Clinical Algorithm-Guided Approach to Botulinum Toxin Type A Treatment for Axial Postural Abnormalities in Parkinson's Disease

Background: Axial postural abnormalities (APAs) are common, disabling complications of Parkinson's disease (PD) with unclear pathophysiology. The presence of hyperactivity in multiple trunk muscles supports the use of botulinum toxin (BTA). However, its application is complex, due to the lack of standardized clinical and electrophysiological approach. Objectives: To evaluate BTA injections effectiveness using a clinical algorithm that integrates trunk angle severity and electromyography (EMG)-detected muscle hyperactivity in patients with APAs. Methods: This is prospective, open-label, pilot study. A novel decisional algorithm guided muscle selection, based on the bending degree and EMG findings. PD patients with different APAs underwent trunk angle measurement and EMG polygraphy of axial muscles in the standing position and during trunk activation. Primary outcome was the change in trunk misalignment measured before and one month after BTA injection. Secondary outcomes were the Clinical Global Impression of Change-Improvement (CGI-pain and CGI-posture) and the Numeric Rating Scale (NRS) for pain. Results: Among 52 PD patients, 20(38.5%) were eligible for treatment. At one-month follow-up, lateral trunk flexion (LTF) improved [LTF angle from 11.5 (CI 7.1-15.9) to 9.9, (CI 5.2-14.7) P = 0.013], while anterior trunk flexion (ATF) did not (thoracic fulcrum ATF from 41.4 to 40.6, P > 0.05; lumbar fulcrum ATF from 25.7 to 24.5, P > 0.05). CGI-posture improved in 45% of cases, CGI-pain improved in 50% of cases, and NRS decreased from 6.3 to 4.8 (P = 0.010). Conclusions: A clinical and neurophysiological algorithm integrating measures of trunk bending and EMG-detected muscle hyperactivity can optimize BTA treatment for APAs in PD, improving motor/ non-motor outcomes.