Outcome measures
Parkinson’s Disease Questionnaire (PDQ-39).
SECONDARY, COMPLICATIONS, MOS
Per the registered study protocol, the primary outcome was the “Axial-Score” (UPDRS items 13–15; falling unrelated to freezing, freezing when walking, walking; and 27–31; arising from chair, posture, gait, postural stability, body bradykinesia) comparison between Stim-ON and Stim-OFF, in the medication-OFF condition. Axial-Score subscores were also assessed, including Gait-Score (items 13, 14, 15, 29) and Posture-Score (items 27, 28, 30, 31) as posthoc variables (outside of protocol). Secondary outcome measures included UPDRS-I (Mentation, Behavior, and Mood), II (Activities of Daily Living), and IV (Complications of Therapy) in the medication-OFF condition, and UPDRS-III (Motor Examination) in medication-OFF and medication-ON. Additional secondary outcomes included Schwab & England activities of daily living, Hoehn & Yahr Scale, Freezing of Gait Questionnaire (FOGQ), BDI, MMST, Medical Outcomes Study (MOS) Sleep-Scale, and Parkinson’s Disease Questionnaire (PDQ-39). The Axial-Score (medication-ON), Gait-Score (medication-ON), Posture-Score (medication-ON), UPDRS-II (medication-ON), and Gait and Falls Questionnaire (GFQ) scores were acquired and analyzed as additional variables. The study protocol that specified the applied assessments was submitted in 2009. Therefore, an old UPDRS version was applied in subsequent years to remain consistent throughout the study period. Notably, assessments that are conducted by means of a rater or patient self-report only (and not with objective gait analysis measures) may limit the generalizability of the results.