Arpin DJ, Mitchell T, Archer DB, et al. - Findings demonstrate absence of a disease-modifying effect of 1 mg/day rasagiline in Parkinson disease (PD) over 1 year. During the same time period, an increase in posterior substantia nigra (pSN) free-water was observed, and there was a correlation between baseline free-water and clinical motor progression, showing that diffusion imaging parameters hold significance for identifying as well as predicting PD progression.

• A prospective, randomized, double-blind, placebo-controlled trial to determine the impacts of rasagiline given at 1 mg/day over 12 months in early-stage PD patients.

• One-year change in free-water accumulation in pSN was recorded employing two diffusion magnetic resonance imaging pulse sequences, one with a repetition time (TR) of 2,500 ms (short TR; n = 90) and one with a TR of 6,400 ms (long TR; n = 75).

• No significant difference in absolute change in pSN free-water accumulation was observed between groups (short TR: P = 0.346; long TR: P = 0.228).

• Long TR, but not short TR, data demonstrated significant increase in pSN free-water over 1 year (P = 0.025).

• Over 1 year, there was a significant increase in Movement Disorder Society Unified Parkinson's Disease Rating Scale testing of motor function, Part III.