DIFFERENTIATION OF MULTIPLE SYSTEM ATROPHY FROM IDIOPATHIC PARKINSONS-DISEASE USING PROTON MAGNETIC-RESONANCE SPECTROSCOPY

Proton magnetic resonance spectroscopy, localized to the lentiform nucleus, was carried out in 7 patients with the pure or predominantly striatonigral variant (SND) of multiple system atrophy (MSA), 5 patients with the olivopontocerebellar variant of MSA, 9 patients with a clinical diagnosis of idiopathic Parkinson's disease (IPD), and 9 healthy age-matched controls. The MSA group with predominantly striatonigral involvement showed a significant reduction in the N-acetylaspartate (NAA)/creatine ratio (median, 1.19; range, 0.96-2.0; P < 0.02) compared with the NAA/ creatine ratio from the control group (median, 1.76; range, 1.61-2.0). In contrast, the IPD group had a normal NAA/ creatine ratio (median, 1.82; range, 1.19-2.31; P > 0.5). The NAA/creatine ratio was markedly reduced in 6 of the SND patients and in only 1 IPD patient. The choline/creatine ratio was also significantly lower in the SND group (median, 1.02; range, 0.91-1.23; P < 0.04) compared with the control group (median, 1.22; range, 1.05-1.65). The IPD group showed a normal lentiform choline/creatine ratio (median, 1.13; range, 0.89-1.65; P = 0.25) compared with controls. The olivopontocerebellar group also showed a significant reduction in the NAA/creatine ratio from the lentiform nucleus (median, 1.47; range, 1.22-1.68; P < 0.01) compared with the controls sis well as a nonsignificant reduction in the choline/creatine ratio (median, 0.93; range, 0.85-1.27; P < 0.4). In vivo quantification of absolute metabolite concentrations was possible in 7 MSA patients and 6 controls and confirmed an absolute reduction of choline-containing compounds and NAA in the MSA group compared with controls with no significant difference in the creatine concentrations between the MSA group and the controls. The reduction of the NAA/creatine ratio from the lentiform nucleus in the MSA groups probably reflects neuronal loss, occurring predominantly in the putamen. Proton magnetic resonance spectroscopy is a useful, noninvasive technique to help differentiate MSA from IPD.