Patients with symmetric PD can be identified with a simple and straightforward method, a ratio right by left hemibody score equalling 1. This requires no additional time, effort or specialised neuroimaging or laboratory resources.
Background Motor asymmetry is a hallmark of Parkinson’s disease (PD), but ~20% of patients present with symmetric motor signs, which are associated with faster disease progression and poorer dopaminergic response. The impact of motor symmetry on activities of daily living (ADL) outcomes following subthalamic deep brain stimulation (STN-DBS) remains unclear. We hypothesised that patients with symmetric PD experience less ADL improvement post-STN-DBS than asymmetric PD patients.
Methods This was a prospective, quasi-experimental, non-randomised, controlled, international multicentre study with a 6-month follow-up. The primary outcome was the Scales for Outcomes in Parkinson’s Disease-Motor ADL scale. Secondary outcomes included Unified Parkinson’s Disease Rating Scale motor examination and Parkinson’s Disease Questionnaire-8 (PDQ-8). We defined symmetric PD as a right-to-left hemibody motor score equalling 1. We analysed within-group longitudinal changes, between-group outcome differences, effect size and correlations between PDQ-8 and motor changes. We confirmed results in a propensity-score matched subcohort with well-balanced demographic and clinical parameters.
Results We included 200 patients with asymmetric and 54 with symmetric PD. In symmetric PD, ADL remained stable, which was not associated with the observed PDQ-8 improvement. In contrast, in asymmetric PD, ADL improved with a moderate effect size, which correlated moderately with PDQ-8 improvement. In symmetric PD, the absolute risk of experiencing no clinically relevant postoperative ADL improvement was 23.8% higher.