Age-related metabolite changes and volume loss in the hippocampus by magnetic resonance spectroscopy and imaging

Magnetic resonance imaging (MRI) studies have produced controversial result s concerning the correlation of hippocampal volume loss with increasing age . The goals in this study were: 1) to test whether levels of N-acetyl aspar tate (NAA, a neuron marker) change in the hippocampus during normal aging a nd 2) to determine the relationship between hippocampal NAA and volume chan ges. Proton magnetic resonance spectroscopic imaging (H-1 MRSI) and MRI wer e used to measure hippocampal metabolites and volumes in 24 healthy adults from 36 to 85 years of age. NAA/Cho decreased by 24% (r = 0.53, p = 0.01) a nd NAA/Cr by 26% (r = 0.61, p < 0.005) over the age range studied, whereas Cho/Cr remained stable, implying diminished NAA levels. Hippocampal volume shrank by 20% (r = 0.64, p < 0.05). In summary, aging effects must be consi dered in H-1 MRSI brain studies. Furthermore, because NAA is considered a m arker of neurons, these results provide stronger support for neuron loss in the aging hippocampus than volume measurements by MRI alone. (C) 1999 Else vier Science Inc. All rights reserved.