Abstract
Although NAA is often used as a marker of neural integrity and health in different neurologic disorders, the temporal behavior of WBNAA is not well characterized. Our goal therefore was to establish its normal variations in a cohort of healthy adults over typical clinical trial periods. Baseline amount of brain NAA, Q(NAA), was obtained with nonlocalizing proton MR spectroscopy from 9 subjects (7 women, 2 men; 31.2 ± 5.6 years old). Q(NAA) was converted into absolute millimole amount by using phantom-replacement. The WBNAA concentration was derived by dividing Q(NAA) with the brain parenchyma volume, V(B), segmented from MR imaging. Temporal variations were determined with 4 annual scans of each participant. The distribution of WBNAA levels was not different among time points with respect to the mean, 12.1 ± 1.5 mmol/L (P > .6), nor was its intrasubject change (coefficient of variation = 8.6%) significant between any 2 scans (P > .5). There was a small (0.2 mL) but significant (P = .05) annual V(B) decline. WBNAA is stable over a 3-year period in healthy adults. It qualifies therefore as a biomarker for global neuronal loss and dysfunction in diffuse neurologic disorders that may be well worth considering as a secondary outcome measure candidate for clinical trials.
Highlights
AND PURPOSE: NAA is often used as a marker of neural integrity and health in different neurologic disorders, the temporal behavior of WBNAA is not well characterized
WBNAA is stable over a 3-year period in healthy adults
It qualifies as a biomarker for global neuronal loss and dysfunction in diffuse neurologic disorders that may be well worth considering as a secondary outcome measure candidate for clinical trials
Summary
Baseline amount of brain NAA, QNAA, was obtained with nonlocalizing proton MR spectroscopy from 9 subjects (7 women, 2 men; 31.2 Ϯ 5.6 years old). The WBNAA concentration was derived by dividing QNAA with the brain parenchyma volume, VB, segmented from MR imaging. Human Subjects Nine healthy subjects (7 women, 2 men; 31.2 Ϯ 5.6 years old [range, 24 – 43 years]) were recruited for this study. Their “healthy” status was based on negative answers to a questionnaire listing 28 neurologic disorders before the examination and an MR imaging deemed “unremarkable” by a neuroradiologist afterward.
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