Impact of subcortical white matter lesions on dopamine transporter SPECT

Subcortical arteriosclerotic encephalopathy (SAE) can affect the nigrostriatal system and presumably cause vascular parkinsonism (VP). However, in patients with SAE, the differentiation of VP from idiopathic Parkinson's disease (IPS) is challenging. The aim of the present study was to examine the striatal dopamine transporter (DAT) density in patients with parkinsonism and SAE. Fifteen consecutive patients with parkinsonian symptoms displayed SAE, as detected by magnetic resonance imaging (MRI). Fifteen retrospectively chosen, matched patients with diagnosis of IPS without any abnormalities in MRI served as a reference group. DAT SPECT was performed using the tracer ¹²³I-FP-CIT. Scans were acquired on a triple-head SPECT system (Multispect 3, Siemens) and analysed using the investigator-independent BRASS™ software (HERMES). In the SAE group, a DAT deficit was observed in 9/15 patients. In contrast, all patients from the IPS group showed a reduced DAT binding (p = 0.008). The specific binding ratios (BR) of putamen contralateral to the side of the more affected limb versus occipital lobe were in trend higher in patients with SAE versus patients in the IPS-group (p = 0.053). Indices for putaminal asymmetry (p = 0.036) and asymmetry caudate-to-putamen (p = 0.026) as well as the ratio caudate-to-putamen (p = 0.048) were significantly higher in IPS patients having no SAE. DAT deficit was less pronounced in patients with SAE and parkinsonism than in patients with IPS without any abnormalities in the MRI. A potential role of DAT SPECT in the differential diagnosis of VP and IPS requires more assessments within prospective studies.