Regional cerebral blood flow in Parkinson's disease as an indicator of cognitive impairment

Objective To investigate the pattern of regional cerebral blood flow (rCBF) deficits in Parkinson's disease patients in relation to cognitive decline and to assess the clinical usefulness of single photon emission tomography (SPET) scanning in differentiation between Parkinson's disease patients with dementia and those without cognitive deficits. Methods We performed Tc-99m-ECD SPET in 60 patients with idiopathic Parkinson's disease (F: 25, M: 35), with average age of 68.4 years (SD +/- 7.3, range 51-81 years). All patients were examined neurologically with the assessment of stage and severity of Parkinson's disease (Hoehn-Yahr scale, UPDRS, Schwab-England scale). Detailed neuropsychological examination was performed in each Parkinson's disease patient. On the basis of DSM-IV criteria of dementia and the results obtained in psychological examination, the whole group was divided into three subgroups: I, with no cognitive changes (n=17 II, with mild cognitive impairment (n = 25); and III, with dementia (n=18). Results There was noticeable significant decrease of perfusion in all areas in Parkinson's disease patients when compared to the age-matched control group of healthy volunteers (n = 20). In group III, perfusion was significantly decreased (when compared to groups I and II), particularly in parietal and temporal areas with the predominance of the left side. Regression analysis revealed two independent factors related to dementia: decrease of perfusion within left temporal lobe and its increase within left thalamus. Conclusion Parkinson's disease patients with dementia showed left temporo-parietal hypoperfusion as compared to a group of patients without dementia, which resembles perfusion deficits described in Alzheimer's disease. The hypoperfusion of the left temporal lobe with increase of rCBF within the left thalamus might be clinically useful in discrimination of Parkinson's disease patients with dementia against those without cognitive impairment.