Parkinson’s disease affects one in every hundred people over the age of 60. Until recently, however, doctors had to rely on a clinical evaluation, combined with blood tests and brain studies, to diagnose this common movement disorder. But the results were often inconclusive because there was no test to distinguish Parkinson’s disease (PD) and related disorders from other conditions that have similar symptoms. As a result, effective treatment could sometimes be delayed while the patient and physician searched for answers.
Now, a recently introduced nuclear imaging test called DaTscan is helping specialists at Orange Coast Memorial evaluate patients with suspected parkinsonian syndromes, of which PD is the most common. The test is especially important because it helps distinguish PD and allied disorders from a look-alike condition called essential tremor—a disorder characterized by trembling of the hands, head, and occasionally the arms and legs. “Although Parkinson’s disease and essential tremor both involve involuntary shaking movements that are similar, these disorders require very different treatments,” says Daniel Truong, M.D., a internationally known neurologist and medical director of The Parkinson’s and Movement Disorder Institute at Orange Coast Medical Center. “DaTscan allows us to rule out essential tremor and other non-parkinsonian conditions, which can help lead to a more accurate and timely diagnosis and treatment.”
Before DaTscan, a correct diagnosis for patients with suspected PD could take up to six years. But the new test, in combination with other evaluations, can help reduce the diagnostic process to weeks.
Here’s how it works: DaTscan involves single-photon emission computerized tomography, or SPECT—a type of nuclear imaging test. During the study, a radiopharmaceutical solution, or tracer, is injected through an IV into the patient’s bloodstream. Then a special gamma camera takes 3-D pictures of the brain to assess the patient’s dopamine system, of which the dopamine transporter (DaT) is a component. Dopamine is a chemical that’s essential in controlling movement and other muscle functions.
DaTscan shows changes in brain chemistry, including a deficiency of dopamine—a sign of PD and other parkinsonian disorders. This sets PD and related conditions apart from essential tremor.
“Patients with PD typically begin to experience symptoms of the disease after losing 80 percent of the dopamine in their basal ganglia, the region of the brain involved in motor control and movement,” says Truong. “Often, the initial symptoms of the disease are vague, making diagnosis extremely challenging. DaTscan is a step in the right direction. It assists doctors in differentiating between movement disorders that share PD-like symptoms.”
Dr. Truong notes that DaTscan imaging tests should be performed only by specialists who have done a high volume of Parkinson’s disease scans. “Experience is a key factor to accurately interpreting these imaging results,” he explains.
The test has been available for more than 10 years in Europe, where nearly 300,000 patients in 32 countries have undergone DaTscan evaluation. “The U.S. Food and Drug Administration recently approved DaTscan for use in this country,” says Truong. “It is the first diagnostic imaging technique approved by the FDA for evaluation of PD and other parkinsonian movement disorders.”
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