Abstract #0607

Reversible NAA Decreases in Active MS Lesions Are Not Due Solely to Water Content Changes

Irene Vavasour¹, Cornelia Laule^1,2, Madeleine Hodgson³, David Li¹, Anthony Traboulsee⁴, Burkhard Maedler⁵, Alexander MacKay^1,3

¹Radiology, University of British Columbia, Vancouver, British Columbia, Canada; ²Pathology & Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada; ³Physics & Astronomy, University of British Columbia, Vancouver, British Columbia, Canada; ⁴Medicine (Neurology), University of British Columbia, Vancouver, British Columbia, Canada; ⁵Neurosurgery, University of Bonn, Germany

Previous magnetic resonance spectroscopy studies have shown a decrease in N-acetyl-aspartate (NAA) concentration when a new MS lesion appears followed by a subsequent rise. The most plausible explanation is that dilution from increased water content (WC) related to edema causes NAA to decrease while edema resolution leads to an NAA increase. Scanning monthly over 6 months, NAA concentrations of twelve new lesions were extracted using LCModel and corrected for relaxation and WC. Even after taking into account WC changes, NAA showed a reversible decrease in new lesions. The reversible NAA changes in new lesions are not a simple dilution effect.