Different Signals of Magnetic Resonance Imaging and Ultrasound from Substantia Nigra in Parkinson's Disease and Control - Is Iron the Cause?

Motor symptoms of Parkinson's disease are caused by a progressive degeneration of substantia nigra, a small structure located deep in the brain. The cause of this process is unknown but may be related to iron mediated oxidative stress. The aim of this study was to understand the mechanism of the change of magnetic resonance and ultrasound signals found in patients with Parkinson's disease, which were attributed by several authors to an important increase of the concentration of iron in substantia nigra. USG and MRI measurements were performed on phantoms simulating human brain to which high amounts of iron were introduced. The USG signal was unaffected by insertion of iron-loaded ferritin, while it was by insertion of glial tissue. Injections of iron-loaded ferritin and iron ions to the phantoms decreased T-2 relaxation time. Our results suggest that the observed change of the signal from Parkinsonian brains is probably due to a proliferation of glia and not to an increase of the concentration of iron.