Clinical and [18F] dopa PET findings in early Parkinson's disease.

Twenty seven patients with recent onset (mean symptom duration 22 (SD 14) months, Hoehn and Yahr score 1.8 (SD 0.7)) Parkinson's disease were studied with [18F]dopa PET. There was a correlation between putamen influx (Ki) and clinical rating, but not symptom duration. In 11 patients with hemi-Parkinson's disease of recent onset there were significant differences between normal (mean 0.0123 (SD 0.0023)), asymptomatic (mean 0.0099 (0.0020)) and symptomatic (mean 0.0070 (00.014)) putamen Kis. This suggests that Parkinson's disease has a widely variable rate of progression, and is most compatible with a short preclinical period. Symptom onset was estimated at a putamen Ki of between 57% and 80% of normal. Most ipsilateral putamen Ki values in early asymmetric Parkinson's disease fell within the normal range. The implication is that either the disease is not established in the ipsilateral putamen or that the technique is insufficiently sensitive to detect it. Discriminant analysis completely separated the normal and Parkinson's disease cohorts, but when a discriminant function from a previous study was used predictively four of the 27 patients with Parkinson's disease were incorrectly classified as normal.