Search

Abstract: Magnetic Resonance Spectroscopy is based on the chemical shift property of the atom nuclei when a magnetic field is applied. This technique offers invaluable information about living tissues with [...]

Background: Mild cognitive impairment (MCI) of an amnestic type is a common condition in older people and highly predictive of Alzheimer's disease (AD). To date, there is no clear consensus regarding the best antecedent biomarker to predict early conversion to AD. Objective: The aim of the study is to demonstrate that 1H magnetic resonance spectroscopy (MRS) of the brain in MCI patients may predict early conversion to dementia within the 2-year period after baseline assessment. Methods: A cohort of patients fulfilling the criteria of amnestic MCI were enrolled consecutively. At baseline the patients underwent neuropsychological examination, standard blood tests and APOE genotype. ¹H-MRS (1.5 T) of the brain was carried out by exploring two areas: the posteromedial bilateral parietal lobe and left medial occipital lobe. The patients were followed up to detect conversion to probable AD according to the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association group criteria. Results: After a 2-year follow-up, 27 (38%) patients converted to AD. The mean N-acetyl-aspartate/creatine (NAA/Cr) ratio in the posteromedial bilateral parietal cortex was 1.38 in converters versus 1.49 in non- converters (p<0.0001). An NAA/Cr ratio equal to or lower than 1.43 in this area predicted conversion to probable AD at 74.1% sensitivity and 83.7% specificity (area under the curve: 0.84; 95% CI 0.73 to 0.92). The cross-validated accuracy of classification was 82%, which reaches 85% when the APOE4 genotype and memory test are included in the analysis. In the left medial occipital lobe, the predictive value was somewhat lower with 85.2% sensitivity and 61.4% specificity (area under the curve: 0.8; 95% CI 0.69 to 0.89). Neither the APOE4 genotype nor leuco-araiosis was predictive of conversion to dementia. Conclusion: MRS is a valuable biomarker to predict early conversion to dementia in patients with amnestic MCI. [ABSTRACT FROM AUTHOR]

Rationale and objectives: Autism and attention-deficit/hyperactivity disorder (ADHD) are neurodevelopmental disorders whose pathophysiology is mostly unknown. As far as the symptoms are different and, in some aspects, opposed, we hypothesize that there must be biochemical differences in the brain of the afflicted children. The aim of the study is to analyze comparatively the metabolite concentration of the cerebral white matter in autism, in ADHD, and in a control group of healthy children to test the hypothesis that N-acetyl aspartate (NAA) is decreased in autism and increased in ADHD. Patients and methods: We included 21 autistic children according to DSM-IV criteria, 8 children with ADHD meeting the respective criteria of DSM-IV, and 12 healthy controls of similar age. Single-voxel proton magnetic resonance spectroscopy was performed on all of them with an echo time of 30 milliseconds and a repetition time of 2500 milliseconds. The voxel was placed in the left centrum semiovale. Metabolite ratios relative to creatine were reported for NAA, choline, and myoinositol. Results: Although we did not observe differences between autistic children and controls, we found a mean higher concentration of NAA in the left centrum semiovale of ADHD children (2.2; SD, 0.21) than that found in autistic children (1.88; SD, 0.18) and controls (1.91; SD, 0.01), which was significant (P = .01 in parametric and in nonparametric test). Conclusion: We conclude that white matter of autistic children does not present alterations on MRS. We hypothesize that the higher concentration of NAA in the white matter of ADHD points to mitochondrial hypermetabolism. This may constitute a new substrate in the pathophysiology and merits further research. [Copyright &y& Elsevier]