Dementia in Parkinson disease: a proton magnetic resonance spectroscopy study.

BACKGROUND Magnetic resonance spectroscopy has been shown to be useful in differentiating idiopathic Parkinson disease (PD) from atypical parkinsonian syndromes such as progressive supranuclear palsy, multiple system atrophy, and corticobasal degeneration. OBJECTIVE To systematically investigate the utility of proton magnetic resonance spectroscopy in distinguishing between idiopathic PD with dementia (PDD) and without dementia. DESIGN Group comparisons and correlations of brain metabolites with clinical and neuropsychological variables. PATIENTS AND METHODS Metabolite concentrations were acquired from voxels localized to the basal ganglia and occipital cortex in 14 patients diagnosed as having idiopathic PDD, 12 patients with PD without dementia, and 13 matched control subjects. The 3 groups underwent clinical and neuropsychological assessment. RESULTS In the occipital region, N-acetylaspartate levels were significantly reduced in the PDD group relative to the PD and control groups. N-acetylaspartate values correlated with neuropsychological performance but not with severity of motor impairment. CONCLUSIONS N-acetylaspartate reduction in occipital lobes may be a marker for dementia in PD. The distribution of metabolite reduction differs from that reported in Alzheimer disease. These findings suggest that proton spectroscopy may serve as a metabolic marker of cognitive disturbance in patients with PD.