Hypoxic encephalopathy after near-drowning studied by quantitative 1H-magnetic resonance spectroscopy.

Early prediction of outcome after global hypoxia of the brain requires accurate determination of the nature and extent of neurological injury and is cardinal for patient management. Cerebral metabolites of gray and white matter were determined sequentially after near-drowning using quantitative 1H nuclear magnetic resonance spectroscopy (MRS) in 16 children. Significant metabolite abnormalities were demonstrated in all patients compared with their age-matched normal controls. Severity of brain damage was quantified from metabolite concentrations and ratios. Loss of N-acetylaspartate, a putative neuronal marker, from gray matter preceded that observed in white matter and was more severe. Total creatine decreased, while lactate and glutamine/glutamate concentrations increased. Changes progressed with time after injury. A spectroscopic prognosis index distinguished between good outcome (n = 5) and poor outcome (n = 11) with one false negative (bad outcome after borderline MRS result) and no false positive results (100% specificity). The distinction was made with 90% sensitivity early (after 48 h) and became 100% later (by days 3 and 4). This compared with 50-75% specificity and 70-100% sensitivity based upon single clinical criteria. MRS performed sequentially in occipital gray matter provides useful objective information which can significantly enhance the ability to establish prognosis after near-drowning.

Probable Alzheimer disease: diagnosis with proton MR spectroscopy.

PURPOSE: To distinguish probable Alzheimer disease (AD) from other dementias (ODs) and normality in the elderly. MATERIALS AND METHODS: A double-blind trial of proton magnetic resonance (MR) spectroscopy was performed, principally in gray matter, in the occipital cortex of 114 patients with dementia (AD [n = 65], OD [n = 39], or frontal lobe dementia [FLD] [n = 10]), 98 patients without dementia, and 32 healthy control subjects. RESULTS: Reduced levels of N-acetylaspartate (NAA) (P < .0005) and increased levels of myo-inositol (MI) (P < .0005) characterize AD. Patients with OD had significantly reduced levels of NAA (P < .01) but normal levels of MI (P [vs AD] < .0005). When MI/NAA was used, AD was distinguished from normality with 83% sensitivity and 98% specificity. When MI/creatine was used, OD was distinguished from AD and FLD with a negative predictive rate of 80%, sensitivity of 82%, and specificity of 64%. CONCLUSION: Hydrogen-1 MR spectroscopy enables identification of mild to moderate AD with a specificity and sensitivity that suggest clinical utility.

Abnormal cerebral metabolite concentrations in patients with probable Alzheimer disease.

To establish whether recently described abnormalities of peak ratios are the result of changes in metabolite concentrations, quantitative 1H magnetic resonance spectroscopy was performed in 10 patients with Alzheimer disease (AD) and seven normal elderly. CSF volumes, metabolite T1 and T2 relaxation rates, ratios and concentrations of N-acetyl residues, creatine, choline residues, myo-inositol, glutamine plus glutamate (Glx), and glucose were obtained. Difference spectroscopy and quantitative assays showed a 50% increase in myo-inositol (6.4-9.8 mM; P < 0.005) and a decrease in N-acetyl in occipital gray matter. A reduction in beta, gamma-Glx and a significant increase in intracerebral [glucose], greater than attributable to CSF, were defined. Choline concentration increased with age, but was not elevated above normal in AD patients. These findings indicate the need for quantitative 1H MRS to substantiate metabolite ratios. The increased myo-inositol concentration in AD is demonstrated by these studies.