of the brains from the cranial vault, they were fixed with basilar suspension in 10% formalin solution for four weeks. Thereafter the brains were dissected and CCs were prepared in all their lengths and the midsagittal line of each CC were identified. By using this line as an anatomical landmark, we cut the brains carefully in the midsagittal plane passing from the body of CC, the hemispheric fissure, the septum, third ventricle cavity and aqueduct (Fig. 1). Then methylene blue dye was administered over the medial cut surface of brain and CC; then the outlines of medial hemispheric surface and CC were copied on a transparent sheet of paper. On these papers, the longitudinal diameters of CC, splenium and genu were measured, as well as the distances between the frontal and the occipital poles and also between the superior and the inferior surfaces of brain hemispheres (Fig. 2). For study purposes, CCs were divided with the method proposed by Witelson [11], in which CC has been arbitrarily divided into three regions according to maximal straight length: the anterior third (genu), which contains fibers connecting prefrontal cortices; the mid-third (mid-body) of the CC, which Morphometry of corpus callosum: an anatomical study