Progression of Parkinsonian Signs in Parkinson Disease

Abstract
CLINICIANS HAVE long appreciated the progressive nature of Parkinson disease (PD),1 and it is generally accepted that extrapyramidal signs (EPSs), particularly parkinsonian signs, increase in severity over time. Current knowledge about the rate of progression of EPSs in PD is largely inferred from cross-sectional studies2-4 comparing subjects with different disease durations at one point. There are few longitudinal studies in which the subjects are followed up over time,5,6 and the emphasis of these studies has been on treatment issues rather than the rate of progression of EPSs. Little is known about the specific factors that influence the rate of progression of EPSs in PD.