Neuronal laterality in Parkinson's disease with unilateral symptom by in vivo ¹H magnetic resonance spectroscopy

RATIONALE AND OBJECTIVES. The authors investigate whether there is a lateral effect of ¹H magnetic resonance spectroscopy (MRS) observable metabolite ratios between the symptomatic and the asymptomatic side in Parkinson's disease with unilateral symptoms. METHODS. Localized in vivo ¹H MRS was used to measure the metabolite levels in the symptomatic and the asymptomatic sides of the substantia nigra (SN) and putamen-globus pallidus (PG) in Parkinson's disease with unilateral symptom (n = 15). The metabolite ratios of N-acetylasparatate (NAA)/creatine (Cr), and choline-containing compounds (Cho)/Cr in the symptomatic side were compared with those in the asymptomatic side. According to the symptomatic duration, the authors evaluated whether there was a specific correlation between laterality and the clinical stage. RESULTS. Significant metabolic lateral effect of NAA/Cr ratio was established between the symptomatic and the asymptomatic sides of SN and PG in Parkinson's disease with unilateral symptoms (P = 0.03). The decreased NAA/Cr ratio was calculated in at least one of the selected regions in SN and PG, indicating neuronal loss. The main observations were that NAA/Cr ratios were reduced in the left symptomatic side (n = 7; P = 0.001) and reduced to a lesser degree in the right symptomatic side (n = 8; P = 0.03 [PG], P = 0.21 [SN]) and that there was no significant laterality of other metabolite ratios. CONCLUSIONS. On the basis of NAA/Cr ratios between the symptomatic and the asymptomatic sides, the present ¹H MRS study shows a significant neuronal laterality in Parkinson's disease with unilateral symptoms. In vivo ¹H MRS may provide a diagnostic marker for neuronal dysfunction in Parkinson's disease with unilateral symptoms.