Anteroposterior Hippocampal Metabolic Heterogeneity: Three-dimensional Multivoxel Proton¹H MR Spectroscopic Imaging—Initial Findings

Abstract

Purpose:To quantify proton magnetic resonance (MR) spectroscopy-detectable metabolite concentrations along anteroposterior axis of hippocampus in healthy young and elderly subjects. Materials and Methods:Young (three women, three men; age range, 25-35 years) and elderly (four women, two men; age range, 68 -72 years) groups underwent MR imaging and proton MR spectroscopic imaging at 3 T in this HIPAA-compliant prospective study and gave institutional review board-approved written consent. Volume of interest was centered on and tilted parallel to hippocampal anteroposterior plane. Absolute N-acetylaspartate (NAA), choline, and creatine levels were obtained in each voxel, with phantom replacement. Results:Mean NAA, creatine, and choline concentrations in the young group were higher in posterior hippocampus (12.9 mmol/L Ϯ 2.0 [standard deviation], 7.8 mmol/L Ϯ 1.2, 2.3 mmol/L Ϯ 0.4, respectively) than anterior hippocampus (8.0 mmol/L Ϯ 1.1, 6.0 mmol/L Ϯ 1.4, 1.5 mmol/L Ϯ 0.2; P ϭ .005, .02, and .0002, respectively). In the elderly group, mean concentrations were higher in posterior hippocampus (8.6 mmol/L Ϯ 0.9, 5.6 mmol/L Ϯ 0.6, 1.5 mmol/L Ϯ 0.2, respectively) than anterior hippocampus (7.2 mmol/L Ϯ 1.0, 2.4 mmol/L Ϯ 0.3, 1.0 mmol/L Ϯ 0.2; P ϭ .006, .0001, .04, respectively). Mean concentrations were significantly higher in the young group (13.2 mmol/ L Ϯ 1.0, 7.4 mmol/L Ϯ 0.8, 2.1 mmol/L Ϯ 0.3, respectively) than in the elderly group (9.0 mmol/L Ϯ 1.0, 5.8 mmol/L Ϯ 0.8, 1.8 mmol/L Ϯ 0.3; P ϭ .0001, .01, .05, respectively). Posteroanterior metabolic gradients differed: NAA decreased faster in the young group (Ϫ1.0 mmol/L ⅐ cm Ϫ1 ) than the elderly group (Ϫ0.7 mmol/ L ⅐ cm Ϫ1 ); creatine and choline concentrations decreased faster in the elderly group (Ϫ0.8 and Ϫ0.058 mmol/ L ⅐ cm Ϫ1 , respectively) than the young group (Ϫ0.16 and Ϫ0.008 mmol/L ⅐ cm Ϫ1 , respectively). No left-right metabolic differences were found. Conclusion:Significant metabolic heterogeneity was observed between groups and along anteroposterior axis of healthy hippocampus in both groups. Age matching and consistent voxel placement are important for correct comparisons of both absolute metabolic levels and metabolite ratios in longitudinal intra-and intersubject cross-sectional studies. Note: This copy is for your personal, non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, use the Radiology Reprints form at the end of this article.T he hippocampus, a part of the limbic system located on the floor of the temporal horn of the lateral ventricle (1), is crucial for memory consolidation, spatial cognition, perception of temporal ordering of events (2), mood regulation (3), and negative feedback inhibition of glucocorticoids (4). It is functionally connected to a wide range of cortical and subcortical brain regions, including the cingulate gyrus, orbitofrontal and temporal cortices, amygdala, olfactory cortex, and thalamic nuclei (5). Given this complex function and connectivity, it is not surpr...

Metabolic Abnormalities in the Hippocampus of Patients with Schizophrenia: A 3D Multivoxel MR Spectroscopic Imaging Study at 3T

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Neurofunctional topography of the human hippocampus

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Delineation of hippocampal subregions using T1-weighted magnetic resonance images at 3 Tesla

“…Recent reviews suggest that the hippocampus can be divided along its long axis (Fanselow & Dong, 2010) consistent with evidence from proton MR spectroscopy (King et al, 2008) and functional MR (Demaster & Ghetti, 2013) imaging studies. Posterior and anterior hippocampal regions have a unique pattern of connectivity and have been linked to different functions (Poppenk, Evensmoen, Moscovitch, & Nadel, 2013; Nadel, Hoscheidt, & Ryan, 2013) that may be of relevance to neuropsychiatric disorders such as schizophrenia (Szeszko et al, 2002).…”