High Prevalence of Early Parkinson's Disease in Patients With Subtle Parkinsonian Signs.

Little is known about how frequently patients with a Unified Parkinson Disease Rating Scale part III (UPDRS-III) score of 3 or 4, including postural and action tremor, could be classified into early Parkinson's disease (PD). To examine the prevalence of early PD in patients with subtle parkinsonian signs (rest tremor, postural tremor, and rigidity) without bradykinesia, having a UPDRS-III score of 3 or 4. Parkinsonism was assessed using UPDRS-III based on both the United Kingdom PD Society Brain Bank criteria and the Movement Disorder Society PD criteria. Ninety patients with a UPDRS-III score of 3 or 4, including postural tremor, were evaluated by I-FP-CIT SPECT (DaTscan), brain MRI, the Mini-Mental State Examination, and smell test. Some patients were additionally examined by I-metaiodobenzylguanidine myocardial scintigraphy or I-N-isopropyl-p-iodoamphetamine SPECT. Seventy-five [mean age (standard deviation): 76.9 (8.1)] out of 90 patients (83.3%) showed abnormal findings on DaTscan imaging: 57 out of 75 (76.0%) showed a reduced specific binding ratio (SBR) accompanied by an egg shape pattern ( = 37, 49.3%) or a mixed type pattern ( = 14, 18.7%), both reduced SBR and increased asymmetry index (AI) with a normal shape ( = 4, 5.3%), and reduced SBR only ( = 2, 2.7%); 18 (24.0%) showed an egg shape pattern or a mixed type pattern without reduced SBR. In other words, 69 out of 75 patients (92.0%) showed either an egg shape or a mixed type pattern with or without reduced SBR. All patients were free of dementia, and their olfactory function was significantly impaired compared with controls ( = 141) on the odor-stick identification test for Japanese ( < 0.0001). The prevalence of patients with subtle parkinsonian signs having a UPDRS-III score of 3 or 4, including postural tremor, is unexpectedly high in daily clinical practice, and most of these patients could be categorized into mild early-stage PD.