The relationship between the cross-sectional area of the ulnar nerve and severity of ulnar neuropathy at the elbow: A systematic review

Background Ulnar neuropathy at the elbow (UNE) is the second most prevalent neuropathy of the upper extremity after median neuropathy. Although ultrasonography (US) is increasingly used in the diagnosis of UNE, it is not clear whether it can discriminate between stages of disease severity. This study aimed to investigate the correlation between ultrasonographic findings and UNE severity. Methods A systematic literature review was conducted according to PRISMA guidelines. PubMed, Embase, and Cochrane databases were searched to identify articles reporting on the relationship between US measurements and UNE severity, determined by either clinical symptoms or electrodiagnostic studies. The QUADAS-2 tool was used to assess risk of bias. Due to study variability, qualitative data synthesis was performed. Results In total, clinical data of 2165 patients, including US data of 2647 ulnar nerves, were represented in 15 studies. All studies evaluating the maximum cross-sectional area (CSA_MAX) in relation to either clinical or electrophysiological severity reported significant associations. Regarding CSA measurements at specific anatomical locations (i.e., the level of the medial epicondyle and proximal and distal to the medial epicondyle), mixed results were found. Conclusion Our findings support the value of CSA_MAX as an ultrasonographic marker for diagnosing UNE and assisting clinicians in grading its severity.