Proton MR spectroscopic changes in Parkinson's diseases after thalamotomy

To investigate whether there are significant changes in regional brain metabolism in patients with Parkinson's disease before and after thalamotomy using proton magnetic resonance spectroscopy (¹H MRS). Fifteen patients underwent 15 stereotactic thalamotomies for control of medically refractory parkinsonian tremor. Single-voxel ¹H MRS was carried out on a 1.5 T unit using stimulated-echo acquisition mode (STEAM) sequence (TR/TM/TE, 2000/14/20 ms). Spectra were obtained from substantia nigra, thalamus and putamen areas with volumes of interests (7-8 ml) in patients before and after the surgery. Metabolite ratios of NAA/Cho, NAA/Cr and Cho/Cr were calculated from relative peak area measurements. We evaluated alterations of metabolite ratios in brain metabolism in Parkinson's disease patients with clinical outcome following thalamotomy. NAA/Cho ratios showed generally low levels in substantia nigra and thalamus in Parkinson's disease patients with clinical improvement following thalamotomy. In 80% (12/15) patients, decreased NAA/Cho ratios were observed from the selected voxels in substantia nigra after thalamic surgery (P<0.05). The ratios were also significantly decreased in thalamus in 67% (10/15) patients with clinical improvement (P<0.05). Our results suggest that NAA/Cho ratio may be a valuable criterion for evaluation of Parkinson's disease patients with the clinical improvement following surgery. ¹H MRS may be a useful utility for the aid in better understanding the pathophysiologic process in Parkinson's disease patients on the basis of the variation of NAA/Cho ratio.