A number of studies in patients with Parkinson’s disease have reported increased iron concentrations in brain structures, notably the substantia nigra (SN), which may be prognostic of disease severity. One method for assessing iron deposition is to determine the relaxation rate (R2*, the sum of R2 and R2’) on MRI, in which inhomogeneities in the magnetic field due to iron deposition result in a more rapid signal decay and an increase in the relaxation rates.
R2* values in the SN, putamen and caudate nucleus were obtained in 70 PD patients at different disease stages; the sample included untreated de novo patients, treated early-stage patients and advanced-stage patients with L-dopa-related motor complications (Hopes et al. EAN 2015; abstract P1149). R2* values were found to be significantly higher in the SN, putamen and caudate nucleus of de novo patients compared to controls, suggesting iron overload at disease onset. R2* values in the SN were higher still in early-stage patients. Significant atrophy of the putamen and caudate nucleus was found in advanced-stage PD patients.
Similar results were seen in a longitudinal study that used R2* imaging (Ulla et al. PLoS One 2013;8:e57904; free full text at www.ncbi.nlm.nih.gov/pmc/articles/PMC3585727/pdf/pone.0057904.pdf). Over a three-year period, R2* increased in the SN and putamen in PD patients but not in controls. Variation in R2* was significantly correlated with worsening motor symptoms.
Reviewer: Dr. Susan Fox