[en] To determine, using proton magnetic resonance spectroscopy (¹H MRS) whether thalamotomy in patients with Parkinson's disease gives rise to significant changes in regional brain metabolism. Fifteen patients each underwent stereotactic thalamotomy for the control of medically refractory parkinsonian tremor. Single-voxel ¹H MRS was performed on a 1.5T unit using a STEAM sequence (TR/TM/TE, 2000/14/20 msec), and spectra were obtained from substantia nigra, thalamus and putamen areas, with volumes of interest of 7-8ml, before and after thalamotomy. NAA/Cho, NAA/Cr and Cho/Cr metabolite ratios were calculated from relative peak area measurements, and any changes were recorded and assessed. In the substantia nigra and thalamus, NAA/Cho ratios were generally low. In the substantia nigra of 80% of patients (12/15) who showed clinical improvement, decreased NAA/Cho ratios were observed in selected voxels after thalamic surgery (p<0.05). In the thalamus of 67% of such patients (10/15), significant decreases were also noted (p<0.05). Our results suggest that the NAA/Cho ratio may be a valuable criterion for the evaluation of Parkinson's disease patients who show clinical improvement following surgery. By highlighting variations in this ratio, ¹H MRS may help lead to a better understanding of the pathophysiologic processes occurring in those with Parkinson's disease