Clinical correlates of {18F}fluorodopa uptake in five grafted Parkinsonian patients

Abstract

To assess the efficacy of fetal mesencephalic grafts in Parkinson's disease, it is important to know if the grafted cells survive and are functional. Positron emission tomography (PET) and {¹⁸F}fluorodopa ({¹⁸F}dopa) have been used to demonstrate the survival of the grafted cells, but the relationship of {¹⁸F}dopa uptake changes in the grafted striatum to motor function remains unclear. We investigated this question with 16 serial PET scan in 5 severe parkinsonian patients unilaterally grafted in whom we found a significant and progressive increase of the {¹⁸F}dopa uptake in the grafted putamen. The number of patients was too small to assess the sensitivity of {¹⁸F}dopa PET scans in individual patients. Yet, by analyzing the 16 serial PET scans we found a correlation between the {¹⁸F}dopa uptake (K_i) in the grafted putamen and the percentage of daily time spent “on,” suggesting that K_i changes have a functional meaning. In addition, the K_i values were correlated with the contralateral finger dexterity to the same extent in both the grafted and nongrafted putamen. These results indicate that {¹⁸F}dopa uptake reflects the motor function of the opposite side of the body, similarly in the grafted and ungrafted putamen, at least in terms of these tasks. Finally, extrapolating from these correlations offers the suggestion that clinical optimal results of the graft could be achieved if the graft brings the K_i values in the putamen to about two standard deviations of mean control values.