RBD Patients: Early Identification of High-Risk Parkinson's Group with MRI

Samsung Medical Center Research Team Utilizes Neuromelanin-Sensitive MRI
Reducing the Burden of Unnecessary Comprehensive Testing

A new diagnostic strategy has been introduced that enables the early identification of high-risk patients with REM sleep behavior disorder (RBD)—those likely to convert to Parkinson's disease—using MRI (magnetic resonance imaging), which does not involve radiation exposure. Instead of conducting expensive, comprehensive tests on all patients, the approach involves first screening with MRI and then performing additional examinations only for those who need them.

On August 10, Samsung Medical Center announced that the research team led by Professor Joo Eunyeon from the Department of Neurology, Professors Kim Eungyeop and Son Beomseok from the Department of Radiology, and Professor Kim Jaerim from Sejong Chungnam National University Hospital has confirmed the potential of using neuromelanin-sensitive MRI (NM-MRI) to identify high-risk patients for Parkinson's disease.

REM sleep behavior disorder is a condition in which patients physically act out their dreams while sleeping, often shouting or flailing their arms and legs. It frequently appears as a prodromal stage prior to the onset of Parkinson's disease. However, not all patients progress to Parkinson's disease, making early identification of high-risk groups a clinically important challenge.

Currently, the representative test for assessing Parkinson's disease risk is the dopamine transporter (DaT) PET (positron emission tomography) scan. However, the high cost, limited availability at medical institutions, and the need for radioactive isotopes mean it is not feasible to apply this test to all RBD patients.

To address these issues, the research team focused on neuromelanin, a pigment found in dopamine neurons. Because neuromelanin decreases when dopamine neurons are damaged, analyzing signal intensity and volume with MRI allows for indirect assessment of the extent of dopamine neuron injury.

The researchers administered neuromelanin-sensitive MRI scans to 66 RBD patients and 30 healthy controls. Based on the results of dopamine PET scans, patients were divided into an abnormal group (37 individuals) and a normal group (29 individuals) for comparative analysis. The findings revealed that patients who showed abnormal findings on the dopamine PET scan also had significantly reduced volume and signal intensity of neuromelanin on MRI, whereas those with normal PET results showed no significant differences compared to healthy controls.

The research team stated that these results demonstrate neuromelanin-sensitive MRI can serve as an imaging biomarker reflecting dopamine neuron damage. However, they emphasized that MRI is not intended to replace existing PET scans, but rather to propose a new diagnostic strategy: first identifying high-risk groups with MRI and then administering PET scans only to patients who require further evaluation.

If adopted in clinical practice, this method could help reduce unnecessary comprehensive testing and allow medical resources to be focused on high-risk patients, while also lessening the testing burden on patients.

Professor Son Beomseok said, "Neuromelanin-sensitive MRI has the advantage of enabling repeated scans without radiation exposure and can be performed along with standard brain MRI scans." Professor Joo Eunyeon added, "Not all patients with REM sleep behavior disorder progress to Parkinson's disease. We expect these findings will help establish a tailored management system that adjusts examination and follow-up strategies based on each patient's risk for disease progression."

The findings were published in the latest issue of the international journal Brain Imaging & Behavior.

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