Citation: Samotus, O.; Mahdi, Y.; Jog, M. Real-World Longitudinal Experience of Botulinum Toxin Therapy for Parkinson and Essential Tremor. Toxins 2022, 14, 557. https://doi.org/10.3390/ toxins14080557 Received: 20 June 2022 Accepted: 12 August 2022 Published: 17 August 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). toxins Article Real-World Longitudinal Experience of Botulinum Toxin Therapy for Parkinson and Essential Tremor Olivia Samotus 1,2 , Yekta Mahdi 1 and Mandar Jog 1,2, * 1 Department of Clinical Neurological Sciences, London Health Sciences Centre—Lawson Health Research Institute, 339 Windermere Road, A10-026, London, ON N6A 5A5, Canada 2 Schulich School of Medicine and Dentistry, University of Western, 1151 Richmond Street, London, ON N6A 3K7, Canada * Correspondence: mandar.jog@lhsc.on.ca Abstract: Background: Botulinum toxin type A (BoNT-A) therapy for upper-limb tremor has emerged as a promising option. However, it is unclear in real-world practices whether a technology-guided approach can compare with expert clinical assessments (including surface anatomy and palpation) for improving outcomes. This retrospective study aims to review our clinical outcomes of treating essential tremor (ET) and Parkinson’s disease (PD) tremor using either clinical- or kinematic-based injection pattern determination methods. Methods: 68 ET and 45 PD patients received at least one injection for their upper-limb tremor (unilateral or bilateral) in the last 7 years. Demographics of patients and BoNT-A injections were collected. A Mann–Whitney U statistical test was used to compare outcome measures between ET and PD cohorts. Results: Mean age (72 ± 9 years), number of injections (5), years receiving therapy (~2 years), clinic- (~57%) or kinematic-based patterns, and self-paying (52%) were similar between both cohorts. BoNT-A as a monotherapy in both upper limbs was received in more ET than PD patients. Double reconstitution of Xeomin ® in the wrist flexors/extensors, supinator, biceps, and triceps were most injected. Discontinuation due to no benefit/weakness was not dependent on the injection pattern determination approach. Conclusions: Kinematic-based BoNT-A injections produced similar treatment outcomes to injections based on the clinical expertise of the expert injector. This suggests that kinematics could be used by a non-expert to attain equivalent efficacy potentially improving access to this treatment. Keywords: Botulinum toxin; upper-limb tremor; treatment; essential tremor; Parkinson’s disease Key Contribution: Botulinum toxin injection patterns determined using either clinical/visual assess- ment by an expert injector or a kinematic-based approach produced similar treatment outcomes in a real-world clinical setting. 1. Introduction Upper-limb tremor often interferes with daily activities, impacts social lifestyles, and reduces the quality of life in essential tremor (ET) and Parkinson’s disease (PD) pa- tients [1–3]. Oral medications, such as beta blockers for ET patients and dopaminergic replacement therapy (DRT) for PD patients, provide suboptimal benefit [4–8]. Approx- imately 30% of PD patients are refractory to DRT, and 60% of ET patients discontinue oral medications due to failure to alleviate tremor and side effects [4,6,9–11]. Botulinum toxin type A (BoNT-A) as a targeted tremor therapy holds promise when personalizing injection patterns (selection of muscle and dose) to the characteristics of an individual’s tremor [9,12–15]. Objective techniques to personalize injection pattern determination in- clude using kinematic technology that measures the severity (selection of dose) and the contribution of tremor in all the upper limb joints (selection of muscles) or using the Yale method that involves measuring rhythmic burst potentials of electromyographic (EMG) Toxins 2022, 14, 557. https://doi.org/10.3390/toxins14080557 https://www.mdpi.com/journal/toxins