Symptomatic characteristics of parkinsonism and the width of substantia nigra pars compacta on MRI according to ischemic changes in the putamen and cerebral white matter: implications for the diagnosis of vascular parkinsonism

Abstract

To investigate the significance of vascular lesions as a cause of secondary parkinsonism, we analyzed the symptomatic characteristics, the width of the substantia nigra pars compacta (SNpc) on MRI and the responsiveness to L-dopa in 227 parkinsonian cases, excluding those with drug-induced parkinsonism and neurodegenerative diseases other than idiopathic Parkinson's disease (IPD). They were classified into those without a significant infarct in the basal ganglia (n = 144), those with status lacunaris in the putamen (SLP; n = 66) and those with confluent white matter hyperintensity signals (CWMH; n = 17). The 4- to 6-Hz tremor and cogwheel rigidity were significantly more frequent in cases without significant infarct (69%) than those with SLP (50%) and those with CWMH (12%; p < 0.05). Among cases with 4- to 6-Hz tremor and cogwheel rigidity, the frequency of patients with a reduced SNpc width and L-dopa responders did not significantly differ between those with SLP (73 and 83%, respectively) and those without significant infarct (83 and 86%, respectively), suggesting that the diagnosis for most of these cases would be probable IPD. In contrast, among cases without 4- to 6-Hz tremor and cogwheel rigidity, those with a reduced SNpc width or L-dopa responders were significantly less frequent among cases with SLP (25 and 38%, respectively) than among those without significant infarct (75 and 71%, respectively; p < 0.05). Patients with neither 4- to 6-Hz tremor and cogwheel rigidity nor reduction in the SNpc width, for whom the probable diagnosis was vascular parkinsonism (VP), were significantly more frequent in cases with SLP (26%) and with CWMH (40%) than those without significant infarct (8%), accounting for 10.6% of the total parkinsonian cases. These findings suggest that parkinsonian cases with SLP or CWMH consist of not only cases with vascular-lesion-related VP but also IPD in which vascular lesions are not directly related to parkinsonism. Absence of 4- to 6-Hz tremor, cogwheel rigidity and the reduction in the SNpc width could be indicators for differentiating VP from IPD.