Sexual Dimorphism in Human Brain Weight and Volume of Gray and White Matter in Normal and Neurodegenerative Subjects - A Stereological and Macroscopic Study

Purpose: This study is designed to determine the sex differences in brain weight and volume of left hemisphere and its gray and white matters in right-handed normal subjects and the right-handed subjects which were suffered from Alzheimer and Parkinson diseases. Materials and Methods: This study was performed on 72 normal human brains (38 male, 34 female), 11 brains suffered from Alzheimer (4 male, 7 female), and 13 brains suffered from Parkinson (9 male, 4 female). The age range between male and female in each group was similar. The brains were fixed in 4% formalin. The brainstem was removed and two hemispheres were separated by a midsagittal section. The right hemisphere was used for neuropathological diagnosis and the left one was used for morphometrical analysis. Volume estimation of left hemishere and its gray and white matters is performed on photographs of 5 mm serial coronal sections of this hemisphere by a point grid using the Cavalieri's principle. The results were analyzed by t- student, non parametrical Mann - Whitney, and Z (proportional) statistical tests. Results: In normal subjects, brain weight, volume of left hemisphere and volume of its gray and white matters were significantly smaller in female. The proportion of gray matter volume to left hemisphere volume did not have significant difference between two genders in normal subjects. None of parameters had significant sex difference in subjects which were suffered from Alzheimer disease. In subjects suffered from Parkinson disease, the brain weight and the volume of gray matter in left hemisphere were significantly smaller in female, but other parameters did not have any significant difference between two genders. Conclusion: It is concluded that brain weight and the volume of left hemisphere its gray and white matters are greater in male than female, although the functional importance of these differences is unclear. On the other hand, neurodegenerrative diseases decrease the normal gender differences in brain, which can be due to more degeneration in male than female.