| BackgroundThe hippocampus is located at the bottom of the temporal horn of the lateral ventricle.Human learning,cognition and memory are closely related to limbic system.Hippocampus is one of the important components of limbic system.A large number of studies have shown that hippocampus is closely related to neuropsychiatric diseases such as schizophrenia,depression and Alzheimer’s disease.These diseases develop slowly and lack sensitive judgment methods in the early stage.Therefore,hippocampal morphological measurement becomes an evaluation hippocampus is the main mode of normal state or pathological state.Because of its small size and complex structure,MRI has good soft tissue contrast,which is the most commonly way to observe the morphology of hippocampus.With the development of magnetic resonance imaging technology,higher field strength and higher resolution images can more clearly reflect the morphology and internal fine structure of the hippocampus.Therefore,in recent years,some scholars have found that there are some small abnormal signals in the hippocampus,which are mainly located between the dentate gyrus,the subcategory and the hippocampal horn,which are called hippocampal sulcal cavities(HSCs).HSCs showed circular or curvilinear shape on oblique coronal view and crescent shape on axial view.The signal characteristics of HSCs were the same as those of CSF on T1WI and T2WI.Some scholars speculated the origin of HSCs from the perspective of embryonic development.During the embryonic development of hippocampus,the hippocampal fissure was not completely closed,and the congenital cystic remnant was formed at the lateral edge of hippocampal fissure.Therefore,it is inferred that HSCs may be a developmental variation.Some scholars have found that there are arteriovenous vessels in the hippocampal fissure,and they think that HSCs may be the enlarged Virchow Robin space.Some scholars also adhere to the "circulation destruction theory",and they think that HSCs may be microvascular lesions related to hypoxic-ischemic diseases.There are also different opinions on the clinical significance of HSCs.Previous studies have found that HSCs are related to cognitive function,while some recent studies have shown that HSCs are not correlated with cognitive function.There is no consensus on whether HSCs are related to hippocampal volume and age.At present,most of the researches on hippocampal volume are carried out in patients with hippocampal diseases.Due to the differences in research level,sample size,calculation tools and standardized methods,the results are different.The research objects of HSCs are mostly the patients with cognitive function related diseases.The age range is narrow and the middle-aged and elderly people live in groups.The research on the normal population,especially the young group,is relatively less.At the same time,there is a lack of unified and systematic research on the normal group.Therefore,the first part of this study aims to measure the hippocampal volume of normal people by manual sketching measurement method,and to evaluate the correlation between hippocampal volume and gender,lateral sex,age and intracranial volume.The second part is to evaluate the detection rate and number of HSCs in normal population and the correlation with gender,side,age and hippocampal volume.To provide reference data for the study of hippocampal function morphology and the screening and diagnosis of hippocampal diseases.Section one:Measurement and evaluation of hippocampal volume in healthy population by magnetic resonance imagingPurpose:We valuate the correlation between hippocampal volume and gender,lateral,age and intracranial volume in healthy population,so as to provide reference data for the study of hippocampal function morphology and the diagnosis of clinical related diseases.Materials and methods:A total of 187 subjects(81 males and 106 females,aged 6-88 years,with an average age of 48.15±19.5years).The subjects were divided into six age groups:group 1:28 cases under 25 years old;group 2:24 cases aged 26-40 years old;group 3:41 cases aged 41-40 years;group 4:41 cases aged 51-60 years;group 5:29 cases aged 61-70 years old;group 6:24 cases over 70 years old.All the subjects underwent conventional sequence scanning(T1WI,T2WI,FLAIR,DWI)and coronal Ti sequence,axial T2 sequence of hippocampus.The images were transmitted to the post-processing workstation.The boundary of hippocampus was delineated by mouse,and the area of corresponding layer was calculated.Then the volume of this layer was obtained by multiplying the layer thickness.The absolute hippocampal volume was obtained by the accumulation of all layers.The hippocampal volume was corrected by division and covariance.t test was used to compare absolute and relative hippocampal volumes between left and right sides and different genders.ANOVA was used to compare absolute and relative hippocampal volumes among six age groups.Pearson correlation test was used to analyze the correlation between age and intracranial volume.Results:187 cases were included in this study.The absolute volume of the right hippocampus was 2297.42±301.31 mm3,and the absolute volume of the left hippocampus was 2270.42±302.40 mm3.The right side was larger than the left side,and the difference was statistically significant(P=0.000).After correction by division and covariance,the relative volume of the right side was still larger than that of the left side,and the difference was statistically significant(P=0.000,0.000).The absolute volume of male hippocampus was 4665.78±643.56 mm3 and that of female was 4492.67 ± 551.303 mm3.The absolute volume of male hippocampus was larger than that of female(P=0.049).After correction by division and covariance,the relative volume of female hippocampus was larger than that of male(P=0.006,0.000).Among the six age groups,except for the first age group,the absolute hippocampal volumes of the left and right sides decreased slightly with the increase of age.There were significant differences in the absolute hippocampal volumes between the left and right sides of each age group by analysis of variance(right F=2.568,P=0.028;left F=2.701,P=0.022).In addition to the first age group,the relative hippocampal volumes of the left and right sides also decreased slightly with the increase of age.After analysis of variance,there were significant differences in the relative hippocampal volumes between the left and right sides of each age group(Divide Right side F=3.927,P=0.002;Left side F=4.005,P=0.002;Covariance Right side of F=3.380,P=0.006;Left side F=3.382,P=0.006).Pearson correlation analysis showed that absolute hippocampal volume and relative hippocampal volume had no correlation with age(P=0.985,r=0.001;Division,relative volume and age P=0.568,r=0.042;Covariance,relative volume and age P=0.516,r=0.038).There was no correlation between absolute hippocampal volume,relative hippocampal volume and intracranial volume(P=0.579,r=-0.04;P=0.283,r=-0.079;P=0.929,r=0.007).Conclusions:The volume of right hippocampus was larger than that of left hippocampus in healthy population.The absolute hippocampal volume of male was larger than that of female,but the corrected relative hippocampal volume of female was larger than that of male.The volume of hippocampus was the largest in 25-40 years old,decreased slightly with age after 40 years old.Pearson correlation analysis showed that there was no correlation between hippocampal volume and age,no correlation between hippocampal volume and intracranial volume.Section two:Hippocampal Sulcal Cavities in normal population by magnetic resonance imagingPurpose:We analyzed the detection rate and number of HSCs in healthy population,and the correlation between HSCs and gender,lateral,hippocampal volume and age,so as to provide reference data for the study of hippocampal function morphology.Materials and Methods:A total 187 healthy subjects were scanned with 3.0 MRI(TiWI,T2WI,FLAIR and DWI),coronal T1 sequence,axial T2 sequence of hippocampus.The intracranial volume and the left and right hippocampal volumes were measured respectively.The hippocampal volume was corrected by division method.The detection rate of HSCs and the number of HSCs on the left and right sides were counted.Chi square test was used to compare the detection rate of HSCs in different genders,and t-test was used to compare the number of HSCs in different genders and sides.According to the number of HSCs,they were divided into four groups:0,1-5,6-10,and more than 10.The absolute hippocampal volume,corrected relative hippocampal volume and mean age between groups were compared by ANOVA.Finally,Pearson correlation test was used to analyze the correlation between the number of HSCs and the absolute hippocampal volume,corrected relative hippocampal volume and age.Results:In 187 cases,the detection rate of HSCs was 95%,and there was no significant gender difference in the detection rate of HSCs(P=0.448).There was no significant difference in the number of HSCs between left and right sides(P=0.093).The number of HSCs detected in women was more than that in men.There was no significant difference in absolute hippocampal volume and relative hippocampal volume between groups(P=0.943,0.287).There was significant difference in average age between groups(P=0.000).The results of least significant difference(LSD)showed that there were significant differences between the first group and the third group and the fourth group(P=0.013,0.000),the second group and the fourth group(P=0.000),the third group and the fourth group had statistical significance(P=0.005).The correlation coefficients between HSCs and absolute hippocampal volume,relative hippocampal volume and age were 0.316,-0.005 and 0.055,respectively.Conclusions:There was a high detection rate of HSCs in healthy population.There was no significant gender difference in the detection rate of HSCs.There was no significant difference in the number of HSCs between left and right sides.HSCs had a low correlation with age,but no correlation with hippocampal volume. |
PDF Full Text Request