Evidence for cortical dysfunction in clinically non-demented patients withParkinson's disease: a proton MR spectroscopy study

Objectives-To investigate whether proton magnetic resonance spectroscopy (H -1 MRS) can detect cortical dysfunction in non-demented patients with Parki nson's disease, and to correlate changes with cognitive function on formal neuropsychological testing. Methods-Multivoxel H-1 MRS was performed in 17 patients with levodopa treat ed idiopathic Parkinson's disease without clinical dementia, and 10 age mat ched control subjects. Measurements of N-acetylaspartate (NAA)/choline (Cho ), NAA/cresttine+phosphocreatine (Cr), and Cho/Cr were obtained from right and left temporoparietal cortex and occipital cortex. Fourteen patients wit h Parkinson's disease underwent a full battery of neuropsychological testin g including performance and verbal subtests of the WAIS-R, Boston naming te st, FAS test, and California verbal learning test. Results-There were significant temporoparietal cortex reductions in NAA/Cr ratios in right and left averaged spectra of the patients with Parkinson's disease (p=0.012 after Bonferroni correction) and in spectra contralateral to the worst clinically affected limbs of the patients with Parkinson's dis ease compared with controls (p = 0.003 after Bonferroni correction). There was a significant correlation between reduction in NAA/Cr ratios and measur es of global cognitive decline, occurring independently of motor impairment (p=0.019). Conclusions-This study suggests that H-1 MRS can detect temporoparietal cor tical dysfunction in non-demented patients with Parkinson's disease. Furthe r longitudinal studies are needed to investigate whether these H-1 MRS chan ges are predictive of future cognitive impairment in the subset of patients with Parkinson's disease who go on to develop dementia, or occur as part o f the normal Parkinson's disease process.