The new technology is the first and only FDA-approved test that helps differentiate Parkinson from Essential Tremor Syndromes
For decades, doctors have relied largely on a keen eye and experience to diagnose Parkinson's disease.
Now the pairing of a new drug and a high-tech nuclear brain scan is offering long-awaited help in the early diagnosis of Parkinson’s disease (PD). A progressive movement disorder, PD is primarily diagnosed through clinical examinations, with neither a specific diagnostic test nor a cure.
“That’s what makes this test so important,” said Dean Sutherland, MD, PhD, a Sarasota neurologist who specializes in Parkinson disease. “Clinical exams alone, particularly early in the disease, are often inconclusive and proper diagnosis can be delayed for years.”
Prior to the test, an accurate diagnosis for patients with neurodegenerative movement disorders, such as PD, could take up to six years. PD, which currently affects one million people in the US, is one of several types of Parkinson syndromes (PS). The challenge for physicians is how to differentiate Parkinsonian syndromes from other conditions that mimic it, such as essential tremor. While the symptoms are similar, treatment and management greatly differ.
Having another diagnostic tool to help rule out one of these conditions is helpful in reaching an accurate and early diagnosis for patients. “Early diagnosis is essential,” Sutherland said, “because we now know that early intervention has a positive impact on quality of life for years to come.”
PS occurs when the brain does not get enough dopamine to perform certain functions. This affects the ability of the brain to control movement and other muscle functions. The new technology, called DaTscan, shows if and where a dopamine deficiency is occurring, using an injected drug – a small radioactive molecule of iodine attached to ioflupane – and a type of brain imaging known as single photon emission computed tomography (SPECT). The radiopharmaceutical imaging agent works by binding to dopamine transporters (DaT) in the brain. The scan produces images that provide visual evidence based on the density of dopamine transporters.
The nuclear medicine procedure has been done in Europe for the past decade, but was only approved by the FDA for use in the United States last year. Sarasota Memorial started offering the procedure in October 2011, becoming the fifth testing site in Florida and one of only 154 nationwide. The hospital screened 55 patients in the first three months – 34 cases confirmed a PD diagnosis, 19 cases were normal and two more were pending at the time of this report.
Although positive results can be sobering for those diagnosed, Sutherland said, the test results are about 95 percent accurate, and in the end, many welcome the clarity. Parkinson’s medications can have significant side effects, and sometimes doctors hesitate to prescribe them to people until they can eliminate the possibility of essential tremor or other movement disorders.
"Remaining in diagnostic limbo may mean a lack of treatment and information at a critical time in the patient's disease and in their life, and that uncertainty can be all-consuming for some people,” Sutherland said. “Very good studies in Europe and the U.S. show that tremors are misdiagnosed in 25 percent of cases, even by neurologists who specialize in movement disorders. Imagine if you were on Parkinson medication for 5 years only to find out that you didn't have it!"
The scan is available by referral from Sarasota Memorial’s neurologists. For patient information, please call Nuclear Medicine lab at (941) 917-7243.