N-acetylaspartate (NAA) has been proposed as a marker of neuronal density. Therefore, regional measurement of NAA by magnetic resonance spectroscopic imaging (MRSI) may provide a sensitive method for detection of selective neuronal loss, in contrast to conventional imaging techniques such as magnetic resonance imaging (MRI). To test this hypothesis, we produced selective neuronal injury by kainate-induced status epilepticus. Three days later three-dimensional 1H-MRSI was obtained and compared with conventional T2-weighted MRI and histological findings in normal and kainatetreated rats. Reduction of NAA determined by MRSI in piriform cortex, amygdala, and hippocampus correlated well with neuronal injury determined from histology. Changes of NAA, without any MRI changes in hippocampus, indicated greater sensitivity of MRSI for detection of neuronal injury. These results are consistent with the hypothesis that reduction of NAA measured by MRSI may be a sensitive marker of neuronal injury in vivo in a variety of disease states.
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