Differentiating vascular parkinsonism from idiopathic Parkinson's disease: a systematic review.

Vascular parkinsonism (VP) remains a loose constellation of various clinical features. We systematically reviewed studies comparing clinical, neuroimaging and other investigations that might distinguish VP from idiopathic Parkinson's disease (PD). Medline, Embase, Cinahl (R), and PsycINFO were searched by querying appropriate key words. Reports were included if the study population contained comparative findings between patients with VP and PD. Twenty-five articles fulfilled the selection criteria. Patients with VP were older, with a shorter duration of illness, presented with symmetrical gait difficulties, were less responsive to levodopa, and were more prone to postural instability, falls, and dementia. Pyramidal signs, pseudobulbar palsy, and incontinence were more common in VP. Tremor was not a main feature of VP. Structural neuroimaging was more likely to be abnormal in VP (90-100% of cases) than in PD (12-43% of cases), but there was no specific abnormal structural imaging pattern for VP. Two studies of presynaptic striatal dopamine transporters (using single photon emission computed tomography) showed a significant reduction in striatal uptake ratios in PD but not in VP, whereas another study found that only the mean asymmetry index was significantly lower in VP. Various other investigations, including alternative imaging techniques, electrophysiological, and neuropsychological studies, are reported, but the diverse diagnostic criteria used makes it difficult to reach any firm conclusions. The development of accepted international diagnostic criteria for VP is urgently needed to facilitate further studies.