Age-related Brain Metabolic Changes up to Seventh Decade in Healthy Humans : Whole-brain Magnetic Resonance Spectroscopic Imaging Study.

PURPOSE: To study brain metabolic changes under normal aging and to collect reference data for the study of neurodegenerative diseases. METHODS: A total of 55 healthy subjects aged 20-70 years (n ≥ 5 per age decade for each gender) underwent whole-brain magnetic resonance spectroscopic imaging at 3T after completing a DemTect test and the Beck depressions inventory II to exclude cognitive impairment and mental disorder. Regional concentrations of N-acetylaspartate (NAA), choline-containing compounds (Cho), total creatine (tCr), glutamine and glutamate (Glx), and myo-inositol (mI) were determined in 12 brain regions of interest (ROIs). The two-sided t­test was used to estimate gender differences and linear regression analysis was carried out to estimate age dependence of brain regional metabolite contents. RESULTS: Brain regional metabolite concentrations changed with age in the majority of selected brain regions. The NAA decreased in 8 ROIs with a rate varying from -4.9% to -1.9% per decade, reflecting a general reduction of brain neuronal function or volume and density in older age; Cho increased in 4 ROIs with a rate varying from 4.3% to 6.1%; tCr and mI increased in one ROI (4.2% and 8.2% per decade, respectively), whereas Glx decreased in one ROI (-5.1% per decade), indicating an inhomogeneous increase of cell membrane turnover (Cho) with altered energy metabolism (tCr) and glutamatergic neuronal activity (Glx) as well as function of glia cell (mI) in normal aging brain. CONCLUSION: Healthy aging up to the seventh decade of life is associated with regional dependent alterations of brain metabolism. These results provide a reference database for future studies of patients.

Physiological neuronal decline in healthy aging human brain - An in vivo study with MRI and short echo-time whole-brain (1)H MR spectroscopic imaging.

Knowledge of physiological aging in healthy human brain is increasingly important for neuroscientific research and clinical diagnosis. To investigate neuronal decline in normal aging brain eighty-one healthy subjects aged between 20 and 70years were studied with MRI and whole-brain (1)H MR spectroscopic imaging. Concentrations of brain metabolites N-acetyl-aspartate (NAA), choline (Cho), total creatine (tCr), myo-inositol (mI), and glutamine+glutamate (Glx) in ratios to internal water, and the fractional volumes of brain tissue were estimated simultaneously in eight cerebral lobes and in cerebellum. Results demonstrated that an age-related decrease in gray matter volume was the largest contribution to changes in brain volume. Both lobar NAA and the fractional volume of gray matter (FVGM) decreased with age in all cerebral lobes, indicating that the decreased NAA was predominantly associated with decreased gray matter volume and neuronal density or metabolic activity. In cerebral white matter Cho, tCr, and mI increased with age in association with increased fractional volume, showing altered cellular membrane turn-over, energy metabolism, and glial activity in human aging white matter. In cerebellum tCr increased while brain tissue volume decreased with age, showing difference to cerebral aging. The observed age-related metabolic and microstructural variations suggest that physiological neuronal decline in aging human brain is associated with a reduction of gray matter volume and neuronal density, in combination with cellular aging in white matter indicated by microstructural alterations and altered energy metabolism in the cerebellum.

Whole Brain ¹H-Spectroscopy: A Developing Technique for Advanced Analysis of Cerebral Metabolism.

OBJECTIVE: Accompanying the advance of neuroscientific research and modern therapeutic methods, efforts have been made to develop more practical and effective advanced magnetic resonance (MR) spectroscopic techniques. METHODS: We present a brief overview on (1)H-MRS techniques in neuroradiological diagnosis and several application examples of recently reported whole brain MR spectroscopic imaging technique (wbMRSI). RESULTS: Despite the benefits of using established (1)H-MRS techniques both single voxel MR spectroscopy (SVS) and chemical shift imaging (CSI) techniques suffer from limited spatial coverage. It is always necessary to define prior to the MRS examination which brain structure is physiologically or pathologically involved and thus should be targeted with (1)H-MRS. In contrast, the advanced wbMRSI allows estimating metabolite changes within a much larger brain region and at multiple brain structures simultaneously. CONCLUSIONS: As a developing technique for advanced analysis of cerebral metabolism a wide application of the wbMRSI in both clinical diagnostics and neuroscience could be expected.