Imaging agent may reveal which tremors are caused by Parkinson’s disease

Approximately 1.5 million people in the US have Parkinson’s disease, and as many as 10 million others are afflicted by essential tremor, a condition that often is confused with Parkinson’s. According to a 2002 report in the European Journal of Neurology, there is a 20 to 30 percent misdiagnosis rate in the early stages of Parkinson’s disease. Now Dr. Mark Pykett and his colleagues at Boston Life Sciences Inc. in Hopkinton, Mass., have tested whether the company’s molecular imaging agent, Altropane, can distinguish between tremors caused by Parkinsonian syndrome and those associated with other disorders more accurately than clinical diagnoses from physicians.

The imaging agent binds to the dopamine transporter protein found on the surface of dopamine-producing neurons, making it visible during single-photon emission computed tomography. Because most Parkinsonian syndromes usually result in a decreased number of dopamine-producing cells, the researchers believed that patients with these syndromes also would have fewer dopamine transporter proteins. Therefore, they hypothesized that the agent would enable them to see whether tremors are associated with Parkinsonian diseases or with the other disorders.

A primary care physician first evaluated patients with tremors and judged whether the tremors were related to Parkinson’s disease. The patients then underwent scans — utilizing the imaging agent — and these scans were evaluated by imaging experts who were blind to the patients’ clinical data. Finally, a movement disorder specialist — whose diagnosis was considered the gold standard for the study — determined which of the patients had Parkinson’s disease. The scans showed statistically significant superiority over the nonspecialist physicians’ clinical evaluations in distinguishing the cause of tremors.

The researchers believe that the imaging agent will enable physicians to provide more informed prognoses for their patients earlier as well as to prescribe effective treatments.