The MRI study of hippocampal volume and shape in the youth and older

Abstract

Objective In the base of the landmarks of the hippocampus idenffied with neighborhood structures,to measure volumes and shape of normal older age group and youth group's hippocampus and hippocampal head,body,tail.Methods Thirty younger people(age 20-29 years,youth group) and thirty older people (above 60 years,older age group)were scanned by MR ,anatomic landmarks were found ,which were constancy and easy to be recognized for segmentation hippocampus.The hippocampal volumes,average areas and number of the hippocampal layer were measured,the interelass data of two groups,different gender and sides were compared with statistics methods of t test and the hippocampal model were made with the three-dimensional reconstruction. Results All landmarks of 60 subjects could be distinguished clearly,such as uncal recess,triangle of the lateral ventricle,uncal apex et al. The discrepancies of two groups' volumes of gender had not statistical significance.The youth groups' volumes of left hippocampus,head,body and tail were (1250±174) ,(653±115) ,(372±116) ,(2277±109) mm~3,and the right were (1255±147),(657±129),(386±105),(2298±213) mm~3.There was no statistical significance between left and right(t=0.08,0.10,0.33,0.35,P ＞0.05).The older age groups' volumes of left hippocampus,head,body and tail were (660±109),(472±92),(181 ～ 73),(1313±163) mm~3,and the right were (717±116),(474±95),(240±75),(1432±171) mm~3.Older hippocampal volumes were obviously bigger in right tail than in left(t=2.21 ,P＜0.05) ,and other parts had not statistical significance (t=1.39,0.06,1.95,P ＞0.05).There were manifest statistical significance between two groups' left volumes of hippocampus and each parts (t=15.78,6.71,7.70,20.83,P＜ 0.05),and also right (t=15.76,6.26,6.15,17.36,P＜0.05).The hippocampal volumes and its three parts were obviously smaller in older than youth,especially the hippocampal head.The left average areas of youth and older groups' were (75±24),(56±21) mm~2 and the right were (73±22),(58±19) mm~2.Both two groups had manifest statistical significance(t=3.33,2.81,P＜ 0.01).The number of layers of youth and older groups' were (11.1±3.2),(7.9±3.9) layers,and the right were (11.5±3.7),(8.2±3.1) layers.Both two groups had manifest statistical significance (t=3.48,3.75,P＜ 0.05).The number of layers and average areas of hippocampal head were less in older than in youth group,and the shape of hippocampus become short and narrow.Conclusion According to the rule with landmarks that we selected,standardization measurement of the hippocampus may become possible and can be provided the basis of diagnosis and searching pathogenesis related to disease. Key words: Hippocampus; Magnetic resonance imaging