NoMoFa as a new tool to evaluate the impact of deep brain stimulation on non-motor fluctuations: A new perspective

Background: Non-motor symptoms and non-motor fluctuations (NMF) in Parkinson's disease (PD) strongly affect health-related quality of life (HRQoL) and disability. The impact of deep brain stimulation (DBS) on NMF remains an area of uncertainty. The aim is to evaluate the impact of DBS on NMF, using the recently validated Non-Motor Fluctuation Assessment (NoMoFa), and to explore the correlation between NMF and motor symptoms, motor complications (MC), and HRQoL post-surgical improvement. Methods: We prospectively evaluated consecutive patients undergoing subthalamic DBS (STN-DBS), at baseline and 6-months after surgery. Assessments included the NoMoFa questionnaire, the MDS-sponsored Unified Parkinson's Disease Rating Scale, and the 39-Item Parkinson's Disease Questionnaire. Pre- and post-surgical NoMoFa scores were compared using the Wilcoxon Signed rank-test. Linear regression analysis evaluated: a) the correlation between NoMoFa scores, motor and MC improvement, correcting for age, disease duration, and dopaminergic therapy reduction; b) the correlation between HRQoL and NMF improvement, correcting for age, disease duration, motor and MC improvement. Results: Twenty patients were evaluated. Total NMF score significantly improved (44.6 %, [IQR = 18.3-100]; p = 0.022), particularly in Off condition (52.0 %, [IQR = 25.4-100]; p = 0.009); we observed strong correlation between NMF and MC improvement (Beta = 0.728; p = 0.006), mainly driven by the mitigation of unpredictable Off (Beta = 0.905; p < 0.001). Even after adjusting for potential confounders, the reduction of NMF independently correlated with increased HRQoL (Beta = 0.714; p = 0.010). Conclusions: STN-DBS demonstrated strong beneficial effect on NMF, resulting in significant improvement of HRQoL. This underlines the importance of recognizing NMF as a significant factor to be considered in the selection of patients eligible for STN-DBS.