Enhancing diagnostic accuracy using a side‐to‐side cross‐sectional area ratio for the diagnosis of unilateral ulnar mononeuropathy at the elbow

• Published in: Muscle & nerve Vol. 63; no. 5; pp. 690 - 696
• Main Authors: Mamarabadi, Mansoureh, Morren, John A., Shook, Steven J.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01-05-2021; Wiley Subscription Services, Inc
• Subjects: Accuracy; Diagnosis; Diagnostic systems; Elbow; Elbow (anatomy); Entrapment; Forearm; Humerus; Medical diagnosis; nerve cross‐sectional area; neuromuscular ultrasound, ratio; Neuropathy; Peripheral nervous system; Sensitivity; side to side; ulnar neuropathy at the elbow; accuracy; nerve cross-sectional area; ulnar neuropathy at the elbow; neuromuscular ultrasound, ratio; side to side
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/mus.27178

Introduction
Neuromuscular ultrasonography (NMUS) is a valuable adjunct to electrodiagnostic testing for the diagnosis of entrapment neuropathy. The aim of this study was to determine whether diagnostic accuracy of NMUS could be enhanced in patients with unilateral ulnar mononeuropathy at the elbow (UNE) by utilizing side‐to‐side ulnar nerve cross‐sectional area (CSA) ratios.
Methods
Retrospective case‐control analysis of unilateral UNE cases identified cutoff values for elbow segment ulnar nerve maximum CSA (MCSA) of the symptomatic/asymptomatic limb (M ratio), as well as side‐to‐side ratios comparing MCSA with ipsilateral CSA at the Guyon canal (E/G), middle forearm (E/F), and middle humerus (E/H). Diagnostic accuracy values were calculated.
Results
The optimal M‐ratio cut‐off was 1.22 (sensitivity, 92.9%; specificity, 97.8%; accuracy, 95.4%). Optimal cutoffs for inter‐E/G, ‐E/F, and ‐E/H ratios were 1.07 (sensitivity, 98%; specificity, 78%; accuracy, 87.7%), 1.11 (sensitivity, 95%; specificity, 80%; accuracy, 87.2%), and 1.18 (sensitivity, 95%; specificity, 93%; accuracy, 94%), respectively.
Discussion
The M ratio and inter‐E/H ratio exhibited high diagnostic accuracy for unilateral UNE. Prospective studies are needed to compare the accuracy of the new measures with a single MCSA measurement.