What is GLIMPS?

GLIMPS is a multicenter (inter)national project: Glucose Imaging in Parkinsonian Syndromes. More than fifteen centers are currently participating in the project. The project has been initiated by prof. dr. K.L. Leenders in 2012 and is coordinated by the department of Neurology, University Medical Center Groningen, The Netherlands. GLIMPS has originally been developed to create a national database containing FDG PET scans of patients with different neurodegenerative brain diseases together with clinical data of these patients. The data is stored anonymously and used to ease clinical diagnosis for each participating patient, but also to enable research projects. In the meantime the project has also resulted in international involvement.

What are neurodegenerative brain diseases?

This type of brain disease is caused by slow but progressive degeneration of nerve cells in the brain. Neurodegenerative brain diseases are becoming more common worldwide, partly because of the ageing population and may present as a dementia or as a movement disorder. An example of a movement disorder is Parkinson’s Disease (PD). Alzheimer’s Disease (AD) is a common dementia. However, there are a lot of different dementias and movement disorders, and a correct diagnosis at an early disease phase can be very difficult. A correct early diagnosis is important to be able to start the right management. Furthermore, an accurate diagnosis is important for future scientific research in the field, for example to develop new treatments.

What is an FDG PET scan?

Nerve cells in the brain need energy to function. Due to a disease process, nerve cells may not function properly or start disappearing slowly. This causes a diminished need for energy in the affected part of the brain. The brain regions that show this diminished need for glucose can be different, depending on the disease. Thus, each disease has its own characteristic pattern of diminished energy needs throughout the brain. The energy source of the brain is glucose (a sugar) which together with oxygen is burned into energetic compounds which can be used by the nerve cells. To measure the glucose use of every region in the brain a metabolic imaging system (an ‘FDG PET scan’) can be used. This method is now available in almost all larger medical centers throughout the world.

An FDG PET scan may be ordered by a neurologist when there is uncertainty about the diagnosis. The images of the patient’s FDG PET scan are visually inspected by the nuclear medicine doctor. The neurologist and the nuclear medicine doctor can discuss these images and come to conclusion of which disorder is most likely. However, inspecting the images visually can be quite difficult, especially when a patient has only just started getting symptoms and has minimal changes in the brain. Therefore, special analysis methods need to be applied.

What is the goal of the GLIMPS project?

The main goal of the GLIMPS project is to assist physicians (usually neurologists and geriatricians, but also nuclear medicine physicians) in the correct diagnosis of parkinsonian diseases at an early stage of the disease process.

In the GLIMPS project a complex mathematical formula is used to detect the patterns of abnormal brain metabolism. Mathematically, we are able to detect brain changes that are usually not (yet) visible when we look at individual images. Using this method, we have identified abnormal patterns of brain metabolism for each neurodegenerative disease. We are now able to compare the scan of each individual patient to these patterns. In this way, we are able to calculate if a patient’s scan is compatible with a known pattern of a neurodegenerative disease.

As an example: If a patient is thought to have Parkinson’s disease, but the neurologist is uncertain about the diagnosis because the patient does not respond as expected to therapy, an FDG PET scan may be helpful. The scan is inspected by the nuclear medicine doctor and the neurologist, and they draw their conclusions. In addition, if the patient has given consent for the GLIMPS project, we analyze the scan mathematically as well. We compare the patient’s scan to our known Parkinson’s disease pattern. If the scan shows mathematical similarities to this pattern, and not to the patterns of other neurodegenerative diseases, we conclude that the patient probably has Parkinson’s disease. In this way imaging of brain energy metabolism may contribute to a correct diagnosis early in the disease of neurodegenerative brain diseases. The methods have been shown to work well in preselected groups of patients and we are currently testing the validity of the method in larger groups in clinical practice.

The GLIMPS project is funded by the Dutch Foundation ‘Stichting Parkinson Fonds’

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