Acute and late changes in N-acetyl-aspartate following diffuse axonal injury in rats: an MRI spectroscopy and microdialysis study.
N-acetyl-aspartate (NAA) measured by proton nuclear magnetic resonance spectroscopy (1H-NMR) has been used as a marker of neuronal injury in many cerebral pathologies. Therefore, we evaluate the roles of microdialysis vs. 1H-NMR as techniques to assess NAA (NAAd; NAA/Creatine ratio) in the living brain, and compare the results with whole brain NAA (NAAw), analyzed by HPLC after diffuse traumatic brain injury (TBI). Acute (4 h post-injury survival) and late (48 h survival) changes were studied in a sham-operated group (Sham, n = 4), and two injured groups (TBI/4 h, n = 8; TBI/48 h, n = 7). Baseline NAAd was 8.17 +/- 1 microM, and there was no significant difference between groups. There was only a small (twice of control), but transient increase in NAAd in the TBI/4 h group after trauma. Baseline NAA/Cr ratio was 1.35 +/- 0.2, which did not change significantly between baseline, 1, 2, 3, 4 and 48 h or between groups after TBI. Whole brain NAAw (baseline 8.5 +/- 0.5 mmol kg-1 wet weight) did not differ significantly between groups before and after TBI. Diffuse TBI did not produce long-term changes in NAA, assessed by three different methods. These results may indicate that NAA is not a sensitive marker of the severity of diffuse axonal damage. However, further studies are needed to evaluate whether confounding factors such as microdialysis probe, voxel position and non-regional tissue homogenization might have influenced our data.
Alessandri
B
B
Division of Neurosurgery, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0631, USA.
al-Samsam
R
R
Corwin
F
F
Fatouros
P
P
Young
H F
HF
Bullock
R M
RM
D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D015415:Biomarkers; D001930:Brain Injuries / Q000175:diagnosis / Q000378:metabolism*; D020833:Diffuse Axonal Injury / Q000175:diagnosis / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D008297:Male; D017551:Microdialysis; D051381:Rats; D017207:Rats, Sprague-Dawley
D015415:Biomarkers; D001224:Aspartic Acid; C000179:N-acetylaspartate