Decreased hippocampal N-acetylaspartate in the absence of atrophy in posttraumatic stress disorder

Background: Previous magnetic resonance imaging studies of posttraumatic stress disorder reported hippocampal volume loss. The goals of this study were 1) to determine the relationship between hippocampal atrophy and posttraumatic stress disorder in the absence of alcohol abuse, and 2) to test if loss of N-acetylaspartate (a neuron marker) in the hippocampus of posttraumatic stress disorder occurs separate from atrophy. In addition, volume changes in the entorhinal cortex were also explored. Methods: Eighteen male patients with combat-related posttraumatic stress disorder (mean age 51.2 ± 2.5 years) and 19 male control subjects (mean age 51.8 ± 3.2 years) were studied using magnetic resonance imaging and Proton magnetic resonance spectroscopic imaging. Both groups had no alcohol and drug abuse during the past 5 years. Results: Posttraumatic stress disorder and control subjects had similar volumes of hippocampus and entorhinal cortex. In contrast to volume, N-acetylaspartate was significantly reduced by about 23% bilaterally in the hippocampus of posttraumatic stress disorder when compared with control subjects, and creatine-containing compounds were reduced by 26% in the right hippocampus of posttraumatic stress disorder. Conclusions: N-acetyl asparate and creatine reductions imply that there are hippocampal abnormalities in posttraumatic stress disorder. Furthermore, these metabolite changes seem to be better indicators of posttraumatic stress disorder pathology than volume losses.