Abstract
Post-stroke spasticity significantly impairs upper limb function and quality of life. Ultrasound-guided botulinum toxin-A (BoNT-A) injections have become a cornerstone of management, enhancing precision and safety. This paper offers a comprehensive guide for clinicians on ultrasound-guided BoNT-A injections for distal upper limb muscles. Each muscle is detailed in terms of its role in spasticity management, ultrasound identification with key anatomical landmarks, clinical relevance, and injection strategies. Motor points, traditionally identified through anatomical studies or electromyography (EMG), are precisely localized using a musculoskeletal ultrasound by targeting the point of maximum muscle thickness, often corresponding to the motor point. The authors present their clinical method, developed at Elias University Hospital (EUH), to refine BoNT-A injection practices. This approach enhances efficacy, reduces dosage requirements, and improves patient outcomes. The paper also explores unique ultrasound characteristics of spastic muscles, such as their relationship with peripheral nerves, adjacent vascular and muscular structures, and intra- and intermuscular fascia, to guide clinicians in targeting functional muscle tissue. This guide is illustrated with representative ultrasound images and clinical diagrams and provides practical insights into anatomical relationships and injection techniques. Part I focuses on distal upper limb muscles, with Part II addressing proximal upper limb muscles.