Vascular Parkinsonism: deconstructing a syndrome

Abstract

Progressive ambulatory impairment and abnormal white matter (WM) signal on neuroimaging come together under the diagnostic umbrella of vascular parkinsonism (VaP). A critical appraisal of the literature, however, suggests that (1) no abnormal structural imaging pattern is specific to VaP; (2) there is poor correlation between brain MRI hyperintensities and microangiopathic brain disease and parkinsonism from available clinicopathologic data; (3) pure parkinsonism from vascular injury ("definite" vascular parkinsonism) consistently results from ischemic or hemorrhagic strokes involving the SN and/or nigrostriatal pathway, but sparing the striatum itself, the cortex, and the intervening WM; and (4) many cases reported as VaP may represent pseudovascular parkinsonism (e.g., Parkinson's disease or another neurodegenerative parkinsonism, such as PSP with nonspecific neuroimaging signal abnormalities), vascular pseudoparkinsonism (e.g., akinetic mutism resulting from bilateral mesial frontal strokes or apathetic depression from bilateral striatal lacunar strokes), or pseudovascular pseudoparkinsonism (e.g., higher-level gait disorders, including normal-pressure hydrocephalus with transependimal exudate). These syndromic designations are preferable over VaP until pathology or validated biomarkers confirm the underlying nature and relevance of the leukoaraiosis. © 2015 International Parkinson and Movement Disorder Society.

Keywords: higher-level gait disorder; normal-pressure hydrocephalus; vascular parkinsonism; white matter ischemic disease.

Figure 1. Brain MRI in case of suspected vascular parkinsonism

Axial fluid-attenuated inversion recovery brain MRI of 80-year-old man with hypertension, hypercholesterolemia, and a 60 pack/year accumulated smoking history. Increased periventricular and subcortical white matter signal is suggestive of small-vessel ischemic disease. Ventricular dilatation appeared roughly proportionate to the assessment of parenchymal atrophy. However, apical cuts (lower row) did not support generalized atrophy. Increased signal intensity affecting subcortical and periventricular white matter suggested chronic small-vessel ischemic disease. Pathology showed normal brain weight, no micro- or macroangiopathy, and instead revealed changes consistent with normal pressure hydrocephalus.

Figure 2. No parkinsonian sequelae in classic vascular injury syndromes

A. Axial diffusion weighted brain MRI exemplifying acute stroke syndromes (clockwise from upper left): complete and partial middle cerebral artery [MCA] territory, exclusively in the caudate and putamen, and small infarcts in different vascular distributions (embolic etiology). B. Head CT of selected traumatic brain injury-associated vascular injury syndromes. Upon recovery, none of these patients manifested parkinsonism. Images courtesy of Drs. Achala Vagal (University of Cincinnati; panel A) and Alisa Gean (University of California, San Francisco; panel B).

Figure 3. Anatomical patterns in “vascular parkinsonism”

Vascular pseudoparkinsonism arises in the context of bilateral mesial frontal strokes due to anterior cerebral artery territory infarcts (A, akinetic mutism); bilateral striatal lacunar infarctions (B, apathetic depression); or small-vessel ischemic disease affecting the pons (C, pyramidal weakness and slowness). Pseudovascular pseudoparkinsonism occurs in the context of periventricular and deep white matter signal abnormalities in isolation (D, higher-level gait disorder) or in association with ventriculomegaly (E, higher-level gait disorder in normal pressure hydrocephalus). Pseudovascular parkinsonism can be documented in patients with Parkinson’s disease (with a pattern similar to D) or progressive supranuclear palsy (F, arrow point to atrophic midbrain). This diagrammatic representation does not include mixed-pathology parkinsonism (e.g., Parkinson’s disease with true microangiopathic brain disease), presumably accounting for a minority of patients with “vascular parkinsonism.”