Presymptomatic Parkinson's disease: the Arizona experience

There is a growing interest in presymptomatic diagnosis of Parkinson's disease (PD), but the best and most practical method to screen and confirm asymptomatic individuals for PD needs further study. The Banner-Sun Health Brain and Body Donation program in Sun City, Arizona has studied primarily PD and Alzheimer's disease. Enrollees receive annual prospective standardized evaluation that includes clinical, biomarker testing, and at autopsy, neuropathological examination is performed followed by a consensus conference that determines final diagnosis. Since numerous Controls receive these assessments, these subjects become an excellent cohort to study presymptomatic PD. We found that Controls with partial diagnostic criteria for PD (1 of either rest tremor or bradykinesia) had a 6.6 relative risk for eventually developing full diagnostic criteria for PD. Neuropathologic examination has uncovered cases of "incidental Lewy body disease" (ILBD). We have shown that ILBD cases during life demonstrated no significant differences in clinical assessment versus similarly assessed controls. However, electrophysiological assessment showed subclinical low frequency rest discharges in some ILBD cases. Electroencephalography spectral frequency of ILBD cases was lower than for controls but not as low as for PD cases. The longitudinal assessments of this brain bank offer significant opportunities for the study of presymptomatic PD.