Sexual Dimorphism in Volum of Human Cerebral Cortex of Different Lobes in Normal and Neurodegenerative Subjects - A Stereological and Macroscopical Study

Purpose: This study is designed to determine the sex differences in volume of human cerebral cortex in different lobes of left hemisphere 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 males, 34 females), 11 brains suffered from Alzheimer (4 males, 7=females), and 13 brains suffered from Parkinson (9 males, 4 females). The age range of males and females 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 the cortex in different lobes of left hemisphere is performed on photographs of 5mm serial coronal sections of this hemisphere by a point grid and using the Cavalieris principle. The results were analysed by t-student and non-parametrical Mann-Whitney statistical tests. Results: The volume of frontal cortex was significantly larger in males than females (p=0.005).Higher volumes of occipital and temporal cortices in males were also signigicant (p< 0.05).There was no significant difference between males and females in the volume of parietal cortex, although this cortex had more volume. in males (p=0.17). The sexual difference in volume of different lobes cortex was not significant in the subjects which were suffered from Alzheimer disease. There was no significant difference between two sexes regarding the volume of different lobes in the Parkinson subjects These subjects there was only a tendency. Conclusion: It is concluded that the volume of different lobes cortex of left hemisphere, except the parietal cortex, is significantly larger in males than females. Although the functional importance of these differences is not clear, scientists must be aware of them in morphological studies on brain pathologies. On the other hand, neurodegenerative diseases decrease the normal gender differences in volume of different lobes cortex, which can be due to more degeneration in males than females.