(123I) β-CIT and single-photon emission computed tomographic imaging vs clinical evaluation in Parkinsonian syndrome -: Unmasking an early diagnosis

Background: The diagnosis of Parkinson disease is currently based on clinical evaluation. Functional neuroimaging using (I-123) P-carboxymethyoxy-3-beta-(4-iodophenyl) tropane (CIT) and single-photon emission computed tomography (SPECT) provides information on the integrity of the dopaminergic system in vivo and is a promising diagnostic tool in early Parkinson disease. Objective: To evaluate the diagnostic accuracy of dopamine transporter imaging using (I-123)beta-CIT in patients with suspected parkinsonian syndrome (PS). Design: Community neurologists referred patients with suspected PS for imaging evaluation. Clinical diagnoses (positive PS or negative PS) were provided by the community neurologists and 2 movement disorder experts. We performed (I-123) beta-CIT and SPECT imaging, and imaging diagnoses of positive PS or negative PS were assigned. A 6-month follow-up clinical diagnosis was assigned by a movement disorder expert blind to the imagingdata, which represented the "gold standard" diagnosis for the study. Results: Thirty-five patients with suspected PS were referred. Diagnoses in question included essential tremor, psychogenic parkinsonism, drug-induced parkinsonism, primary dystonia, and unspecified gait disorder. Comparing the community neurologist's diagnoses at referral with the gold standard diagnosis, there was disagreement in 25.7% (sensitivity, 0.92; specificity, 0.30). Comparing the quantitative imaging diagnoses with the gold standard, there was disagreement in 8.6% (sensitivity, 0.92; specificity, 1.00). Conclusion: Performing (I-123)beta-CIT and SPECT imaging at baseline appears to be a useful diagnostic tool to detect patients thought to have PS at baseline but who, after follow-up, do not have PS.