The microstructure of white matter in male to female transsexuals before cross-sex hormonal treatment. A DTI study
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Fig. 1
Sagittal and axial maps of fractional anisotropy (FA) showing sex differences. FA is bilaterally lower in female than in male controls in the superior longitudinal fasciculus (SLF). Control females also show lower than control male FA values in the forceps minor (Fm) and the cingulum (C). The group skeleton used for the between group contrast study is green. The red color shows the clusters of significantly decreased FA in female compared to male controls. The threshold for significance was set at p < 0.05 corrected for multiple comparisons. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 2
Histograms showing the FA means between control females (black), male to female transsexuals (MtF) (red) and control males (green). MtF transsexuals significantly differed from female and male controls in almost of all the fascicles in which control males differed from control females. SLF: superior longitudinal fasciculus; IFOF: infero frontooccipital fasciculus. ∗At least p < 0.01. For SD see Table 4 . (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Abstract
Background
Diffusion tensor imaging (DTI) has been shown to be sensitive in detecting white matter differences between sexes. Before cross-sex hormone treatment female to male transsexuals (FtM) differ from females but not from males in several brain fibers. The purpose of this paper is to investigate whether white matter patterns in male to female (MtF) transsexuals before commencing cross-sex hormone treatment are also more similar to those of their biological sex or whether they are more similar to those of their gender identity.
Method
DTI was performed in 18 MtF transsexuals and 19 male and 19 female controls scanned with a 3 T Trio Tim Magneton. Fractional anisotropy (FA) was performed on white matter of the whole brain, which was spatially analyzed using Tract-Based Spatial Statistics.
Results
MtF transsexuals differed from both male and female controls bilaterally in the superior longitudinal fasciculus, the right anterior cingulum, the right forceps minor, and the right corticospinal tract.
Conclusions
Our results show that the white matter microstructure pattern in untreated MtF transsexuals falls halfway between the pattern of male and female controls. The nature of these differences suggests that some fasciculi do not complete the masculinization process in MtF transsexuals during brain development.
Keywords:
Diffusion tensor imaging, Transsexualism, Sex differences, Superior longitudinal fasciculus, Forceps minor, Cingulum, Corticospinal tractTo access this article, please choose from the options below
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