Metabolic and cognitive response to human traumatic brain injury: a quantitative proton magnetic resonance study

Proton magnetic resonance spectroscopy (1H-MRS) offers a unique insight into brain cellular metabolism following traumatic brain injury (TBI). The aim of the present study was to assess change in neurometabolite markers of brain injury during the recovery period following TBI. We studied 19 TBI patients at 1.5, 3, and 6 months postinjury and 28 controls. We used 1H-MRS to quantify N-acetylaspartate (NAA), creatine (Cre), choline (Cho), and myoinositol (mIns) in occipitoparietal gray matter (GM) and white matter (WM) remote from the primary injury focus. Neuropsychological testing quantified cognitive impairment and recovery. At 1.5 months, we found cognitive impairment (mean z score = -1.36 vs. 0.18,p < 0.01), lower NAA (GM: 12.42 mM vs. 13.03, p = 0.01; WM: 11.75 vs. 12.81, p < 0.01), and elevated Cho (GM: 1.51 vs. 1.25, p < 0.01; WM: 1.98 vs. 1.79, p < 0.01) in TBI patients compared with controls. GM NAA at 1.5 months predicted cognitive function at outcome (6 months postinjury; r = 0.63, p = 0.04). GM NAA continued to fall by 0.46 mM between 1.5 and 3 months (p = 0.02) indicating continuing neuronal loss, metabolic dysfunction, or both. Between 3 and 6 months, WM NAA increased by 0.55 mM (p = 0.06) suggesting metabolic recovery. Patients with poorer outcomes had elevated mean GM Cho at 3 months postinjury, suggesting active inflammation, as compared to patients with better outcomes (p = 0.002). 1H-MRS offers a noninvasive approach to assessing neuronal injury and inflammation following TBI, and may provide unique data for patient management and assessment of therapeutic efficacy.

Biochemical markers of cognition: a proton MR spectroscopy study of normal human brain

In the current study we explored the relationship between neurometabolites measured by proton magnetic resonance spectroscopy (1H-MRS) and cognitive ability assessed with a battery of neuropsychological tests. Forty-five participants were recruited from the local college community, and examined utilizing neuropsychological testing and 1H-MRS. Our central finding was that N-acetylaspartate (NAA) was associated with overall neuropsychological performance (F(1,42) = 23.16, p < 0.0001], r2 = 0.35. We found an even stronger association between timed neuropsychological measures and NAA (F(1,42) = 31.15, p < 0.0001], r = 0.43. These results reveal the specific relationship of NAA to neuropsychological functioning in normal human brain. The current observations in healthy individuals are consistent with the hypothesis that variability in NAA levels and neuropsychological performance may be related to mitochondrial function.

Biochemical markers of intelligence: a proton MR spectroscopy study of normal human brain

Proton magnetic resonance spectroscopy (1H-MRS) offers a unique non-invasive approach to measurement of N-acetylaspartate (NAA) and choline (Cho), putative markers of neuronal and glial integrity. Previous studies revealed that these neurochemicals predict cognitive impairment in diseased subjects, although little is known about their relationship to cognitive functioning in healthy people. We measured the concentrations of NAA and Cho in the left occipitoparietal white matter of 26 healthy adults and compared them with intellectual performance assessed by the Wechsler Adult Intelligence Scale-3. We found that NAA (b = 0.6, p < 0.01) and Cho (b = -0.42, p < 0.01) were independently associated with the Full-Scale Intelligence Quotient. Together, these metabolites accounted for a large proportion of the variance in intelligence (r2 = 0.45). Possible mechanisms underlying these correlations, such as mitochondrial function and myelin turnover, are discussed. 1H-MRS is a sensitive new tool to assess the neuronal underpinnings of cognitive function non-invasively.