Objective: To investigate non-motor outcomes in patients with symmetric vs. asymmetric motor symptoms following subthalamic stimulation (STN-DBS) in Parkinson’s disease (PD).

Background: Motor asymmetry is a hallmark of PD, yet a relevant subgroup presents with symmetric motor signs. In a previous study from our group,¹ motor symmetry was associated with poorer activities of daily living (ADL) outcomes following STN-DBS, while quality of life (QoL) nevertheless improved and was unrelated to motor or ADL changes. This raises the question whether non-motor improvement contributes to QoL benefit, particularly in symmetric PD.

Method: In this prospective, international multicentre study with a 6-month follow-up, the primary outcome was the Non-Motor Symptoms Scale (NMSS). Secondary outcomes were the Scales for Outcomes in PD-Motor Scale (SCOPA-M) and the PD Questionnaire-8 (PDQ-8). Symmetric PD was defined as a right-to-left hemibody motor score of 1. Within-group changes were analysed using Wilcoxon signed-rank tests, between-group differences in NMSS change scores using Mann-Whitney U-tests. Associations between outcome parameters were examined using Spearman correlations.

Results: In total, 269 patients were included (64 symmetric, 205 asymmetric). NMSS total scores improved in both groups (symmetric: 64.5±42.9 to 45.0±31.7; asymmetric: 54.9±31.3 to 38.3± 26.6; both p<0.001). Both groups improved in sleep/fatigue, perceptual problems, and miscellaneous symptoms. Additional improvements in asymmetric PD included mood/apathy, gastrointestinal, and urinary symptoms. NMSS change scores did not differ between groups. Changes in NMSS total score correlated significantly with changes in the PDQ-8 Summary Index in both groups. In symmetric PD, PDQ-8 improvement was associated with changes in mood/apathy and perceptual symptoms, but not with SCOPA-M motor or ADL changes, whereas in asymmetric PD it was associated with broader non-motor, motor, and ADL changes.

Conclusion: Although non-motor improvement is broader in asymmetric PD, patients with symmetric PD also experience non-motor benefits after STN-DBS. The association between non-motor improvement and QoL may explain QoL benefit despite poor ADL outcomes in symmetric PD. These findings underscore the relevance of non-motor outcomes in preoperative counselling.

References: Jost ST, Atwani C, Loehrer PA, et al. Patients with symmetric Parkinson’s disease do poorly with subthalamic stimulation. Journal of Neurology, Neurosurgery & Psychiatry Published Online First: 04 March 2026. doi: 10.1136/jnnp-2025-336382

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MDS Abstracts - https://www.mdsabstracts.org/abstract/non-motor-symptom-improvement-as-a-driver-of-quality-of-life-after-subthalamic-stimulation-in-symmetric-parkinsons-disease/