CHANGES IN PUTAMEN N-ACETYLASPARTATE AND CHOLINE RATIOS IN UNTREATED AND LEVODOPA-TREATED PARKINSONS-DISEASE - A PROTON MAGNETIC-RESONANCE SPECTROSCOPY STUDY

We have carried out single-voxel proton magnetic resonance spectroscop y centered on the putamen both ipsilateral and contralateral to the wo rst affected side in nine subjects with drug naive idiopathic Parkinso n's disease (IPD); seven chronically levodopa-treated dyskinetic IPD s ubjects; and 11 age-matched healthy controls. Measurements of N-acetyl aspartate (NAA)/choline (Cho), NAA/(Creatine + Phosphocreatine) (Cr+PC r), and Cho/(Cr+PCr) were made. We found a significant reduction in NA A/Cho ratios from the putamen contralateral to the most affected side in the drug-naive group (p = 0.009), but not the levodopa-treated IPD groups compared with controls, There were no significant differences i n NAA/(Cr+PCr) or Cho/(Cr+PCr) ratios. In untreated IPD, reduced putam inal NAA/Cho ratios may reflect loss of nigrostriatal dopamine termina ls or alternatively indicate a functional abnormality of striatal puta minal neurons, such as membrane dysfunction due to striatal deafferent ation. This study suggests that NAA/Cho ratios may be affected by L-do pa therapy and this may provide a reversible marker of neuronal dysfun ction in the striatum.