NEW YORK – Making the clinical diagnosis of dementia in Parkinson’s patients has been confounding because of the difficulty of differentiating it from dementia in Alzheimer’s disease, but researchers have developed a novel imaging technique, known as single-scan dynamic molecular imaging, which uses positron emission tomography to identify the key differentiating factor between the two types of dementia, as reported at the International Conference on Parkinson’s Disease and Movement Disorders.
“We have a technique with which we can detect neurotransmitters in the brain, particularly in patients with dementia,” said, professor of psychiatry at the Icahn School of Medicine at Mount Sinai in New York. “This is important to not only understand the type of dementia you’re dealing with but also to understand the underlying neurocognitive problem.”
The technique is called single-scan dynamic molecular imaging technique (SDMIT) and uses PET to detect and measure dopamine release activity in the brain during cognitive or behavioral functioning, he said. After patients are placed in the PET scanner, they receive an IV injection of the radio-labeled ligand fallypride. While in the PET scanner, patients are asked to perform a cognitive task, and PET measures the ligand concentration before and after the task in the dorsal striatum of the brain. The rate of ligand displacement before and after the task are compared to determine the levels of dopamine activity in the brain.
A significant dysregulation of dopaminergic neurotransmission would indicate a diagnosis of Parkinson’s dementia, while dysregulation of acetylcholine neurotransmission is characteristic of Alzheimer’s dementia, Dr. Badgaiyan said.
He described the experimentation that went into developing SDMIT, including its use in patients with ADHD and how the technique evolved from obtaining two PET scans to measure dopamine levels. His research also found that fallypride was the most effective ligand because it has a high affinity for the dopamine-2 receptor.
“The bottom line is that this technique can be used to study those conditions that are dopamine dependent” Dr. Badgaiyan said. “We can also use this technique to study the neurocognitive basis of the clinical symptoms in dementia and other cognitive deficits.”
SDMIT can also help to identify novel therapeutics targets for dementia, he said. “Today there is no medication that can reverse dementia; all the drugs that we use can only reduce the progression,” he said. “But this technique can help us identify which area of the brain should be targeted and what symptoms should be targeted to reverse dementia, treat dementia, or to cure dementia.”
Dr. Badgaiyan disclosed receiving funding for his research from the National Institutes of Mental Health, Department of Veterans Affairs, the Dana Foundation and Shriners Foundation.