Localised proton MR spectroscopy of brain metabolism changes in vegetative patients

Abstract

We examined 14 vegetative brain-injured patients with proton magnetic resonance single-volume spectroscopy (1H MRS) at 1.5 T to establish whether there were changes in relative concentrations of N-acetyl aspartate (NAA), choline (Cho) and creatine (CR) metabolites from those found in healthy brains. Spectra were obtained from two different (2 x 2 x 2 cm) volumes of interest in the left and in the right frontal cortex, normal on MRI. All spectra revealed abnormalities compared with normal spectra obtained from age-matched control subjects. Values outside the normal range for at least one of the metabolite ratios were observed in all patients. Cho/Cr was markedly higher and NAA/Cho and NAA/Cr were markedly lower than in the control subjects. At different times six patients regained awareness and the ability to obey commands, and four were re-examined; changes in metabolite ratios were observed, which were different in individual patients. The NAA/Cho ratio reaches statistical significance in discriminating between the patients with a poor outcome (death or prolonged vegetative state) and those who regained awareness; the dividing line appears to be at a value of about 1.6.

Disorders of consciousness after acquired brain injury: the state of the science

“…A recent ASL-MRI study in patients in MCS showed a profound decrease in blood flow in anterior cortical midline structures. 101 Finally, MRI spectroscopy, a measure of biochemical changes in the brain, has uncovered severe metabolic cortical 102 and thalamic 103 neuronal dysfunction in DOC, with probable prognostic value. …”

Evaluation of Delayed Neuronal and Axonal Damage Secondary to Moderate and Severe Traumatic Brain Injury Using Quantitative MR Imaging Techniques

“…Thus, NAA is considered a neuronal and axonal marker, and its concentration decreases in brain lesions that cause neuronal or axonal loss. Decreased NAA after TBI was already demonstrated in the WM, [30][31][32][33][34] CC, 13,35 gray matter, [30][31][32]36 thalamus, 37 and hippocampus and basal ganglia, 38 in both subacute 28,30,33 and late phases. [31][32][33][34][35]38 Our results showed a significantly decreased NAA/Cr ratio mean value in the CC of the posttraumatic patient group, re- flecting axonal loss in this location due to TBI.…”

Neuroimaging and Outcome Assessment in Vegetative and Minimally Conscious State

“…Previous studies using single-voxel technique have shown in brain-injured subjects a significant correlation between unfavorable outcome and reduction of marker NAA in occipitoparietal white and gray matter (WM and GM) (Brooks et al, 2000;Friedman et al, 1999;Ross et al, 1998;Yoon et al, 2005), frontal WM (Garnett et al, 2000), parietal WM (Shutter et al, 2004), brainstem (Carpentier et al, 2006), splenium of the corpus callosum (Sinson et al, 2001;Cecil et al, 1998), and thalamus (Uzan et al, 2003), increase in choline a marker for cell membrane disruption in frontal WM (Garnett et al, 2000) and occipitoparietal WM and GM (Brooks et al, 2000;Cecil et al, 1998;Ross et al, 1998;Yoon et al, 2005), and increase in Glx in occipital GM and parietal WM (Shutter et al, 2004). In particular, NAA levels seem to discriminate patients who recovered from coma from those who died or remained in persistent VS (Ricci et al, 1997). Uzan et al (2003) carried out a thalamic proton MRS in patients in VS resulting from severe TBI.…”