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

Abstract

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.

Attention, learning, and memory in posttraumatic stress disorder

“…Magnetic Resonance Imaging (MRI) and 1H Magnetic Resonance Spectroscopic Imaging (MRSI) acquisition and processing were described in detail elsewhere (Schuff et al, 2001). In brief, the participants were scanned on a 1.5-T VISIONTM Magnetic Resonance (MR) system using a double spin echo sequence (DSE) with Time Repetition (TR)/Time Echo (TE) 1/TE 2 = 2500/20/80-ms timing, 3-mm slice resolution, and a volumetric magnetization-prepared rapid gradient echo sequence with TR/TE/Time of Inversion (TI) = 10/4/300-ms timing, 15°-flip angle, 10 × 1.0 mm 2 inplane resolution, and 1.4-mm thick coronal partitions for structural MRI.…”

“…Crowell, Kieffer, Siders, & Vanderploeg, 2002). Decreased performance on neurocognitive tasks may be of particular relevance to PTSD because multiple studies have documented decreases in hippocampal volume (Bremner et al, 1997;Bremner, Randall, Scott, Bronen, et al, 1995;Gilbertson et al, 2002;Gurvits et al, 1996;Stein, Koverola, Hanna, Torchia, & McClarty, 1997;Villarreal et al, 2002) and decreased reduced concentrations of the neuronal marker N-acetyl aspartate (NAA; Freeman, Cardwell, Karson, & Komoroski, 1998;Schuff et al, 2001). Hippocampal atrophy in PTSD was associated with decreased function in explicit memory in a sample of combat veterans (Bremner, Randall, Scott, Bronen, et al, 1995), though not in women with history of childhood sexual assault (Stein et al, 1997).…”

“…We reported that NAA is reduced in the hippocampus of PTSD patients in the absence of hippocampal volume loss (Schuff et al, 2001). NAA occurs at high concentrations in neurons and is virtually nondetectable in other tissues (Birken & Oldendorf, 1989).…”

“…This study compares attention, learning, and memory performance in the sample of Vietnam combat veterans with and without posttraumatic stress disorder reported in the Schuff et al (2001) study. Given our finding of reduced hippocampal NAA in PTSD, our original hypothesis was that PTSD participants, even after controlling for comorbid alcoholism, substance abuse, and depression, would perform worse on tests of attention and declarative memory when contrasted with normal comparison participants.…”

MR-based in vivo hippocampal volumetrics: 1. Review of methodologies currently employed

“…[28][29][30][31] Similarly, several groups found smaller bilateral hippocampi in patients with PTSD, 32,33 whereas others were unable to find significantly smaller hippocampi in PTSD. [34][35][36] In MD, significantly smaller bilateral hippocampal volumes have been reported by some, 11,37,38 but not by others. 39,40 Part of the discrepancy among research findings may be attributed to the use of different methods for establishing hippocampal volume.…”