[^99mTc]-HM-PAO SPECT in Parkinson's Disease

Abstract

Thirty-six patients affected by Parkinson's disease were studied using single photon emission computed tomography (SPECT) and [99mTc]–HM-PAO as a tracer. The scanning procedure was performed 16–24 h after discontinuation of specific therapy. Tracer activity ratios were determined in 10 pairs of cerebellar, cortical, and subcortical regions. Data were compared with those of 10 age-matched controls. Most of the regions examined did not show any relevant change between parkinsonian and control subjects. Notably, mean activity in striatal regions were similar in the two groups. Increased activity in caudate–putamen was found in patients who were on chronic DOPA therapy. Side-to-side asymmetries in the basal ganglia increased with the severity of the disease. Significant reductions of tracer uptake, from control values, were observed bilaterally in the parietal cortex. These deficits were more pronounced in patients with mental deterioration and in subjects who had been chronically treated with anticholinergic drugs. Parietal perfusion deficits in parkinsonian patients resemble those described in Alzheimer's dementia. These findings suggest that the heterogeneous alterations of regional cerebral blood flow (rCBF) in parkinsonian patients reflect the multifactorial pathophysiology of the disease.

N-isopropyl-p-123I Iodoamphetamine Single Photon Emission Computed Tomography Study of Parkinson's Disease with Dementia

“…Although frontal lobe dysfunction has been described clinically in Parkinson's disease (17)(18)(19)(20)(21)(22)(23), there has not been any significant frontal hypoperfusion observed either in our population or in other studies (8,11).…”

“…Sawada et al used 123 I-IMP to divide Parkinson's disease patients with dementia into two groups based on those demonstrating frontal hypoperfusion and those demonstrating frontal and parietal hypoperfusion (27). Using 99 mTc-HMPAO, Pizzolato et al found parietal hypoperfusion in Parkinson's disease patients with a low MMSE score (8). Yamamoto reported that frontal, parietal and occipital hypoperfusion was detected in Parkinson's disease patients with dementia using 123 I-IMP SPECT (28).…”

“…Although there is general agreement that a global reduction in rCBF and metabolism predominantly affecting the parieto-temporal regions is encountered in Alzheimer's disease, the available data in Parkinson's disease are conflicting, and do not demonstrate distinctions in specific patterns of rCBF or metabolism between Parkinson's disease with or without dementia (8)(9)(10)(11). One of the reasons may be that many factors contribute to the pathophysiology of dementia in Parkinson's disease, such as Alzheimer's disease-like mechanism, diffuse Lewy body disease-like factor or frontal dysfunction due to Parkinson's disease itself.…”

Cerebral Blood Flow in Parkinson’s Disease, Dementia with Lewy Bodies, and Alzheimer’s Disease according to Three-Dimensional Stereotactic Surface Projection Imaging

“…Globus et al [1] suggested that a reduction in cortical blood flow and intellectual deterioration may be caused by different mechanisms, as they found no correlation between the severities of these changes. On the other hand, by SPECT using 99m Tc-hexamethylpropyleneamine oxime, Pizzolato et al [3] demonstrated parietal perfusion deficits in demented parkinsonian patients. Kuhl et al [33] observed bilateral cortical hypometabolism, most marked in the posterior parietal areas, in a group of subjects with PD who varied from nondemented to severely demented.…”

“…Another reason for the inconsistency may be the lack of standardization of image analysis methods. In most previous studies, visually placed regions of interest (ROI) were analyzed to determine alterations in rCBF [1][2][3]11]. Manual placement of ROI in this approach can give rise to observer biases and leave large areas of the brain unexplored.…”