Sonography of the Thenar Motor Branch of the Median Nerve: A Pictorial Review.

The thenar motor branch (TMB) of the median nerve exhibits significant anatomical variability, making it particularly vulnerable to iatrogenic injury during procedures such as carpal tunnel surgery. Understanding the diverse courses and origins of the TMB is critical for minimizing surgical complications. Such knowledge not only aids in preoperative planning but also enhances the accuracy of nerve conduction tests, contributing to improved postoperative outcomes. The ability to visualize and assess the TMB using imaging modalities like ultrasound represents a significant advancement in diagnostic and surgical preparation. Ultrasound is an accessible, cost-effective, and dynamic imaging technique that allows for real-time evaluation of neural structures. It provides detailed visualization of the TMB and its anatomical variations, offering valuable information that can guide surgical approaches and reduce the risk of injury to this vital branch. This article aims to provide a comprehensive overview of the anatomy, anatomical variants, and clinical significance of the TMB, with a particular focus on its assessment via ultrasound. Using high-resolution imaging, we demonstrate the application of ultrasound to identify the TMB in various configurations. Notably, the Lanz classification of the TMB is illustrated with ultrasound images, some of which, to our knowledge, are being presented for the first time. By integrating anatomical knowledge with advanced imaging techniques, this work emphasizes the importance of precise TMB evaluation, paving the way for safer surgical practices and enhanced patient outcomes.