ASSESSMENT OF DISEASE SEVERITY IN PARKINSONISM WITH FLUORINE-18-FLUORODEOXYGLUCOSE AND PET

Fluorine-18-fluorodeoxyglucose (FDG) and PET have been used to identif y an abnormal regional metabolic covariance pattern in Parkinson's dis ease (PD). To examine the potential use of this covariance pattern as a metabolic imaging marker for PD, we describe the Topographic Profile Rating (TPR), which is a method for calculating subject scores for th is pattern in individual PD patients. We then assess the relationship between these metabolic measures and objective independent disease sev erity ratings. Methods: Two independent groups of PD patients were stu died with FDG-PET. Group A consisted of 23 patients (mean age 60.2 +/- 12.2; mean Hoehn and Yahr stages 2.4 +/- 1.3) and Group B had 14 pati ents (mean age 49.0 +/- 12.1; mean Hoehn and Yahr stage 3.2 +/- 1.2). The regional cerebral metabolic rates for glucose (rCMRGlc) in all pat ients in each group were measured. TPR was used to calculate subject s cores for the disease-related covariance pattern on a patient-by-patie nt basis. Results: In both PD patient groups, subject scores correlate d with Hoehn and Yahr disease severity ratings (Group A: r = 0.59, p < 0.004; Group B: 0.57, p < 0.04), quantitative ratings for bradykinesi a (Group A: r = 0.63, p < 0.002; Group B: r = 0.61, p < 0.03), rigidit y (Group A: r = 0.59, p < 0.004; Group B: r = 0.59, p < 0.04), but not with tremor. Conclusion: These findings indicate that regional metabo lic covariance patterns are robust imaging markers of disease severity . FDG-PET may be useful clinically in assessing parkinsonian disabilit y and disease progression.