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.
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