Proton MR Spectroscopy for Monitoring Pathologic Changes in the Substantia Nigra and Globus Pallidus in Parkinson Disease

OBJECTIVE. This retrospective study aimed to examine the relationship between the ratio of N-acetyl aspartate (NAA) to creatine in the substantia nigra (SN) and globus pallidus (GP) and the Hoehn-Yahr stage and Unified Parkinson Disease Rating Scale (UPDRS) score determined for patients with Parkinson disease (PD). MATERIALS AND METHODS. Thirty patients with PD who underwent proton MR spectroscopy (1H-MRS) and for whom a Hoehn-Yahr stage and a UPDRS score for PD were determined were retrospectively reviewed. Hydrogen-1-MRS was used to measure the metabolite levels in the bilateral SN and GP. RESULTS. The mean (+/- SD) age of the patients was 67.7 (+/- 10.6) years. The mean UPDRS score was 40.5 +/- 13.9. Fourteen patients had PD of Hoehn-Yahr stages 1-2, and 16 patients had PD of Hoehn-Yahr stages 3-5. The NC ratio (the NAA-to-creatine ratio for the initially symptomatic side or the body divided by the NAA-to-creatine ratio for the contralateral side) for the bilateral GP (BGPNC) was significantly lower in the patients with stages 1-2 PD than in the patients with stages 3-5 PD (0.68 +/- 0.23 vs 0.84 +/- 0.11; p = 0.023). The NAA-to-creatine ratio for the initially symptomatic side of the SN was negatively correlated with the UPDRS score (r = -0.379; p = 0.039). CONCLUSION. In early PD, the changes in the GP are more pronounced on the side affected at the onset of PD, which may contribute to the development of asymmetric symptoms and signs. Hydrogen-1-MRS shows promise as a modality for evaluating PD.