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New MRI Technique Shows Brain Cell Loss in Parkinsonís

Using new imaging techniques, scientists have for the first time documented changes in brain structures in people living with Parkinson's disease (PD). The study of people with early stage PD was reported in the November 26, 2012, online edition of Archives of Neurology, suggesting that the new imaging technique could be a tool for monitoring PD.

The loss of cells in the brain’s substantia nigra has long been the hallmark sign of PD. According to a recent theory of PD progression, after cells are lost in the substantia nigra, they are then lost in other brain structures, such as the basal forebrain.  Both of these areas are very small, lie deep in the brain, and are difficult to assess using current imaging techniques. The changes in the brain have only been reliably viewed by studying the brain after a person’s death. 

Researchers at the Massachusetts Institute of Technology, led by David A. Zigler, Ph.D., found a way to measure the size of these inner brain structures using a powerful type of magnetic resonance imaging (MRI). They recruited 29 people with PD severity ranging from mild to moderate. Study volunteers were on average 65 years old, and 11 were women. The scientists made four MRI scans of each volunteer’s brain, each time using a slightly different setting on the MRI machine. For comparison, the researchers performed the same procedure on 27 adults without PD, of similar age and education level.

Results

  • The researchers found that people with early stage PD had lost cells in the brain area known as the substantia nigra.  In people with more advanced disease, scans showed that cells in the basal forebrain had also been lost.
  • Scans showed that the volume of the part of the brain called the substantia nigra was smaller in people with early stage PD than in people without the disease, meaning that cells had died in that brain region.
  • Substantia nigra volume was about the same in people with early stages of PD as in those whose PD was rated as moderate.
  • Basal forebrain volume was smaller in people with moderate stage of PD than in healthy people or those with early PD.
  • Basal forebrain volume was about the same in healthy people as in people with early PD.

What Does It Mean?

Until very recently, loss of cells in inner brain structures — the hallmark of PD — could only be reliably observed by studying the brain after death. The new research represents an important tool for seeing and measuring the size of these parts of the brain in people living with PD. 

Doctors often refer people with suspected PD for an MRI. Usually, the MRI helps to rule out other diagnoses (e.g., vascular parkinsonism) because traditional MRI is not able to detect the minor changes that happen in early PD. This study shows that the brain changes in PD can be observed with a more powerful MRI (3 Tesla MRI), providing hope for a biomarker—a test for diagnosing and tracking PD progression.  But first it must be evaluated on more people, people with a wider range of severity in PD symptoms and in longitudinal studies. It will be helpful to test whether Parkinson’s disease progression as observed in a clinical exam correlates with the brain changes seen on an MRI.  For now, this approach to MRI scanning is not widely available.

Reference: Ziegler, D. A., Wonderlick, J. S., Ashourian, P., Hansen, L. A., Young, J. C., Murphy, A. J., et al. (2012). Substantia Nigra Volume Loss Before Basal Forebrain Degeneration in Early Parkinson Disease. Archives of Neurology, 1–7. doi:10.1001/jamaneurol.2013.597

Source Date: Dec 10 2012