A group of Korean researchers has recently released a review thesis on Parkinson’s and Parkinsonian syndrome that compiled all the findings of related brain magnetic resonance images, drawing attention from the medical community.

In the substantia nigra of a healthy person (left) and Parkinson’s patients, the black shadows show the loss of dopamine.
In the substantia nigra of a healthy person (left) and Parkinson’s patients, the black shadows show the loss of dopamine.

The thesis, written by Professors Bae Yun-jung and Kim Jong-min of Seoul National University Bundang Hospital, is significant as a global review of imaging biomarkers for Parkinson's disease, the hospital said Tuesday.

Parkinson’s is a common neurodegenerative disorder caused by the loss of dopamine-producing cells in the midbrain's substantia nigra (SN). The symptoms include slow movements, muscle switches or stiffness, and postural instability.

Medical professionals make the diagnosis of Parkinson’s disease by observing the symptoms and conducting a neurologic examination. However, to distinguish it from Parkinsonian syndrome or secondary Parkinsonism, they need medical imaging tests like MRI.

The SNUBH’s review thesis compiled all recent findings on nigral imaging, one of the imaging biomarkers used for Parkinson’s diagnosis. The thesis includes imaging of the fiber trajectories and orientations of dopaminergic neurons in the brain. These are nigrosome imaging, neuromelanin imaging, quantitative iron mapping, and diffusion-tensor imaging.

The article also explains volumetry of the brain related to the symptoms of Parkinson’s and Parkinsonian syndrome.

For diagnosing Parkinson’s, imaging of the structural change of substantia nigra using various MRI techniques is important. In the past, it was difficult to observe the detailed structure of SN with previous MRI. However, the advent of 3-T and 7-T susceptibility-weighted imaging dense screening has made it possible to shoot them in greater detail. (T stands for Tesla, and the higher the following number, the higher the image's resolution.)

By visualizing nigrosome, the affected area of the brain, and identifying the areas of cell loss, precise diagnosis has become possible.

Another way of diagnosing Parkinson's disease is by observing the distribution of neuromelanin (NM). NM is a neuroprotective substance produced with the secretion of dopamine in the substantia nigra. Through dense observation of NM using MRI, the change in the amount of dopamine in the brain could be detected to diagnose Parkinson’s.

Neuromelanin accumulates in neurons. If the neurons are lost due to Parkinson’s disease, NMs disappear together. Therefore, by observing the amount of NMs, the amount of dopamine secretion could be found, which helps the diagnosis of the early stage of Parkinson’s and its prognosis during treatment.

In addition, using MRI to analyze the distribution of iron in the brain is also helpful for Parkinson’s diagnosis. The NMs distributed over substantia nigra have a characteristic of holding onto irons entering the brain. The problem occurs when the quantity of iron found in the substantia nigra surpasses the amount that NMs can hold onto. The iron accumulated on SN is known to create stress for the brain tissues and kills the cells. Hence, iron overload in SN can lead to Parkinson’s disease.

Through diffusion-tensor imaging (DTI), structural changes of the brain could be detected to make a diagnosis. For example, Parkinson’s patients tend to show more loss of SN volume.

Professors Kim Jong-min (left) of the Department of Neurology and Bae Yun-jung of the Department of Radiology at Seoul National University Bundang Hospital
Professors Kim Jong-min (left) of the Department of Neurology and Bae Yun-jung of the Department of Radiology at Seoul National University Bundang Hospital

“Simple MRI test has a high utility rate as a biomarker to detect underlying changes.” Professor Bae said. “With various imaging techniques, observing the structural change of the brain and the distribution and the number of neural substances in the brain can help diagnose the early stage of Parkinson’s. In addition, it could be helpful for prevention and plans for treatment.”

Professor Kim also said, “MRI imaging that was overlooked as a way of diagnosis, treatment, and long-term observation was found to be useful. Thus, its importance was highlighted once again. With the development of radiology, the diagnosis of Parkinson’s in its early stages has become possible. Hence, if you have symptoms of slow movement and shaking, do not consider it as a sign of aging butplease visit a nearby hospital.”

The article was published online in Radiology, a worldwide journal in the field.

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