Efecto regional, de la edad y el sexo en la espectroscopia por resonancia magnética cerebral

Organization of neurochemical interactions in young and older brains as revealed with a network approach: Evidence from proton magnetic resonance spectroscopy (1H-MRS)

Aging is associated with alterations in the brain including structural and metabolic changes. Previous research has focused on neurometabolite level differences associated to age in a variety of brain regions, but the relationship among metabolites across the brain has been much less studied. Investigating these relationships can reveal underlying neurometabolic processes, their interdependency, and their progress throughout the lifespan. Using ¹H-MRS, we investigated the relationship among metabolite concentrations of N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myo-Inositol (mIns) and glutamate-glutamine complex (Glx) in seven voxel locations, i.e., bilateral sensorimotor cortex, bilateral striatum, pre-supplementary motor area, right inferior frontal gyrus and occipital cortex. These measurements were performed on 59 human participants divided in two age groups: young adults (YA: 23.2 ± 4.3; 18-34 years) and older adults (OA: 67.5 ± 3.9; 61-74 years). Our results showed age-related differences in NAA, Cho, and mIns across brain regions, suggesting the presence of neurodegeneration and altered gliosis. Moreover, associative patterns among NAA, Cho and Cr were observed across the selected brain regions, which differed between young and older adults. Whereas most of metabolite concentrations were inhomogeneous across different brain regions, Cho levels were shown to be strongly related across brain regions in both age groups. Finally, we found metabolic associations between homologous brain regions (SM1 and striatum) in the OA group, with NAA showing a significant correlation between bilateral sensorimotor cortices (SM1) and mIns levels being correlated between the bilateral striata. We posit that a network perspective provides important insights regarding the potential interactions among neurochemicals underlying metabolic processes at a local and global level and their relationship with aging.

From fetus to older age: A review of brain metabolic changes across the lifespan

INTRODUCTION

The knowledge of metabolic changes across the lifespan is poorly understood. Thus we systematically reviewed the available literature to determine the changes in brain biochemical composition from fetus to older age and tried to explain them in the context of neural, cognitive, and behavioural changes.

METHODS

The search identified 1262 articles regarding proton magnetic resonance spectroscopy (1H MRS) examinations through December 2017. The following data was extracted: age range of the subjects, number of subjects studied, brain regions studied, MRS sequence used, echo time, MR system, method of statistical analysis, metabolites analyzed, significant differences in metabolites concentrations with age as well as the way of presentation of the results.

RESULTS

82 studies that described brain metabolite changes with age were identified. Reports on metabolic changes related to healthy aging were analyzed and discussed among six basic age groups: fetuses, infants, children, adolescents, adults, and the elderly as well as between groups and during the whole lifetime.

DISCUSSION

The results presented in the reviewed papers provide evidence that normal aging is associated with a number of metabolic changes characteristic for every period of life. Therefore, it can be concluded that the age matching is essential for comparative studies of disease states using 1H MRS.

Sex differences in brain metabolite concentrations in healthy children - proton magnetic resonance spectroscopy study (1HMRS)

Purpose

The aim of this ¹HMRS study was to define sex-related differences in metabolic spectrum between healthy children. Forty-nine girls and boys aged 6-15 years were examined.

Material and methods

Volume of interest was located in seven brain regions: frontal lobes, basal ganglia, hippocampi, and cerebellum.

Results

Statistical analysis of the results showed significantly higher (p < 0.05) myo-inositol concentrations relative to the total concentrations in the boys than the girls, as well as higher absolute N-acetyl aspartate concentrations in the left frontal lobes in girls. No other significant differences were shown, except for trends in differences.

Conclusions

In clinical practice the diagnostic process first of all focuses on assessing concentrations of metabolites to relative cerebellum concentration. Thus, the findings of the present study allow the conclusion that when analysing the results of ¹HMRS studies in children it is not necessary to take into account the child's gender.

Regional Differences in the Concentrations of Metabolites in the Brain of Healthy Children: A Proton Magnetic Resonance Spectroscopy (1HMRS) Study

Background

The aim of this ¹HMRS study was to identify any potential regional differences in the metabolic spectrum in the brains of healthy children.

Material/Methods

Forty-nine healthy children aged 6–15 years (mean 11.6 years) were examined, including 21 girls and 28 boys. A 1.5T MR system (xi Signa HD 1.5T General Electric) was used in patient examinations. The VOI (Volume of Interest) was defined in 7 locations: the frontal lobe in the right and left hemispheres, the basal ganglia in the right and left hemispheres, hippocampus in the right and left hemispheres and cerebellum. SAGE 7.0 software was used for the analysis of data obtained from the ¹HMRS study. Differences in the concentrations of metabolites in various regions of the brain in children were verified using the t-test for independent samples.

Results

There were significant differences in concentration levels between various brain regions for all the examined metabolites. NAA was the metabolite characterized by the greatest regional variation with significant differences being observed between all locations. Only in the case of Lip/Cr and the ratio of the Lip concentration to the sum of the concentrations of all the metabolites no significant differences could be observed.

Concluisons

The results of the study show that a child’s brain is inhomogeneous. The results underline the need of the regional differences in the concentrations of metabolites being taken into account when comparing the results of ¹HMRS studies in children.