Introduction: Cognitive impairment is incapacitating and deteriorates Parkinson’s Disease patient’s quality of life. The most important brain alteration in PD is progressive nigrostriatal dopamine neurons loss. Animal and human studies have demonstrated that basal ganglia dopamine system is important for cognitive and motor functioning. Dopamine transporter (DAT) PET and SPECT radiotracers have been developed to estimate in vivo human’s dopamine neuronal loss.
Objective: We have used [99mTc]-TRODAT-1 and SPECT to evaluate the relationship of striatal dopamine neuronal loss and several aspects of cognitive performance.
Methods: Thirty subjects (15 PD patients and 15 healthy controls) were scanned with [99mTc]-TRODAT-1 (25mCi) and SPECT (Dual-Head-SPECT Hawkeye, GE). TRODAT-1 kits were donated by INER-Taiwan. SPECT images were reconstructed with FBP and Butterworth filter 0,40c/px order 10. Region interest (ROIs) utilized were striatum (STR) and occipital lobe (BKG non specific binding). ROIS were delimitated in 3 mm transaxials slices analyzed according to this formula BP= ([STR-BKG]/BKG), where BP is the striatal DAT binding potential. Neurocognitive tests were applied to all subjects by trained neuropsychologists, including the Rey Auditory Verbal Learning Test (verbal memory and learning), Wisconsin Card Sorting Test (WCST cognitive flexibility, problem solving and concept formation), Ravens Progressive Matrices, Digit Span (WAIS-III - attention and verbal working memory) and Tavis 3 (selective, sustained and shifting visual attention). This project has been approved in the local and the country’s ethics committee.
Results: Striatal DAT BP was negatively correlated only with the RAVLT tests 4 (p<0.05, R= 0.57) and 5 (p<0.05, R= 0.57), which evaluate verbal learning. Striatal DAT BP was also negatively with the WCST learning item (p<0.05, R=0.54) and the Tavis 3 items, action error (p<0.05, R=0.52) and assert number (p<0.05, R=0.47).
Conclusions: These preliminary results suggest that striatal DAT loss is associated poorer performance in verbal learning and cognitive flexibility tests. These results agree with a previous study in healthy volunteers showing that high DAT density in the caudate correlated with good performance verbal learning tasks. Caudate/putamen segmentation in a larger sample is being implemented and will provide more information on cognitive deficits and DAT loss.
