Researchers report on the first objective diagnostic test for Parkinson’s disease – a brain function imaging agent that allows SPECT scans to depict dopamine activity in the brain and will be trialed at 14 medical centers, which are enrolling now.
Parkinson’s disease, a type of nerve degeneration associated with loss of dopamine in the brain, involves gradual development of serious tremors, stiffness, and balance problems, and claims some 60,000 new cases each year in the US.
Unfortunately, diagnosis of PD has been notoriously hard to pin down versus other movement disorders such as essential tremor (which require different treatments). In fact, examinations early on can be inconclusive or lead to misdiagnosis of another movement disorder, and doctors have not even been able to say with certainty that those enrolled in Parkinson's studies have the disease, says Tanya Simuni, MD, a neurologist at Northwestern Memorial Hospital’s Parkinson's Disease and Movement Disorders Center. So diagnosis can take up to 6 years.
This is because "in Parkinson's patients the brain's anatomy remains largely normal, unlike other conditions such as stroke, where damage to the brain is visible," she explains.
But now, thanks to a new diagnostic imaging technique that Dr. Simuni and her team are employing at Northwestern, there is an objective test to evaluate patients for “Parkinsonian syndromes,” such as Parkinson's disease. Northwestern is among the first institutions in the country to offer DaTscan™, the only FDA-approved imaging agent for assessment of movement disorders.
"The scan by itself does not make the diagnosis of Parkinson's but it allows us to identify patients who have loss of dopamine, the major chemical responsible for the symptoms, from those who have no dopamine deficiency," says Dr. Simuni, MD. "This is a very important step in being able to accurately identify and treat movement disorders and hopefully allow us to better understand these diseases over time."
Developed by GE Healthcare, DaTscan is a substance used to detect the presence of dopamine transporters (DaT) in the brain. A patient is injected with the contrast agent and then undergoes a single-photon emission computed tomography (SPECT) scan.
The test captures detailed pictures of the brain's dopamine system and can provide visual evidence of the presence of dopamine transporters.
• Scans of patients with Parkinson's disease or another parkinsonian syndrome will show very low dopamine levels.
• A SPECT scan examines brain function, rather than structure, and can show change in the brain's chemistry.
• The injected "DaTscan attaches to dopamine neurons which illuminate on the SPECT scan,” says Dr. Simuni. “The more light areas that exist, the more healthy dopamine brain cells remain.
• If the areas of the brain that should show dopamine remain dark, it may indicate the patient has some type of parkinsonian syndrome."
"We are hopeful that this will lead to improved quality of life for these patients with better long term outcomes, as well as protection from unnecessary treatments initiated because of misdiagnosis," says Dr. Simuni.
And while she does not believe it is necessary for every patient to confirm their Parkinson's diagnosis with DaTscan, she does see it as a valuable tool for patients with uncertain syndromes, or those who have not responded to treatment. She also sees it as a means for improving Parkinson's research by ensuring those enrolled in studies actually have the disease.
DaTscan is already being used by the Michael J. Fox Foundation for its landmark biomarkers study - the Parkinson's Progression Markers Initiative (PPMI) - to validate that the subjects have Parkinson's disease. Northwestern is one of the 14 U.S. medical centers enrolling for the PPMI, which is among the first clinical trials using DaTscan in this way.
Source: Northwestern Memorial Hospital (Chicago) news release, Aug 25, 2011