Objective: To propose a practical anatomo-functional framework for ultrasound-guided BoNT-A infiltration in upper limb tremor based on tremor biomechanics.

Background: Botulinum toxin type A (BoNT-A) is an established treatment for tremor refractory to oral pharmacological therapies. However, reported efficacy is variable and adverse effects—particularly excessive muscle weakness—remain frequent, likely due to non-targeted injection strategies.

Method: We report a case series of patients with proximal and distal upper limb tremor resistant to oral treatments, treated with ultrasound-guided BoNT-A injections following a structured anatomo-functional approach. Muscle selection and dose distribution were guided by biomechanical tremor patterns, with specific consideration of agonist–antagonist muscle balance.

Results: Treatment was associated with clinically meaningful tremor reduction and a low incidence of adverse effects. Proximal tremor patterns included: (1) internal rotation tremor involving pectoralis major and minor, subscapularis, and anterior deltoid; (2) lateral tremor involving supraspinatus and lateral deltoid; and (3) retroversion tremor involving infraspinatus, teres minor and major, and latissimus dorsi.

Distal tremor patterns included: (1) a flexor–extensor pattern involving flexor carpi ulnaris, palmaris longus, and flexor carpi radialis; and (2) a pronation–supination pattern primarily involving pronator teres. When elbow flexion–extension contributed to tremor, brachialis involvement was considered. Approximately 50% of the total BoNT-A dose was allocated to antagonist muscles

Conclusion: An anatomo-functional, ultrasound-guided approach to BoNT-A infiltration based on tremor biomechanics may improve both efficacy and safety. This framework provides a reproducible strategy for individualized tremor treatment.

Anatomo-Functional Tremor Patterns

References: 1.Salazar G, Caballero I. Ultrasound-Guided Botulinum Toxin Infiltrations in Essential Tremor Patients: A 36-week Follow Up. Tremor and Other Hyperkinetic Movements. 2025;15(1):8. DOI:10.5334/tohm.957 — demonstrating significant tremor improvement with ultrasound-guided IncobotulinumtoxinA and anatomo-physiological targeting.
Tremor and Other Hyperkinetic Movements

2.Motavasseli D, et al. Use of Botulinum Toxin in Upper-Limb Tremor: Systematic Review and Perspectives. Toxins (Basel). 2024;16(9):392 — highlights emerging evidence and the importance of targeted approaches.
MDPI

3.Botulinum Toxin Efficacy in Upper Limb Tremor: A Systematic Review and Meta-Analysis. (2025)* — meta-analysis supporting patient-tailored injection strategies.
PubMed

4.Eslamian F, et al. Effectiveness of Botulinum Toxin on Hand Tremor Intensity and Upper Limb Function in PD: Systematic Review. Tremor Other Hyperkinet Mov. 2023;13:27 — reviews guided approaches to minimize weakness.
Tremor and Other Hyperkinetic Movements

5.Samotus O, Lee J, Jog M. Developing a Reproducible BoNT-A Dosing Method for Upper Limb Tremor Using Kinematic Analysis. Toxins (Basel). 2021;13(4):264 — foundational evidence for customized dosing methods.

6. Ultrasound-Guided IncoBoNT Study (2025) — clinical evidence of ultrasound guidance increasing effectiveness and safety.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/proposal-of-anatomo-functional-tremor-patterns-for-ultrasound-guided-botulinum-toxin-infiltration/