Sexual Dimorphism in Surface Anatomical Parameters of Parahippocampal Cortex in Normal Subjects and Those Suffering From Alzheimer and Parkinson's Diseases - a Stereologic and Macroscopic Study

Purpose: This study was designed to determine sex differences in the surface anatomical parameters (surface area and thickness) of the left parahippocampal cortex in healthy right - handed subjects and right - handed subjects suffering from Alzheimer and Parkinson's diseases. Materials and Methods: This cross-sectional descriptive study was performed on 72 normal human brains (38 males, 34 females); 11 brains were afflicted with Alzheimer's (4 males, 7 females) and 13 brains were stricken with Parkinson's (9 males, 4 females). The age of the males and females in each group was similar.The right and left hemispheres of each brain were used for neuropathological diagnoses and stereological analyses, respectively. Unbiased stereological methods (with point and linear grids) were employed, and photographs of 5mm serial coronal sections of the left hemispheres helped estimate the left parahippocampal cortex thickness and surface areas. The results were analyzed with t-student and non- parametrical Mann-Whitney statistical tests. Results: The outer surface areas of the left parahippocampal cortex in the right - handed healthy males and females were 18.8±6.3 and 16.6±5.1cm2, respectively. The inner surface areas of the left parahippocampal cortex in the right - handed healthy males and females were 14.7±6.1 and 14.3±5.1cm2, respectively. The mean surface areas of the left parahippocampal cortex in the right-handed healthy males and females were 16.8±6 and 15.5±5cm2, respectively. There were no significant differences in the outer, inner and mean surface areas of the left parahippocampal cortex between two sexes in the healthy right - handed subjects. The thickness of the left parahippocampal cortex in the right-handed healthy males and females was 3.1±0.9 and 2.7±0.7 mm, respectively. Therefore, the thickness of this cortex in the females was 12.9% the size of that in the males (p=0.03). The surface anatomical parameters (surface areas and thickness) of the left parahippocampal cortex were similar between two sexes in the patients suffering from Alzheimer's disease. The outer and mean surface areas of the left parahippocampal cortex in Parkinson's disease sufferers were similar between two sexes, but the inner surface area of this cortex in the Parkinsonian females was significantly smaller than that in the Parkinsonian males (p=0.05). The thickness of the left parahippocampal cortex in the Parkinsonian males had a tendency (0.05<p<0.1) to be smaller than that in the Parkinsonian females. Conclusion: The left parahippocampal cortex in right - handed healthy males is thicker than that in right-handed females. The normal sexual difference in the left parahippocampal cortex thickness disappears in Alzheimer's disease. Although the left parahippocampal cortex in Parkinsonian females has a tendency to be thicker than that in Parkinsonian males, this difference is not significant. The changes of normal sexual dimorphism in the thickness of the left parahippocampal cortex in these two neurodegenerative diseases can be due to a more severe degeneration of this cortex in males.