Imaging advances in Parkinson’s disease

Imaging in Parkinson’s disease diagnosis has been used primarily to rule out conditions that might mimic Parkinson’s. The traditional thinking is that the Parkinson’s brain appears normal in MRI scans.

However, scientists at the University of British Columbia (UBC) MRI Research Centre in Vancouver are challenging this view. They are using MRI in a novel way to reveal changes in the Parkinson’s brain that are not detected in conventional scans. Research funded by

Parkinson Society Canada is pointing to the possibility of an imaging-based diagnostic tool for Parkinson’s disease, improved guidance for deep brain stimulation surgery, and new ways to measure the progression of Parkinson’s disease in the brain.

Dr. Alexander Rauscher, a physicist and research associate at the UBC MRI Research Centre, has developed and validated a new imaging technique that is extremely sensitive to iron, more accurate at assessing iron content, and yields better and sharper images of the brain and veins than can be obtained with conventional MRI scans. This new technique is called susceptibility weighted imaging (SWI) with multiple echoes.

Excessive iron in the brain has been linked to the death of dopamine-producing brain cells in Parkinson’s disease. With his multi echo SWI method, Rauscher has already found a good correlation between overall iron content in the substantia nigra, which is the area of the brain affected in Parkinson’s disease, and disease severity, as measured by the Unified Parkinson’s Disease Rating Scale (UPDRS).

“Using MRI to detect elevated iron content in the substantia nigra, or other brain regions, would provide a new measurement that could lead to earlier diagnosis of Parkinson’s,” says Rauscher. His novel MRI technique has potential for widespread use particularly in other neurological diseases where iron accumulation plays a role.

Rauscher’s research on susceptibility weighted imaging with multiple echoes, was published in the Journal of Magnetic Resonance Imaging in January 2010. The study was funded by Parkinson Society Canada.

As a direct result of this study, Rauscher and his colleagues have found that the high resolution and high contrast of SWI enables clear visualization of the subthalamic nucleus in MRI. “The subthalamic nucleus is a small structure in the brain and it is a target for deep brain stimulation which alleviates Parkinson’s disease symptoms in some people,” says Rauscher, “but it is difficult to identify in conventional MRI scans.” Reliable, direct targeting of the subthalamic nucleus with clear identification of shape and location could eliminate one step in DBS surgery and dramatically shorten the procedure which typically takes six to eight hours. A research paper on this was published in the Journal of Neuroradiology in 2009.

Rauscher presented his findings on iron and UPDRS rating at the joint annual meeting of the International Society for Magnetic Resonance in Medicine in Stockholm, Sweden, in May 2010.

In complementary research, Dr. Martin McKeown, a professor of medicine at the University of British Columbia and clinical director of the Pacific Parkinson’s Research Centre, is working with Rauscher to see if iron is deposited in specific patterns in Parkinson’s disease, making the technique even more sensitive.

McKeown and colleagues are also using conventional MRI (collected at the same time as the SWI) and novel analysis methods to look for changes in the shape of brain structures in people with Parkinson’s disease. They are then examining whether those shape changes correlate with specific Parkinson’s symptoms and disease severity.

“If we can tell, from the change in shape of a part of the brain, whether a person will have more severe tremor, be more rigid, have worsening memory and so on, this may allow us to predict how a person’s Parkinson’s disease will progress,” says McKeown. “One of the challenging things about Parkinson’s disease is that it varies tremendously from person to person. If we could target individuals who are at risk for specific symptoms, we could become more efficient and effective at offering them treatment.”