Neuromelanin magnetic resonance imaging of nigral volume loss in patients with Parkinson's disease.

Parkinson's disease (PD) is characterized by progressive degeneration of melanin-containing neurons in the substantia nigra pars compacta (SNc). Pathological change has not been detected by neuroimaging techniques in patients with PD in vivo. We examined 80 patients with PD to determine whether degeneration of the SNc is detectable in vivo by MRI. The age-matched controls consisted of 54 patients who had suffered mild acute ischemic stroke. Axial T1-weighted MRI were obtained with a 3-Tesla MRI scanner. The border of the neuromelanin-sensitive region in the SNc was traced manually on these images, and the volume of this area was calculated. The mean volumes for the left and right SNc were significantly reduced in patients with PD compared to the controls. Volume loss became marked in parallel with disease severity and duration. Neuromelanin MRI may be considered as a biomarker of nigral degeneration in patients with PD.