Fig. 6.

Necessary sample size per treatment arm using PBVC, VIENA, global cognitive decline in PD-MCI. Calculations were performed on the assumption of a treatment effect corresponding to 20%–50% reduction in the decline of the outcome measure, at 80% power, and a 2-sided 0.05 level of significance. Abbreviations: PBVC, percentage brain volume change; PD-MCI, Parkinson's disease with mild cognitive impairment; VIENA, ventricular enlargement.