Abstract
PurposeTo study changes of iron content in basal ganglia in Parkinson’s disease (PD) through a three-year longitudinal follow-up of the effective transverse relaxation rate R2*, a validated MRI marker of brain iron content which can be rapidly measured under clinical conditions.MethodsTwenty-seven PD patients and 26 controls were investigated by a first MRI (t0). Longitudinal analysis was conducted among the 18 controls and 14 PD patients who underwent a second MRI (t1) 3 years after. The imaging protocol consisted in 6 gradient echo images obtained at different echo-times for mapping R2*. Quantitative exploration of basal ganglia was performed by measuring the variation of R2* [R2*(t1) – R2*(t0)] in several regions of interest.ResultsDuring the three-year evolution of PD, R2* increased in Substantia nigra (SN) (by 10.2% in pars compacta, p = 0.001, and 8.1% in pars reticulata, p = 0.013) and in the caudal putamen (11.4%, p = 0.011), without significant change in controls. Furthermore, we showed a positive correlation between the variation of R2* and the worsening of motor symptoms of PD (p = 0.028).ConclusionSignificant variation of R2* was longitudinally observed in the SN and caudal putamen of patients with PD evolving over a three-year period, emphasizing its interest as a biomarker of disease progression. Our results suggest that R2* MRI follow-up could be an interesting tool for individual assessment of neurodegeneration due to PD, and also be useful for testing the efficiency of disease-modifying treatments.
Highlights
Increased iron concentration was found in specific brain structures of patients suffering from Parkinson’s disease (PD)
Post mortem histological analysis [1], in vivo magnetic resonance imaging (MRI) [2,3,4,5,6,7] and transcranial sonography [8] studies are in agreement, highlighting iron deposition in the substantia nigra (SN) of PD patients, results are controversial for other basal ganglia (BG) structures such as the putamen [9,10,11]
Whereas no association was shown between iron deposition and disease duration, clinical scores correlated with SN iron load in PD patients [4,5,12], suggesting that the amount of SN iron could be a biomarker of disease severity
Summary
Increased iron concentration was found in specific brain structures of patients suffering from Parkinson’s disease (PD). Post mortem histological analysis [1], in vivo magnetic resonance imaging (MRI) [2,3,4,5,6,7] and transcranial sonography [8] studies are in agreement, highlighting iron deposition in the substantia nigra (SN) of PD patients, results are controversial for other basal ganglia (BG) structures such as the putamen [9,10,11]. To further investigate the link between brain iron changes and PD progression, a longitudinal approach involving both PD patients and normal subjects appears to be the most appropriate study design for distinguishing between the concomitant effects of normal aging and disease evolution over time. The amount of iron increases in the caudate nucleus, putamen [13,14,15,16] and cerebral cortex [17] during normal aging
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